Sci Adv , IF:13.116 , 2020 Dec , V6 (50) doi: 10.1126/sciadv.abc8895
Functional innovations of PIN auxin transporters mark crucial evolutionary transitions during rise of flowering plants.
Institute of Science and Technology (IST) Austria, 3400 Klosterneuburg, Austria.; Institute of Science and Technology (IST) Austria, 3400 Klosterneuburg, Austria. jiri.friml@ist.ac.at.
Flowering plants display the highest diversity among plant species and have notably shaped terrestrial landscapes. Nonetheless, the evolutionary origin of their unprecedented morphological complexity remains largely an enigma. Here, we show that the coevolution of cis-regulatory and coding regions of PIN-FORMED (PIN) auxin transporters confined their expression to certain cell types and directed their subcellular localization to particular cell sides, which together enabled dynamic auxin gradients across tissues critical to the complex architecture of flowering plants. Extensive intraspecies and interspecies genetic complementation experiments with PINs from green alga up to flowering plant lineages showed that PIN genes underwent three subsequent, critical evolutionary innovations and thus acquired a triple function to regulate the development of three essential components of the flowering plant Arabidopsis: shoot/root, inflorescence, and floral organ. Our work highlights the critical role of functional innovations within the PIN gene family as essential prerequisites for the origin of flowering plants.
PMID: 33310852
Dev Cell , IF:10.092 , 2020 Dec , V55 (5) : P603-616.e5 doi: 10.1016/j.devcel.2020.10.019
Regulation of ARGONAUTE10 Expression Enables Temporal and Spatial Precision in Axillary Meristem Initiation in Arabidopsis.
Guangdong Provincial Key Laboratory for Plant Epigenetics, College of Life Sciences and Oceanography, Shenzhen University, Shenzhen 518060, China; Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China; Department of Botany and Plant Sciences, Institute of Integrative Genome Biology, University of California, Riverside, CA 92521, USA.; Department of Botany and Plant Sciences, Institute of Integrative Genome Biology, University of California, Riverside, CA 92521, USA.; State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, and National Center for Plant Gene Research, Beijing 100101, China.; Guangdong Provincial Key Laboratory for Plant Epigenetics, College of Life Sciences and Oceanography, Shenzhen University, Shenzhen 518060, China; Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China.; Department of Botany and Plant Sciences, Institute of Integrative Genome Biology, University of California, Riverside, CA 92521, USA. Electronic address: xuemei.chen@ucr.edu.
Axillary meristems (AMs) give rise to lateral shoots and are critical to plant architecture. Understanding how developmental cues and environmental signals impact AM development will enable the improvement of plant architecture in agriculture. Here, we show that ARGONAUTE10 (AGO10), which sequesters miR165/166, promotes AM development through the miR165/166 target gene REVOLUTA. We reveal that AGO10 expression is precisely controlled temporally and spatially by auxin, brassinosteroids, and light to result in AM initiation only in the axils of leaves at a certain age. AUXIN RESPONSE FACTOR 5 (ARF5) activates while BRASSINAZOLE-RESISTANT 1 (BZR1) and PHYTOCHROME-INTERACTING FACTOR 4 (PIF4) repress AGO10 transcription directly. In axils of young leaves, BZR1 and PIF4 repress AGO10 expression to prevent AM initiation. In axils of older leaves, ARF5 upregulates AGO10 expression to promote AM initiation. Our results uncover the spatiotemporal control of AM development through the cooperation of hormones and light converging on a regulator of microRNA.
PMID: 33232670
Curr Biol , IF:9.601 , 2020 Dec , V30 (24) : P4857-4868.e6 doi: 10.1016/j.cub.2020.09.037
A WOX/Auxin Biosynthesis Module Controls Growth to Shape Leaf Form.
Department of Comparative Development and Genetics, Max Planck Institute for Plant Breeding Research, Carl-von-Linne-Weg 10, 50829 Cologne, Germany.; Umea Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, 90183 Umea, Sweden; Laboratory of Growth Regulators, Institute of Experimental Botany of the Czech Academy of Sciences and Faculty of Science of Palacky University, Slechtitelu 27, 78371 Olomouc, Czech Republic.; Umea Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, 90183 Umea, Sweden.; Department of Comparative Development and Genetics, Max Planck Institute for Plant Breeding Research, Carl-von-Linne-Weg 10, 50829 Cologne, Germany. Electronic address: tsiantis@mpipz.mpg.de.
A key challenge in biology is to understand how the regional control of cell growth gives rise to final organ forms. Plant leaves must coordinate growth along both the proximodistal and mediolateral axes to produce their final shape. However, the cell-level mechanisms controlling this coordination remain largely unclear. Here, we show that, in A. thaliana, WOX5, one of the WUSCHEL-RELATED HOMEOBOX (WOX) family of homeobox genes, acts redundantly with WOX1 and WOX3 (PRESSED FLOWER [PRS]) to control leaf shape. Through genetics and hormone measurements, we find that these WOXs act in part through the regional control of YUCCA (YUC) auxin biosynthetic gene expression along the leaf margin. The requirement for WOX-mediated YUC expression in patterning of leaf shape cannot be bypassed by the epidermal expression of YUC, indicating that the precise domain of auxin biosynthesis is important for leaf form. Using time-lapse growth analysis, we demonstrate that WOX-mediated auxin biosynthesis organizes a proximodistal growth gradient that promotes lateral growth and consequently the characteristic ellipsoid A. thaliana leaf shape. We also provide evidence that WOX proteins shape the proximodistal gradient of differentiation by inhibiting differentiation proximally in the leaf blade and promoting it distally. This regulation allows sustained growth of the blade and enables a leaf to attain its final form. In conclusion, we show that the WOX/auxin regulatory module shapes leaf form by coordinating growth along the proximodistal and mediolateral leaf axes.
PMID: 33035489
Curr Biol , IF:9.601 , 2020 Dec , V30 (24) : P4999-5006.e3 doi: 10.1016/j.cub.2020.09.036
Intrinsic Cell Polarity Coupled to Growth Axis Formation in Tobacco BY-2 Cells.
John Innes Centre, Colney Lane, Norwich NR4 7UH, UK. Electronic address: jordi.chan@jic.ac.uk.; John Innes Centre, Colney Lane, Norwich NR4 7UH, UK.; John Innes Centre, Colney Lane, Norwich NR4 7UH, UK. Electronic address: enrico.coen@jic.ac.uk.
Several plant proteins are preferentially localized to one end of a cell, allowing a polarity to be assigned to the cell. These cell polarity proteins often exhibit coordinated patterns between neighboring cells, termed tissue cell polarity. Tissue cell polarity is widespread in plants and can influence how cells grow, divide, and differentiate [1-5]. However, it is unclear whether cell polarity is established through cell-intrinsic or -extrinsic mechanisms and how polarity is coupled to growth. To address these issues, we analyzed the behavior of a tissue cell polarity protein BASL (BREAKING OF ASYMMETRY IN THE STOMATAL LINEAGE) in the simplifying context of cultured cell filaments and in protoplasts before and during regeneration. We show that BASL is polarly localized when ectopically expressed in tobacco BY-2 cell cultures. Ectopic BASL is found preferentially at the developing tips of cell filaments, likely marking a polarized molecular address. Polarity can shift during the cell cycle and is resistant to treatment with microtubule, actin or auxin transport inhibitors. BASL also exhibits polar localization in spherical protoplasts, in contrast to other polarity proteins so far tested. BASL polarity within protoplasts is dynamic and resistant to auxin transport inhibitors. As protoplasts regenerate, polarity remains dynamic in isotropically growing cells but becomes fixed in anisotropic cells and aligns with the axis of cell growth. Our findings suggest that plant cells have an intrinsic ability to polarize and that environmental or developmental cues may act by biasing the direction of this polarity and thus the orientation of anisotropic growth.
PMID: 33035485
Curr Biol , IF:9.601 , 2020 Dec , V30 (23) : P4654-4664.e4 doi: 10.1016/j.cub.2020.09.013
A Plasma Membrane Nanodomain Ensures Signal Specificity during Osmotic Signaling in Plants.
BPMP, Univ Montpellier, CNRS, INRAE, Institut Agro, Montpellier, France.; Laboratoire Reproduction et Developpement des Plantes, Universite Lyon, Ecole Normale Superieure de Lyon, Universite Claude Bernard Lyon 1, Centre National de la Recherche Scientifique, Institut National de Recherche pour l'Agriculture, l'Alimentation et l'Environnement, F-69342 Lyon, France.; Centre de Biochimie Structurale, Centre National de la Recherche Scientifique Unite Mixte de Recherche 5048, Institut National de la Sante et de la Recherche Medicale U1054, Universite de Montpellier, 34090 Montpellier, France.; BPMP, Univ Montpellier, CNRS, INRAE, Institut Agro, Montpellier, France. Electronic address: alexandre.martiniere@cnrs.fr.
In the course of their growth and development, plants have to constantly perceive and react to their environment. This is achieved in cells by the coordination of complex combinatorial signaling networks. However, how signal integration and specificity are achieved in this context is unknown. With a focus on the hyperosmotic stimulus, we use live super-resolution light imaging methods to demonstrate that a Rho GTPase, Rho-of-Plant 6 (ROP6), forms stimuli-dependent nanodomains within the plasma membrane (PM). These nanodomains are necessary and sufficient to transduce production of reactive oxygen species (ROS) that act as secondary messengers and trigger several plant adaptive responses to osmotic constraints. Furthermore, osmotic signal triggers interaction between ROP6 and two NADPH oxidases that subsequently generate ROS. ROP6 nanoclustering is also needed for cell surface auxin signaling, but short-time auxin treatment does not induce ROS accumulation. We show that auxin-induced ROP6 nanodomains, unlike osmotically driven ROP6 clusters, do not recruit the NADPH oxidase, RBOHD. Together, our results suggest that Rho GTPase nano-partitioning at the PM ensures signal specificity downstream of independent stimuli.
PMID: 33035478
Proc Natl Acad Sci U S A , IF:9.412 , 2020 Dec doi: 10.1073/pnas.2015400117
Glucose-TOR signaling regulates PIN2 stability to orchestrate auxin gradient and cell expansion in Arabidopsis root.
Shanghai Centre for Plant Stress Biology, Chinese Academy of Sciences Centre for Excellence in Molecular Plant Sciences, Chinese Academy of Sciences, Shanghai 201602, People's Republic of China.; Basic Forestry and Proteomics Research Centre, Haixia Institute of Science and Technology, Fujian Agriculture and Forestry University, 350002 Fujian, People's Republic of China.; University of Chinese Academy of Sciences, 100049 Beijing, People's Republic of China.; Basic Forestry and Proteomics Research Centre, Haixia Institute of Science and Technology, Fujian Agriculture and Forestry University, 350002 Fujian, People's Republic of China; yanxiong@fafu.edu.cn.
The plant growth hormone auxin controls cell identity, cell division, and expansion. In the primary root of Arabidopsis there is a robust auxin gradient with a peak concentration at the tip of the meristem and a significant decrease throughout the elongation zone. The molecular mechanisms of how such a steep auxin gradient is established and maintained, and how this auxin gradient within the root dynamically adjusts in response to environmental stimuli are still largely unknown. Here, using a large-scale Arabidopsis mutant screening, we described the identification of PIN2 (PIN-FORMED 2), an auxin efflux facilitator, as a key downstream regulator in glucose-TOR (target of rapamycin) energy signaling. We demonstrate that glucose-activated TOR phosphorylates and stabilizes PIN2 and therefore influences the gradient distribution of PIN2 in the Arabidopsis primary root. Interestingly, dysregulation of TOR or PIN2 disrupts the glucose-promoted low auxin region located in the elongation zone that is essential for cell elongation. Taken together, our results shed light on how carbon and metabolic status can be tightly integrated with the hormone-driven processes to orchestrate complex plant growth programs.
PMID: 33288701
Proc Natl Acad Sci U S A , IF:9.412 , 2020 Dec , V117 (49) : P31500-31509 doi: 10.1073/pnas.2013305117
The Arabidopsis NRT1/PTR FAMILY protein NPF7.3/NRT1.5 is an indole-3-butyric acid transporter involved in root gravitropism.
RIKEN Center for Sustainable Resource Science, Kanagawa 230-0045, Japan.; Graduate School of Science and Technology, Nara Institute of Science and Technology, Nara 630-0192, Japan.; Department of Biological Production Science, United Graduate School of Agricultural Science, Tokyo University of Agriculture and Technology, Tokyo 183-8509, Japan.; Institute of Global Innovation Research, Tokyo University of Agriculture and Technology, Tokyo 183-8509, Japan.; Department of Biochemistry, Okayama University of Science, Okayama 700-0005, Japan.; RIKEN Center for Sustainable Resource Science, Kanagawa 230-0045, Japan; mitsunori.seo@riken.jp.
Active membrane transport of plant hormones and their related compounds is an essential process that determines the distribution of the compounds within plant tissues and, hence, regulates various physiological events. Here, we report that the Arabidopsis NITRATE TRANSPORTER 1/PEPTIDE TRANSPORTER FAMILY 7.3 (NPF7.3) protein functions as a transporter of indole-3-butyric acid (IBA), a precursor of the major endogenous auxin indole-3-acetic acid (IAA). When expressed in yeast, NPF7.3 mediated cellular IBA uptake. Loss-of-function npf7.3 mutants showed defective root gravitropism with reduced IBA levels and auxin responses. Nevertheless, the phenotype was restored by exogenous application of IAA but not by IBA treatment. NPF7.3 was expressed in pericycle cells and the root tip region including root cap cells of primary roots where the IBA-to-IAA conversion occurs. Our findings indicate that NPF7.3-mediated IBA uptake into specific cells is required for the generation of appropriate auxin gradients within root tissues.
PMID: 33219124
New Phytol , IF:8.512 , 2020 Dec doi: 10.1111/nph.17152
Auxin efflux controls orderly nucellar degeneration and expansion of the female gametophyte in Arabidopsis.
State Key Laboratory of Crop Stress Biology for Arid Areas, College of Agronomy, Northwest A&F University, Yangling, Shaanxi, 712100, China.; Department of Biochemistry and Molecular Biology, University of Massachusetts, Amherst, Massachusetts, 01003, USA.; State Key Laboratory of Crop Stress Biology for Arid Areas, College of Horticulture, Northwest A&F University, Yangling, Shaanxi, 712100, China.; Ministry of Education Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou, Gansu, 730000, China.
The nucellus tissue in flowering plants provides nutrition for the development of the female gametophyte (FG) and young embryo. The nucellus degenerates as the FG develops, but the mechanism controlling the coupled process of nucellar degeneration and FG expansion remains largely unknown. The degeneration process of the nucellus and spatiotemporal auxin distribution in the developing ovule before fertilization were investigated in Arabidopsis thaliana. Nucellar degeneration before fertilization occurs through vacuolar cell death and in a ordered degeneration fashion. This sequential nucellar degeneration is controlled by the signalling molecule auxin. Auxin efflux plays the core role in precisely controlling the spatiotemporal pattern of auxin distribution in the nucellus surrounding the FG. The auxin efflux carrier PIN1 transports maternal auxin into the nucellus while PIN3/PIN4/PIN7 further delivers auxin to degenerating nucellar cells and concurrently controls FG central vacuole expansion. Notably, auxin level and auxin efflux are controlled by the maternal tissues, acting as a key communication from maternal to filial tissue.
PMID: 33338267
Curr Opin Plant Biol , IF:8.356 , 2020 Dec , V59 : P101975 doi: 10.1016/j.pbi.2020.10.007
MIXTAs and phytohormones orchestrate cotton fiber development.
Zhejiang Provincial Key Laboratory of Crop Genetic Resources, Institute of Crop Science, College of Agriculture and Biotechnology, Zhejiang University, 310029 Zhejiang, PR China; National Key Laboratory of Crop Genetics and Germplasm Enhancement, Nanjing Agricultural University, Nanjing 210095, PR China.; Zhejiang Provincial Key Laboratory of Crop Genetic Resources, Institute of Crop Science, College of Agriculture and Biotechnology, Zhejiang University, 310029 Zhejiang, PR China. Electronic address: cotton@zju.edu.cn.
Cotton is the largest source of natural fiber for textile industry in the world. Cotton fibers are seed trichomes that make cotton unique among plants. Cotton fibers originate from ovule epidermal cells and serve as an excellent model to study the process of cell differentiation in plants. Characterization of factors contributing to fiber development will help to reveal general mechanisms of cell differentiation in plants. Transcription factors (TFs), especially MYB-MIXTA-like (MML) factors, appear to have evolved unique roles in fiber development. In addition, phytohormones including brassinosteroids, jasmonic acid, GA and auxin also play an important role in regulating fiber development. Here, we summarize the mechanisms of MIXTAs and phytohormones orchestrating cotton fiber development. The progress in understanding molecular basis of fiber development will facilitate future genetic engineering and breeding to improve cotton fiber quality and yield.
PMID: 33296746
Plant Biotechnol J , IF:8.154 , 2020 Dec doi: 10.1111/pbi.13531
A novel motif in the 5'-UTR of an orphan gene 'Big Root Biomass' modulates root biomass in sesame.
Oil Crops Research Institute of the Chinese Academy of Agricultural Sciences, Key Laboratory of Biology and Genetic Improvement of Oil Crops, Ministry of Agriculture and Rural Affairs, No.2 Xudong 2nd Road, Wuhan, 430062, China.; Laboratory of Genetics, Horticulture and Seed Sciences, Faculty of Agronomic Sciences, University of Abomey-Calavi, 01 BP 526, Cotonou, Republic of Benin.
Developing crops with improved root system is crucial in current global warming scenario. Underexploited crops are valuable reservoirs of unique genes that can be harnessed for the improvement of major crops. In this study, we performed genome-wide association studies on seven root traits in sesame (Sesamum indicum L.) and uncovered 409 significant signals, 19 quantitative trait loci containing 32 candidate genes. A peak SNP significantly associated with root number and root dry weight traits was located in the promoter of the gene named 'Big Root Biomass' (BRB), which was subsequently validated in a bi-parental population. BRB has no functional annotation and is restricted to the Lamiales order. We detected the presence of a novel motif 'AACACACAC' located in the 5'-UTR of BRB in single and duplicated copy in accessions with high and small root biomass, respectively. A strong expression level of BRB was negatively correlated with high root biomass and this was attributed to the gene SiMYB181 which represses the activity of BRB by binding specifically to the single motif but not to the duplicated one. Curiously, the allele that enhanced BRB expression has been intensively selected by modern breeding. Overexpression of BRB in Arabidopsis modulates auxin pathway leading to reduced root biomass, improved yield parameters under normal growth conditions and increased drought stress sensitivity. Overall, BRB represents a solid gene model for improving the performance of sesame and other crops.
PMID: 33369837
Cold Spring Harb Perspect Biol , IF:7.64 , 2020 Dec doi: 10.1101/cshperspect.a039974
Auxin and Flower Development: A Blossoming Field.
Dipartimento di Bioscienze, Universita degli Studi di Milano, 20133 Milan, Italy.; Max Planck Institute for Plant Breeding Research, 50829 Cologne, Germany.
The establishment of the species-specific floral organ body plan involves many coordinated spatiotemporal processes, which include the perception of positional information that specifies floral meristem and floral organ founder cells, coordinated organ outgrowth coupled with the generation and maintenance of inter-organ and inter-whorl boundaries, and the termination of meristem activity. Auxin is integrated within the gene regulatory networks that control these processes and plays instructive roles at the level of tissue-specific biosynthesis and polar transport to generate local maxima, perception, and signaling. Key features of auxin function in several floral contexts include cell nonautonomy, interaction with cytokinin gradients, and the central role of MONOPTEROS and ETTIN to regulate canonical and noncanonical auxin response pathways, respectively. Arabidopsis flowers are not representative of the enormous angiosperm floral diversity; therefore, comparative studies are required to understand how auxin underlies these developmental differences. It will be of great interest to compare the conservation of auxin pathways among flowering plants and to discuss the evolutionary role of auxin in floral development.
PMID: 33355218
Sci Total Environ , IF:6.551 , 2020 Dec , V757 : P143994 doi: 10.1016/j.scitotenv.2020.143994
Adaptive roots of mangrove Avicennia marina: Structure and gene expressions analyses of pneumatophores.
Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystem, College of the Environment and Ecology, Xiamen University, Xiamen, Fujian 361102, China.; Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystem, College of the Environment and Ecology, Xiamen University, Xiamen, Fujian 361102, China; Graduate College of Biomedical Sciences, Western University of Health Sciences, Pomona, CA 91766, USA.; Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystem, College of the Environment and Ecology, Xiamen University, Xiamen, Fujian 361102, China; Graduate College of Biomedical Sciences, Western University of Health Sciences, Pomona, CA 91766, USA. Electronic address: liqq@xmu.edu.cn.
The Avicennia marina is a mangrove species widely distributed throughout the tropical and subtropical intertidal wetlands. To adapt to adverse tidal waves and hypoxia environments, A. marina has evolved a sophisticated root system to better secure itself on the muddy soil with downward-grown anchor roots and upward-grown aerial roots, called pneumatophores. However, the process behind the development of a negative-gravitropic pneumatophore is not understood. Paraffin sections reveal anatomical differences among the shoots, anchor roots, and gas exchanging pneumatophores, clearly reflecting their functional diversions. The pneumatophore, in particular, contains abundant aerenchyma tissues and a thin cap structure at the tip. Transcriptomic analyses of both anchor roots and pneumatophores were performed to elucidate gene expression dynamics during the formation of pneumatophores. The results show that the plant hormone auxin regulates multiple different root initiations. The auxin related gene IAA19 plays a key role in pneumatophore development while the interaction of ethylene and abscisic acid is important for aerenchyma formation. Moreover, the molecular mechanisms behind pneumatophore anti-gravitropic growth may be regulated by the reduced strength of the statolith formation signaling pathway. These results shed light on the mechanistic understanding of pneumatophore formation in mangrove plants.
PMID: 33316524
Plant Cell Environ , IF:6.362 , 2020 Dec doi: 10.1111/pce.13983
Dynamics of miRNA mediated regulation of legume symbiosis.
National Institute of Plant Genome Research, New Delhi, India.
Symbiotic nitrogen fixation in legume nodules is important in soils with low nitrogen availability. The initiation and sustainability of symbiosis requires cellular reprogramming that involves the miRNA-mediated inhibition or activation of specific nodulation genes. The high-throughput sequencing of small RNA libraries has identified miRNAs and their targets, which are the major players in the post-transcriptional gene regulation (PTGS) of the different stages of legume-rhizobia symbiosis ranging from bacterial colonization and organogenesis to symbiotic nitrogen fixation. Here we present an overview of information obtained from the miRNA libraries from nodulating tissues that have been sequenced to date. The functional analysis of miRNAs has revealed roles in phytohormone homeostasis and spatio-temporal regulation, as well as the mobility of miRNAs and their functions in shoot to root signalling that affects diverse functions, including bacterial entry, meristem division and differentiation, nitrogen fixation and senescence. Furthermore, small RNA fragments of rhizobial origin repress complementary plant mRNAs. We also consider the roles of miRNAs in determinate or indeterminate nodules. Taken together, this overview confirms that miRNAs are master regulators of the legume-rhizobia symbiosis. This article is protected by copyright. All rights reserved.
PMID: 33347631
PLoS Pathog , IF:6.218 , 2020 Dec , V16 (12) : Pe1009118 doi: 10.1371/journal.ppat.1009118
Auxin response factors (ARFs) differentially regulate rice antiviral immune response against rice dwarf virus.
The State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing, China.; Department of Biology, Southern University of Science and Technology, Shenzhen, China.; State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, South China Agricultural University, Guangzhou, China.
There are 25 auxin response factors (ARFs) in the rice genome, which play critical roles in regulating myriad aspects of plant development, but their role (s) in host antiviral immune defense and the underneath mechanism remain largely unknown. By using the rice-rice dwarf virus (RDV) model system, here we report that auxin signaling enhances rice defense against RDV infection. In turn, RDV infection triggers increased auxin biosynthesis and accumulation in rice, and that treatment with exogenous auxin reduces OsIAA10 protein level, thereby unleashing a group of OsIAA10-interacting OsARFs to mediate downstream antiviral responses. Strikingly, our genetic data showed that loss-of-function mutants of osarf12 or osarf16 exhibit reduced resistance whereas osarf11 mutants display enhanced resistance to RDV. In turn, OsARF12 activates the down-stream OsWRKY13 expression through direct binding to its promoter, loss-of-function mutants of oswrky13 exhibit reduced resistance. These results demonstrated that OsARF 11, 12 and 16 differentially regulate rice antiviral defense. Together with our previous discovery that the viral P2 protein stabilizes OsIAA10 protein via thwarting its interaction with OsTIR1 to enhance viral infection and pathogenesis, our results reveal a novel auxin-IAA10-ARFs-mediated signaling mechanism employed by rice and RDV for defense and counter defense responses.
PMID: 33264360
Plant J , IF:6.141 , 2020 Dec doi: 10.1111/tpj.15112
Phytohormones in Fruit Development and Maturation.
Section of Plant Breeding and Genetics, School of Integrative Plant Sciences, Cornell University, Ithaca, NY, 14853, USA.; United States Department of Agriculture - Agricultural Research Service and Boyce Thompson Institute for Plant Research, Cornell University campus, Ithaca, NY, 14853, USA.
Phytohormones are integral to the regulation of fruit development and maturation. This review expands upon current understanding of the relationship between hormone signaling and fruit development, emphasizing fleshy fruit and highlighting recent work in the model crop tomato and additional species. Fruit development comprises fruit set initiation, growth, and maturation and ripening. Fruit set transpires after fertilization and is associated with auxin and gibberellic acid (GA) signaling. Interaction between auxin and GAs, as well as other phytohormones, is mediated by auxin-responsive Aux/IAA and ARF proteins. Fruit growth consists of cell division and expansion, the former shown to be influenced by auxin signaling. While regulation of cell expansion is less thoroughly understood, evidence indicates synergistic regulation via both auxin and GAs, with input from additional hormones. Fruit maturation, a transitional phase that precipitates ripening, occurs when auxin and GA levels subside with a concurrent rise in abscisic acid (ABA) and ethylene. During fruit ripening, ethylene plays a clear role in climacteric fruits, whereas non-climacteric ripening is generally associated with ABA. Recent evidence indicates varying requirements for both hormones within both ripening physiologies, suggesting rebalancing and specification of roles for common regulators rather than reliance upon one. Numerous recent discoveries pertaining to the molecular basis of hormonal activity and cross-talk are discussed, while we also note that many questions remain such as the molecular basis of additional hormonal activities, the role of epigenome changes and how prior discoveries translate to the plethora of angiosperm species.
PMID: 33274492
J Exp Bot , IF:5.908 , 2020 Dec doi: 10.1093/jxb/eraa590
Fruit presence induces polar auxin transport in citrus and olive stem and represses IAA release from the bud.
Department of Fruit Tree Sciences, The Institute of Plant Sciences, Agricultural Research Organization, The Volcani Center, Rishon LeZion, Israel.; The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, The Robert H Smith Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Rehovot, Israel.; CEBAS-CSIC, Department of Plant Nutrition, Campus Universitario de Eapinardo, Espinardo, Murcia, Spain.
In many fruit trees, heavy fruit load in one year reduces flowering in the following year, creating a biennial fluctuation in yield termed alternate bearing AB). In subtropical trees, where flowering induction is mostly governed by the accumulation of chilling hours, fruit load is thought to generate a signal (AB signal) that blocks the perception of the cold induction. Fruit removal during a heavy-fruit-load year (On-Crop) is effective at inducing flowering only if performed one to a few months prior to onset of the flowering induction period. We previously showed that following fruit removal, content of the auxin indoleacetic acid (IAA) in citrus buds is reduced, suggesting that the hormone plays a role in the AB signal. Here, we demonstrate that fruit presence generates relatively strong polar auxin transport (PAT) in citrus and olive stems. Upon fruit removal, PAT is reduced and allows auxin release from the bud. Furthermore, using immunolocalization, hormone and gene expression analyses, we show that in citrus, IAA level in the bud and, specifically, in the apical meristem is reduced upon fruit removal. Overall, our data provide support for the notion that fruit presence generates an auxin signal in the bud which may affect flowering induction.
PMID: 33345278
J Exp Bot , IF:5.908 , 2020 Dec doi: 10.1093/jxb/eraa572
WUSCHEL in the shoot apical meristem: old player, new tricks.
Plant Stress Signaling, Instituto Gulbenkian de Ciencia, Rua da Quinta Grande, Oeiras, Portugal.; Laboratoire Reproduction et Developpement des Plantes, Universite de Lyon, Ecole Normale Superieure de Lyon, UCB Lyon, CNRS, INRAE, Lyon Cedex, France.
The maintenance of the stem cell niche in the shoot apical meristem, the structure that generates all of the aerial organs of the plant, relies on a canonical feedback loop between WUSCHEL (WUS) and CLV3 (CLV3). WUS is a homeodomain transcription factor expressed in the organizing center that moves to the central zone to promote stem cell fate. CLAVATA3 is a peptide whose expression is induced by WUS in the central zone that can move back to the organizing center to inhibit WUS expression. Within the last 20 years since the initial formulation of the CLV/WUS feedback loop, the mechanisms of stem cell maintenance have been intensively studied and the function of WUS has been redefined. In this review, we will highlight the most recent advances in our comprehension of the molecular mechanisms of WUS function, of its interaction with other transcription factors and with hormonal signals and of its connection to environmental signals. Through this, we will show how WUS can integrate both internal and external cues to adapt meristem function to the plant environment.
PMID: 33332559
J Exp Bot , IF:5.908 , 2020 Dec doi: 10.1093/jxb/eraa479
Regulation of glucosinolate biosynthesis.
Institute for Plant Sciences and Cluster of Excellence on Plant Sciences (CEPLAS), University of Cologne, Cologne, Germany.
Glucosinolates are secondary defense metabolites produced by plants of the order Brassicales, which includes the model species Arabidopsis and many crop species. In the past 13 years, the regulation of glucosinolate synthesis in plants has been intensively studied, with recent research revealing complex molecular mechanisms that connect glucosinolate production with responses to other central pathways. In this review, we discuss how the regulation of glucosinolate biosynthesis is ecologically relevant for plants, how it is controlled by transcription factors, and how this transcriptional machinery interacts with hormonal, environmental, and epigenetic mechanisms. We present the central players in glucosinolate regulation, MYB and basic helix-loop-helix transcription factors, as well as the plant hormone jasmonate, which together with other hormones and environmental signals allow the coordinated and rapid regulation of glucosinolate genes. Furthermore, we highlight the regulatory connections between glucosinolates, auxin, and sulfur metabolism and discuss emerging insights and open questions on the regulation of glucosinolate biosynthesis.
PMID: 33313802
J Exp Bot , IF:5.908 , 2020 Dec doi: 10.1093/jxb/eraa565
ZmCLA4 regulates leaf angle through multiple hormone signaling pathways in maize.
College of Agronomy, Synergetic Innovation Center of Henan Grain Crops and National Key Laboratory of Wheat and Maize Crop Science, Henan Agricultural University, Longzihu University Park, Zhengdong New Area, Zhengzhou, Henan, China.; Henan Academy of Agricultural Science, Zhengzhou, Henan, China.
Leaf angle (LA) is an important agronomic trait in cereals that shares a close relationship with crop architecture and grain yield. Although it has been previously reported that ZmCLA4 can influence LA, the underlying mechanism of it remains unclear. In this study, we used Gal4-LexA/UAS system and transactivation analysis to demonstrate that ZmCLA4 is a transcriptional repressor that regulates LA. DNA affinity purification sequencing (DAP-Seq) analysis revealed that ZmCLA4 mainly binds to the promoters containing the EAR motif (CACCGGAC) as well as two motifs (CCGARGS and CDTCNTC) to inhibit the expression of its target genes. Further analysis of ZmCLA4 target genes indicated that ZmCLA4 functions as a hub of multiple plant hormone signaling pathways because ZmCLA4 was found to directly bind to the promoters of multiple genes including ZmARF22 and ZmIAA26 in the auxin transport pathway, ZmBZR3 in the brassinosteroid signaling pathway, two ZmWRKY genes involved in abscisic acid metabolism, ZmCYP genes (ZmCYP75B1, ZmCYP93D1) related to jasmonic acid metabolism, and ZmABI3 involved in the ethylene response pathway. Overall, our work provides deep insights into the regulatory network of ZmCLA4 in controlling LA in maize.
PMID: 33270106
J Exp Bot , IF:5.908 , 2020 Dec doi: 10.1093/jxb/eraa501
Auxin biosynthesis and cellular efflux act together to regulate leaf vein patterning.
Institute of Biology II, Faculty of Biology, Albert-Ludwigs-University of Freiburg, Schanzlestrasse, Freiburg, Germany.; Physics of Biological Organization, Max Planck Institute for Dynamics and Self-Organization, Am Fassberg, Gottingen, Germany.; Institute of General Electrical Engineering, University of Rostock, Albert-Einstein-Str, Rostock, Germany.; Department of Botany, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto, Japan.; BIOSS Center for Biological Signalling Studies, Albert-Ludwigs-University of Freiburg, Schanzlestrasse, Freiburg, Germany.; Center for Biological Systems Analysis, Albert-Ludwigs-University of Freiburg, Habsburgerstrasse, Freiburg, Germany.; Freiburg Institute for Advanced Sciences (FRIAS), Albert-Ludwigs-University of Freiburg, Albertstrasse, Freiburg, Germany.; Department of Physics and Astronomy, University of Pennsylvania, PA, USA.
Our current understanding of vein development in leaves is based on canalization of the plant hormone auxin into self-reinforcing streams which determine the sites of vascular cell differentiation. By comparison, how auxin biosynthesis affects leaf vein patterning is less well understood. Here, after observing that inhibiting polar auxin transport rescues the sparse leaf vein phenotype in auxin biosynthesis mutants, we propose that the processes of auxin biosynthesis and cellular auxin efflux work in concert during vein development. By using computational modelling, we show that localized auxin maxima are able to interact with mechanical forces generated by the morphological constraints which are imposed by during early primordium development. This interaction is able to explain four fundamental characteristics of midvein morphology in a growing leaf: i) distal cell division, ii) coordinated cell elongation, iii) a midvein positioned in the centre of the primordium, and iv) a midvein which is distally branched. Domains of auxin biosynthetic enzyme expression are not positioned by auxin canalization, as they are observed before auxin efflux proteins polarize. This suggests that the site-specific accumulation of auxin, as regulated by the balanced action of cellular auxin efflux and local auxin biosynthesis, is crucial for leaf vein formation.
PMID: 33263754
Development , IF:5.611 , 2020 Dec , V147 (24) doi: 10.1242/dev.196618
Asynchrony of ovule primordia initiation in Arabidopsis.
Joint International Research Laboratory of Metabolic & Developmental Sciences, School of Life Sciences & Biotechnology, Joint Center for Single Cell Biology, Shanghai Jiao Tong University, Shanghai 200240, China.; Faculty of Mechanical Engineering and Mechanics, Ningbo University, Ningbo, Zhejiang 315211, China.; State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, and National Center for Plant Gene Research, Beijing 100101, China.; College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China.; National Key Laboratory of Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences, Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, Shanghai 200032, China.; Joint International Research Laboratory of Metabolic & Developmental Sciences, School of Life Sciences & Biotechnology, Joint Center for Single Cell Biology, Shanghai Jiao Tong University, Shanghai 200240, China whlin@sjtu.edu.cn.
Plant ovule initiation determines the maximum of ovule number and has a great impact on the seed number per fruit. The detailed processes of ovule initiation have not been accurately described, although two connected processes, gynoecium and ovule development, have been investigated. Here, we report that ovules initiate asynchronously. The first group of ovule primordia grows out, the placenta elongates, the boundaries of existing ovules enlarge and a new group of primordia initiates from the boundaries. The expression pattern of different marker genes during ovule development illustrates that this asynchronicity continues throughout whole ovule development. PIN-FORMED1 polar distribution and auxin response maxima correlate with ovule primordia asynchronous initiation. We have established computational modeling to show how auxin dynamics influence ovule primordia initiation. Brassinosteroid signaling positively regulates ovule number by promoting placentae size and ovule primordia initiation through strengthening auxin response. Transcriptomic analysis demonstrates numerous known regulators of ovule development and hormone signaling, and many new genes are identified that are involved in ovule development. Taken together, our results illustrate that the ovule primordia initiate asynchronously and the hormone signals are involved in the asynchrony.
PMID: 33234714
Development , IF:5.611 , 2020 Dec , V147 (24) doi: 10.1242/dev.192625
HY5 and phytochrome activity modulate shoot-to-root coordination during thermomorphogenesis in Arabidopsis.
Plant Biology Laboratory, Salk Institute for Biological Studies, 10010 N Torrey Pines Rd, La Jolla, CA 92037, USA.; Howard Hughes Medical Institute, Salk Institute for Biological Studies, La Jolla, CA 92037, USA.; Umea Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, SE-901 83 Umea, Sweden.; Department of Biosciences, College of Life and Environmental Sciences, Stocker Road, Exeter EX4 4QD, UK.; Plant Biology Laboratory, Salk Institute for Biological Studies, 10010 N Torrey Pines Rd, La Jolla, CA 92037, USA wbusch@salk.edu.; Integrative Biology Laboratory, Salk Institute for Biological Studies, 10010 N Torrey Pines Rd, La Jolla, CA 92037, USA.
Temperature is one of the most impactful environmental factors to which plants adjust their growth and development. Although the regulation of temperature signaling has been extensively investigated for the aerial part of plants, much less is known and understood about how roots sense and modulate their growth in response to fluctuating temperatures. Here, we found that shoot and root growth responses to high ambient temperature are coordinated during early seedling development in Arabidopsis A shoot signaling module that includes HY5, the phytochromes and the PIFs exerts a central function in coupling these growth responses and maintaining auxin levels in the root. In addition to the HY5/PIF-dependent shoot module, a regulatory axis composed of auxin biosynthesis and auxin perception factors controls root responses to high ambient temperature. Taken together, our findings show that shoot and root developmental responses to temperature are tightly coupled during thermomorphogenesis and suggest that roots integrate energy signals with local hormonal inputs.
PMID: 33144393
J Integr Plant Biol , IF:4.885 , 2020 Dec doi: 10.1111/jipb.13043
AtNSF regulates leaf serration by modulating intracellular trafficking of PIN1 in Arabidopsis thaliana.
State Key Laboratory of Crop Biology, College of Life Sciences, Shandong Agricultural University, Daizong Street 61, Tai'an, 271018, China.; Sino-German Joint Research Center on Agricultural Biology, College of Life Sciences, Shandong Agricultural University, Daizong Street 61, Tai'an, 271018, China.; Institute of Biology II/Molecular Plant Physiology, Faculty of Biology, Albert-Ludwigs-University of Freiburg, Schanzlestrasse 1, D-79104, Freiburg, Germany.; Key Laboratory of Saline-alkali Vegetation Ecology Restoration, Ministry of Education, Alkali Soil Natural Environmental Science Center, Northeast Forestry University, Harbin, 150040, China.; BIOSS Centre for Biological Signalling Studies, Albert-Ludwigs-University Freiburg, Signalhaus, Schanzlestr. 18, D-79104, Freiburg, Germany.; Center for Biological Systems Analysis (ZBSA), Albert-Ludwigs-University Freiburg, Habsburger Str. 49, D-79104, Freiburg, Germany.
In eukaryotes, N-ethylmaleimide-sensitive factor (NSF) is a conserved AAA+ ATPase and a key component of the membrane trafficking machinery that promotes the fusion of secretory vesicles with target membranes. Here, we demonstrate that the Arabidopsis thaliana genome contains a single copy of NSF, AtNSF, which plays an essential role in the regulation of leaf serration. The AtNSF knock-down mutant, atnsf-1, exhibited more serrations in the leaf margin. Moreover, polar localization of the PIN-FORMED1 (PIN1) auxin efflux transporter was diffuse around the margins of atnsf-1 leaves and root growth was inhibited in the atnsf-1 mutant. More PIN1-GFP accumulated in the intracellular compartments of atnsf-1 plants, suggesting that AtNSF is required for intracellular trafficking of PIN between the endosome and plasma membrane. Furthermore, the serration phenotype was suppressed in the atnsf-1 pin1-8 double mutant, suggesting that AtNSF is required for PIN1-mediated polar auxin transport to regulate leaf serration. The CUP-SHAPED COTYLEDON2 (CUC2) transcription factor gene is up-regulated in atnsf-1 plants and the cuc2-3 single mutant exhibits smooth leaf margins, demonstrating that AtNSF also functions in the CUC2 pathway. Our results reveal that AtNSF regulates the PIN1-generated auxin maxima with a CUC2-mediated feedback loop to control leaf serration. This article is protected by copyright. All rights reserved.
PMID: 33289329
Int J Mol Sci , IF:4.556 , 2020 Dec , V21 (24) doi: 10.3390/ijms21249624
Physiological, Biochemical, and Transcriptomic Responses of Neolamarckia cadamba to Aluminum Stress.
State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangdong Key Laboratory for Innovative Development and Utilization of Forest Plant Germplasm, College of Forestry and Landscape Architecture, South China Agricultural University, Guangzhou 510642, China.; Guangdong Key Laboratory for Innovative Development and Utilization of Forest Plant Germplasm, College of Forestry and Landscape Architectures, South China Agricultural University, Guangzhou 510642, China.; State Forestry and Grassland Administration Key Laboratory of Silviculture in downstream areas of the Yellow River, College of Forestry, Shandong Agriculture University, Taian 271018, Shandong, China.; Root Biology Center & College of Natural Resources and Environment, South China Agricultural University, Guangzhou 510642, China.; Guangdong Laboratory of Lingnan Modern Agriculture, Guangzhou 510642, China.
Aluminum is the most abundant metal of the Earth's crust accounting for 7% of its mass, and release of toxic Al(3+) in acid soils restricts plant growth. Neolamarckia cadamba, a fast-growing tree, only grows in tropical regions with acidic soils. In this study, N. cadamba was treated with high concentrations of aluminum under acidic condition (pH 4.5) to study its physiological, biochemical, and molecular response mechanisms against high aluminum stress. High aluminum concentration resulted in significant inhibition of root growth with time in N. cadamba. The concentration of Al(3+) ions in the root tip increased significantly and the distribution of absorbed Al(3+) was observed in the root tip after Al stress. Meanwhile, the concentration of Ca, Mg, Mn, and Fe was significantly decreased, but P concentration increased. Aluminum stress increased activities of antioxidant enzymes such as superoxide dismutase (SOD), catalase from micrococcus lysodeiktic (CAT), and peroxidase (POD) in the root tip, while the content of MDA was decreased. Transcriptome analysis showed 37,478 differential expression genes (DEGs) and 4096 GOs terms significantly associated with treatments. The expression of genes regulating aluminum transport and abscisic acid synthesis was significantly upregulated; however, the genes involved in auxin synthesis were downregulated. Of note, the transcripts of several key enzymes affecting lignin monomer synthesis in phenylalanine pathway were upregulated. Our results shed light on the physiological and molecular mechanisms of aluminum stress tolerance in N. cadamba.
PMID: 33348765
Int J Mol Sci , IF:4.556 , 2020 Dec , V21 (24) doi: 10.3390/ijms21249528
Overexpression of the Auxin Receptor AFB3 in Arabidopsis Results in Salt Stress Resistance and the Modulation of NAC4 and SZF1.
Departamento de Genetica Molecular y Microbiologia, Facultad de Ciencias Biologicas, Pontificia Universidad Catolica de Chile, Santiago 8331150, Chile.; Departamento de Fruticultura y Enologia, Facultad de Agronomia e Ingenieria Forestal, Pontificia Universidad Catolica de Chile, Santiago 8331150, Chile.; Laboratorio de Biotecnologia Celular, Facultad de Recursos Naturales Renovables, Universidad Arturo Prat, Iquique 1100000, Chile.
Soil salinity is a key problem for crop production worldwide. High salt concentration in soil negatively modulates plant growth and development. In roots, salinity affects the growth and development of both primary and lateral roots. The phytohormone auxin regulates various developmental processes during the plant's life cycle, including several aspects of root architecture. Auxin signaling involves the perception by specialized receptors which module several regulatory pathways. Despite their redundancy, previous studies have shown that their functions can also be context-specific depending on tissue, developmental or environmental cues. Here we show that the over-expression of Auxin Signaling F-Box 3 receptor results in an increased resistance to salinity in terms of root architecture and germination. We also studied possible downstream signaling components to further characterize the role of auxin in response to salt stress. We identify the transcription factor SZF1 as a key component in auxin-dependent salt stress response through the regulation of NAC4. These results give lights of an auxin-dependent mechanism that leads to the modulation of root system architecture in response to salt identifying a hormonal cascade important for stress response.
PMID: 33333760
Int J Mol Sci , IF:4.556 , 2020 Dec , V21 (24) doi: 10.3390/ijms21249506
Maize microRNA166 Inactivation Confers Plant Development and Abiotic Stress Resistance.
National Key Laboratory of Wheat and Maize Crop Science, Collaborative Innovation Center of Henan Grain Crops, College of Agronomy, Henan Agricultural University, Zhengzhou 450002, China.; Plant Molecular and Cellular Biology Program, University of Florida, Gainesville, FL 32611, USA.; Department of Biological Sciences and Biotechnology Research Center, Michigan Technological University, Houghton, MI 49931, USA.
MicroRNAs are important regulators in plant developmental processes and stress responses. In this study, we generated a series of maize STTM166 transgenic plants. Knock-down of miR166 resulted in various morphological changes, including rolled leaves, enhanced abiotic stress resistance, inferior yield-related traits, vascular pattern and epidermis structures, tassel architecture, as well as abscisic acid (ABA) level elevation and indole acetic acid (IAA) level reduction in maize. To profile miR166 regulated genes, we performed RNA-seq and qRT-PCR analysis. A total of 178 differentially expressed genes (DEGs) were identified, including 118 up-regulated and 60 down-regulated genes. These DEGs were strongly enriched in cell and intercellular components, cell membrane system components, oxidoreductase activity, single organism metabolic process, carbohydrate metabolic process, and oxidation reduction process. These results indicated that miR166 plays important roles in auxin and ABA interaction in monocots, yet the specific mechanism may differ from dicots. The enhanced abiotic stress resistance is partly caused via rolling leaves, high ABA content, modulated vascular structure, and the potential changes of cell membrane structure. The inferior yield-related traits and late flowering are partly controlled by the decreased IAA content, the interplay of miR166 with other miRNAs and AGOs. Taken together, the present study uncovered novel functions of miR166 in maize, and provide insights on applying short tandem target mimics (STTM) technology in plant breeding.
PMID: 33327508
Int J Mol Sci , IF:4.556 , 2020 Dec , V21 (24) doi: 10.3390/ijms21249437
Protein Levels of Several Arabidopsis Auxin Response Factors Are Regulated by Multiple Factors and ABA Promotes ARF6 Protein Ubiquitination.
State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresouces, College of Life Sciences, South China Agricultural University, Guangzhou 510642, China.; Department of Biochemistry, Microbiology and Immunology, University of Saskatchewan, Saskatoon, SK S7N 5E5, Canada.
The auxin response factor (ARF) transcription factors are a key component in auxin signaling and play diverse functions in plant growth, development, and stress response. ARFs are regulated at the transcript level and posttranslationally by protein modifications. However, relatively little is known regarding the control of ARF protein levels. We expressed five different ARFs with an HA (hemagglutinin) tag and observed that their protein levels under the same promoter varied considerably. Interestingly, their protein levels were affected by several hormonal and environmental conditions, but not by the auxin treatment. ABA (abscisic acid) as well as 4 degrees C and salt treatments decreased the levels of HA-ARF5, HA-ARF6, and HA-ARF10, but not that of HA-ARF19, while 37 degrees C treatment increased the levels of the four HA-ARFs, suggesting that the ARF protein levels are regulated by multiple factors. Furthermore, MG132 inhibited the reduction of HA-ARF6 level by ABA and 4 degrees C treatments, suggesting that these treatments decrease HA-ARF6 level through 26S proteasome-mediated protein degradation. It was also found that ABA treatment drastically increased HA-ARF6 ubiquitination, without strongly affecting the ubiquitination profile of the total proteins. Together, these results reveal another layer of control on ARFs, which could serve to integrate multiple hormonal and environmental signals into the ARF-regulated gene expression.
PMID: 33322385
Front Plant Sci , IF:4.402 , 2020 , V11 : P590985 doi: 10.3389/fpls.2020.590985
Reaction Wood Anatomical Traits and Hormonal Profiles in Poplar Bent Stem and Root.
Department of Biosciences and Territory, University of Molise, Pesche, Italy.; Department of Biotechnology and Life Science, University of Insubria, Varese, Italy.; Umea Plant Science Centre, Department of Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, Umea, Sweden.; Laboratory of Growth Regulators, Institute of Experimental Botany of the Czech Academy of Sciences and Faculty of Science of Palacky University, Olomouc, Czechia.; Department of Chemistry and Biology 'A. Zambelli', University of Salerno, Fisciano, Italy.
Reaction wood (RW) formation is an innate physiological response of woody plants to counteract mechanical constraints in nature, reinforce structure and redirect growth toward the vertical direction. Differences and/or similarities between stem and root response to mechanical constraints remain almost unknown especially in relation to phytohormones distribution and RW characteristics. Thus, Populus nigra stem and root subjected to static non-destructive mid-term bending treatment were analyzed. The distribution of tension and compression forces was firstly modeled along the main bent stem and root axis; then, anatomical features, chemical composition, and a complete auxin and cytokinin metabolite profiles of the stretched convex and compressed concave side of three different bent stem and root sectors were analyzed. The results showed that in bent stems RW was produced on the upper stretched convex side whereas in bent roots it was produced on the lower compressed concave side. Anatomical features and chemical analysis showed that bent stem RW was characterized by a low number of vessel, poor lignification, and high carbohydrate, and thus gelatinous layer in fiber cell wall. Conversely, in bent root, RW was characterized by high vessel number and area, without any significant variation in carbohydrate and lignin content. An antagonistic interaction of auxins and different cytokinin forms/conjugates seems to regulate critical aspects of RW formation/development in stem and root to facilitate upward/downward organ bending. The observed differences between the response stem and root to bending highlight how hormonal signaling is highly organ-dependent.
PMID: 33363556
Front Plant Sci , IF:4.402 , 2020 , V11 : P577235 doi: 10.3389/fpls.2020.577235
Difference Between Day and Night Temperatures Affects Stem Elongation in Tomato (Solanum lycopersicum) Seedlings via Regulation of Gibberellin and Auxin Synthesis.
RIKEN Center for Sustainable Resource Science, Yokohama, Japan.; Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan.; Department of Chemical and Biological Sciences, Faculty of Science, Japan Women's University, Tokyo, Japan.; Department of International Environmental and Agricultural Science, Tokyo University of Agriculture and Technology, Tokyo, Japan.; NARO, Institute of Vegetable and Floriculture Science, Tsu, Japan.; Department of Biochemistry, Okayama University of Science, Okayama, Japan.
Temperature is a critical environmental factor governing plant growth and development. The difference between day temperature (DT) and night temperature (NT), abbreviated as DIF, influences plant architecture. Subjecting plants to artificial DIF treatments is an effective strategy in ornamental horticulture. For example, negative DIF (when DT - NT < 0) generally inhibits stem elongation, resulting in dwarf plants. However, the mechanisms underlying stem growth regulation by DIF remains to be completely elucidated. In this study, we aimed to analyze the growth, transcriptome, and phytohormone profiles of tomato (Solanum lycopersicum) seedlings grown under different DIF treatments. Under positive DIF (when DT - NT > 0), in contrast to the control temperature (25 degrees C/20 degrees C, DT/NT), high temperature (30 degrees C/25 degrees C) increased stem length and thickness, as well as the number of xylem vessels. Conversely, compared with the positive high temperature DIF treatment (30 degrees C/25 degrees C), under negative DIF treatment (25 degrees C/30 degrees C) stem elongation was inhibited, but stem thickness and the number of xylem vessels were not affected. The negative DIF treatment decreased the expression of gibberellin (GA)-, auxin-, and cell wall-related genes in the epicotyl, as well as the concentrations of GAs and indole-3-acetic acid (IAA). The expression of these genes and concentrations of these hormones increased under high temperature compared to those under the control temperature positive DIF. Our results suggest that stem length in tomato seedlings is controlled by changes in GA and IAA biosynthesis in response to varying day and night temperatures.
PMID: 33363551
Front Plant Sci , IF:4.402 , 2020 , V11 : P602680 doi: 10.3389/fpls.2020.602680
Targeted Transgene Expression in Rice Using a Callus Strong Promoter for Selectable Marker Gene Control.
State Key Laboratory for Managing Biotic and Chemical Threats to the Quality and Safety of Agro-Products, Ministry of Agriculture Key Laboratory for Plant Protection and Biotechnology, Zhejiang Provincial Key Laboratory of Plant Virology, Zhejiang Academy of Agricultural Sciences, Hangzhou, China.; College of Plant Protection, Northwest A&F University, Yangling, China.; College of Chemistry and Life Sciences, Zhejiang Normal University, Jinhua, China.; Institute of Plant Virology, Ningbo University, Ningbo, China.; Institute of Biotechnology, Ningbo Academy of Agricultural Sciences, Ningbo, China.
Precise expression of a transgene in the desired manner is important for plant genetic engineering and gene function deciphering, but it is a challenge to obtain specific transgene expression free from the interference of the constitutive promoters used to express the selectable marker gene, such as the Cauliflower mosaic virus (CaMV) 35S promoter. So, the solutions to avoid these inappropriate regulations are largely demanded. In this study, we report the characterization of a callus strong promoter (CSP1) in rice and its application for accurate transgene expression. Our results indicate that the high expression of the CSP1 promoter in the callus enables efficient selection of hygromycin equivalent to that provided by the CaMV 35S promoter, whereas its expression in other tissues is low. To evaluate possible leaky effects, the expression of a beta-glucuronidase reporter driven by six specific promoters involving hormone signaling, pathogen response, cell fate determination, and proliferation was observed in transgenic rice plants generated by CSP1-mediated selection. Distinct beta-glucuronidase expression was found consistently in most of the transgenic lines obtained for each promoter. In addition, we applied these specific marker lines to investigate the root cellular responses to exogenous cytokinin and auxin treatment. The results reveal that the root growth inhibition by cytokinin was differently regulated at high and low concentrations. In summary, we have established the feasibility of using callus-specific promoter-dependent selection to mitigate the transgene misexpression in rice. By enabling efficient transformation, rice plants with reliable transgene expression will be easily acquired for broad applications.
PMID: 33362834
Front Plant Sci , IF:4.402 , 2020 , V11 : P617162 doi: 10.3389/fpls.2020.617162
Updates on BES1/BZR1 Regulatory Networks Coordinating Plant Growth and Stress Responses.
Department of Genetics, Development and Cell Biology, Plant Sciences Institute, Iowa State University, Ames, IA, United States.
Brassinosteroids (BRs) play pivotal roles in the regulation of many dimensions of a plant's life. Hence, through extensive efforts from many research groups, BR signaling has emerged as one of the best-characterized plant signaling pathways. The key molecular players of BR signaling from the cell surface to the nucleus important for the regulation of plant growth and development are well-established. Recent data show that BRs also modulate plant responses to environmental stresses such as drought and pathogen infection. In this mini review, we present the recent progress in BR signaling specifically in the post-translational SUMO modification of BR's master regulators, BES1/BZR1. We also discuss recent findings on the crosstalk between BR, UV light, and jasmonic acid signaling pathways to balance growth during light stress and pathogen infections. Finally, we describe the current update on the molecular link between BR signaling and intracellular auxin transport that essential for plant development.
PMID: 33343611
Physiol Plant , IF:4.148 , 2020 Dec doi: 10.1111/ppl.13305
Adventitious root formation in crops-Potato as an example.
Department of Biological Sciences, Birla Institute of Technology and Science, Pilani, India.; Institute of Plant Sciences, Agricultural Research Organization, Volcani Center, Rishon LeZion, Israel.
The root system of potato is made up of adventitious roots (AR) that form at the base of a sprout once it emerges from the mother tuber. By definition, AR originate from dormant preformed meristems, or from cells neighboring vascular tissues in stems or leaves. This may occur as part of the developmental program of the plant (e.g., potato), or when replacing the embryonic primary roots in response to stress conditions, such as flooding, nutrient deprivation, or wounding. AR formation is studied mainly in cereals and model plants, and less is known about its developmental program in root and tuber crops. In this review, we summarize the recent data on AR development in potato and relate this knowledge to what is known from model plants. For example, AR formation following stem cutting in potato follows a pattern of initiation, expression, and emergence phases that are known for other plants and involves auxin, the master regulator of AR induction and development. Molecular regulation of AR formation and the effect of environmental stresses are discussed. Understanding the origin and nature of AR systems in important crops will contribute to increased production and improve global food security.
PMID: 33305392
Physiol Plant , IF:4.148 , 2020 Dec doi: 10.1111/ppl.13295
Transcriptional variation analysis of Arabidopsis ecotypes in response to drought and salt stresses dissects commonly regulated networks.
Key Laboratory of Horticultural Plant Biology, Ministry of Education, College of Horticulture and Forestry Sciences, Huazhong Agricultural University, Wuhan, China.
Salinity and drought conditions commonly result in osmotic and oxidative stresses, while salinity additionally causes ionic stress. In this study, we identified specific genes regulated by osmotic and ionic stresses in five Arabidopsis ecotypes. Shahdara (SHA) and C24 ecotypes were more tolerant to salt and drought stresses at the seedling growth stage, as evidenced by lower water loss rate, lower electrolyte leakage, and higher survival rate when compared to the other three ecotypes under drought and salinity conditions. Transcriptomic analysis revealed that 3700 and 2242 genes were differentially regulated by salt and osmotic stresses, respectively. Totally 78.1% of upregulated and 62.0% of downregulated genes by osmotic stress were also commonly regulated by salt stress. Gene ontology term enrichment analysis showed that auxin indole-3-acetic acid (IAA), abscisic acid, cytokinin, and gibberellic acid pathways were regulated by the osmotic stress, while IAA, jasmonic acid, and ethylene pathways were changed by the ionic stress. The nutrient and water uptake pathways were regulated by both the osmotic and ionic stresses, whereas ion transportation and kinase pathways were modulated by the ionic stress. Additionally, we characterized bHLH61 as a negative regulator in response to salt and drought stresses. This study provided new clues of plant responses to salt and drought stresses.
PMID: 33280127
Plant Cell Physiol , IF:4.062 , 2020 Dec doi: 10.1093/pcp/pcaa150
Cadmium inhibits lateral root emergence in rice by disrupting OsPIN-mediated auxin distribution and the protective effect of OsHMA3.
State Key Laboratory of Crop Genetics and Germplasm Enhancement, College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, China.; State Key Laboratory of Plant Physiology and Biochemistry, College of Life Science, Zhejiang University, Hangzhou, China.
Cadmium (Cd) strongly inhibits root growth, especially the formation of lateral roots (LRs). The mechanism of Cd inhibition on LR formation in rice (Oryza sativa) remains unclear. In this study, we found that LR emergence in rice was inhibited significantly by 1 microM Cd and almost completely arrested by 5 microM Cd. Cadmium suppressed both the formation and subsequent development of the lateral root primordium (LRP). By using transgenic rice expressing the auxin response reporters DR5::GUS and DR5rev::VENUS, we found that Cd markedly reduced the auxin levels in the stele and LRP. Cadmium rapidly downregulated the expression of the auxin efflux transporter genes OsPIN1b, OsPIN1c and OsPIN9 in the stele and LPR. The emergence of LRs in a rice cultivar with a null allele of OsHMA3 (Heavy Metal ATPase 3) was more sensitive to Cd than cultivars with functional alleles. Overexpression of functional OsHMA3 in rice greatly alleviated the inhibitory effect of Cd, but the protective effect of OsHMA3 was abolished by the auxin polar transport inhibitor 1-N-naphthylphthalamic acid. The results suggest that Cd inhibits LR development in rice by disrupting OsPIN-mediated auxin distribution to LPR and OsHMA3 protects against Cd toxicity by sequestering Cd into the vacuoles.
PMID: 33300991
Sci Rep , IF:3.998 , 2020 Dec , V10 (1) : P21294 doi: 10.1038/s41598-020-78027-5
Transcriptome analysis reveals that exogenous ethylene activates immune and defense responses in a high late blight resistant potato genotype.
Institute of Vegetables and Flowers, Shandong Academy of Agricultural Sciences, Molecular Biology Key Laboratory of Shandong Facility Vegetable, National Vegetable Improvement Center Shandong Sub-Center, Huang-Huai-Hai Region Scientific Observation and Experimental Station of Vegetables, Ministry of Agriculture and Rural Affairs, Jinan, 250100, China.; Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Key Laboratory of Biology and Genetic Improvement of Tuber and Root Crop, Ministry of Agriculture and Rural Affairs, Beijing, 100081, China.; Institute of Vegetables and Flowers, Shandong Academy of Agricultural Sciences, Molecular Biology Key Laboratory of Shandong Facility Vegetable, National Vegetable Improvement Center Shandong Sub-Center, Huang-Huai-Hai Region Scientific Observation and Experimental Station of Vegetables, Ministry of Agriculture and Rural Affairs, Jinan, 250100, China. feng-dd@126.com.; Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Key Laboratory of Biology and Genetic Improvement of Tuber and Root Crop, Ministry of Agriculture and Rural Affairs, Beijing, 100081, China. liguangcun@caas.cn.
Ethylene (ET) is one of the many important signaling hormones that functions in regulating defense responses in plants. Gene expression profiling was conducted under exogenous ET application in the high late blight resistant potato genotype SD20 and the specific transcriptional responses to exogenous ET in SD20 were revealed. Analysis of differentially expressed genes (DEGs) generated a total of 1226 ET-specific DEGs, among which transcription factors, kinases, defense enzymes and disease resistance-related genes were significantly differentially expressed. GO enrichment and KEGG metabolic pathway analysis also revealed that numerous defense regulation-related genes and defense pathways were significantly enriched. These results were consistent with the interaction of SD20 and Phytophthora infestans in our previous study, indicating that exogenous ET stimulated the defense response and initiated a similar defense pathway compared to pathogen infection in SD20. Moreover, multiple signaling pathways including ET, salicylic acid, jasmonic acid, abscisic acid, auxin, cytokinin and gibberellin were involved in the response to exogenous ET, which indicates that many plant hormones work together to form a complex network to resist external stimuli in SD20. ET-induced gene expression profiling provides insights into the ET signaling transduction pathway and its potential mechanisms in disease defense systems in potato.
PMID: 33277549
Biochem Biophys Res Commun , IF:2.985 , 2020 Dec , V533 (4) : P717-722 doi: 10.1016/j.bbrc.2020.09.065
Auxin regulates anthocyanin biosynthesis through the auxin repressor protein MdIAA26.
National Key Laboratory of Crop Biology, Shandong Collaborative Innovation Center of Fruit & Vegetable Quality and Efficient Production, College of Horticulture Science and Engineering, Shandong Agricultural University, Tai'an, Shandong, 271018, China.; State Key Laboratory of Crop Stress Biology for Arid Areas, College of Plant Protection, Northwest A&F University, Yangling, 712100, Shaanxi, China.; National Key Laboratory of Crop Biology, Shandong Collaborative Innovation Center of Fruit & Vegetable Quality and Efficient Production, College of Horticulture Science and Engineering, Shandong Agricultural University, Tai'an, Shandong, 271018, China. Electronic address: fap_296566@163.com.; National Key Laboratory of Crop Biology, Shandong Collaborative Innovation Center of Fruit & Vegetable Quality and Efficient Production, College of Horticulture Science and Engineering, Shandong Agricultural University, Tai'an, Shandong, 271018, China. Electronic address: haoyujin@sdau.edu.cn.
Auxin plays an important role in plant growth and development; for example, it regulates the elongation and division of plant cells, the formation of plantlet's geotropism and phototropism, and the growth of main lateral roots and hypocotyl. IAA gene is associated with auxin and can response to biotic and abiotic stress in plants. However, the regulatory effect of auxin on anthocyanin accumulation has been rarely reported. In this study, we show that auxin inhibites the accumulation of anthocyanin and decreases the expression of genes related to anthocyanin synthesis in calli, leaves, and seedlings of apple. The expression levels of MdIAA family genes were determined, and we found that MdIAA26 significantly responded to auxin, which also induced MdIAA26 degradation. Functional analysis of MdIAA26 showed that overexpressing MdIAA26 in apple calli and Arabidopsis could promote the accumulation of anthocyanin and up-regulate the genes related to anthocyanin synthesis. Furthermore, the MdIAA26-overexpressing Arabidopsis could counteract auxin-induced inhibition on anthocyanin accumulation, which indicates that auxin inhibits the accumulation of anthocyanin in apple by degrading MdIAA26 protein.
PMID: 32981681
Gene , IF:2.984 , 2020 Dec : P145355 doi: 10.1016/j.gene.2020.145355
Transcriptome sequencing and differential gene expression analysis reveal the mechanisms involved in seed germination and protocorm development of Calanthe tsoongiana.
Research Institution of Subtropical Forestry, Chinese Academy of Forestry, Hangzhou 311400, Zhejiang, China.; Research Institution of Subtropical Forestry, Chinese Academy of Forestry, Hangzhou 311400, Zhejiang, China. Electronic address: tmin115@126.com.
Calanthe tsoongiana is a rare orchid species native to China. Asymbiotic seed germination is of great importance in the ex situ conservation of this species. Based on morphological characteristics and anatomical structures, the C. tsoongiana developmental process from seeds to seedlings was divided into four stages (SA, PB, PC and PD), and subsequently, changes in endogenous hormone contents and gene expression were assessed using RNA-seq analysis. K-means analysis divided the DEGs into eight clusters. The gene expression decreased markedly between the imbibed seed and globular protocorm stages, with this being the most notably enriched cluster. During the seed germination period, DEGs were dominated by ATP metabolic processes, respiration and photosynthesis. A small change in gene expression was found in the globular protocorm versus the finger-like protocorm stages. During the last developmental stage, DEGs were significantly enriched in lignin catabolic processes and plant-type secondary cell wall biogenesis. DEG homologs, such as TSA1, DAO, NCED1, STM, and CUC2, were related to phytohormones and the morphogenesis of shoots, leaves and roots. Particularly, interactions between CUC2 and STM as well as AS1 and STM were likely involved in protocorm formation and development. Furthermore, TSA1 and DAO were distinctly validated and implicated in the synthesis and metabolism of auxin, which has a pivotal role in plant development. Our study is the first to combine morphological and transcriptome analysis to examine the process of protocorm formation and development. The results provide a foundation for understanding the mechanisms of seed germination and protocorm development of C. tsoongiana.
PMID: 33340562
Gene , IF:2.984 , 2020 Dec : P145349 doi: 10.1016/j.gene.2020.145349
Genome-wide identification of polar auxin transporter gene families reveals a possible new polar auxin flow in inverted cuttings of Populus yunnanensis.
Key Laboratory for Forest Genetic and Tree Improvement and Propagation in Universities of Yunnan Province, Southwest Forestry University, Kunming 650224, China; Institute of Jiangxi Oil-tea Camellia, Jiujiang University, Jiujiang 332005, China. Electronic address: 6090078@jju.edu.cn.; Key Laboratory for Forest Genetic and Tree Improvement and Propagation in Universities of Yunnan Province, Southwest Forestry University, Kunming 650224, China; Key Laboratory of Biodiversity Conservation in Southwest China, State Forestry Administration, Southwest Forestry University, Kunming 650224, China. Electronic address: zhongyuanyuan221@sina.com.; Key Laboratory for Forest Genetic and Tree Improvement and Propagation in Universities of Yunnan Province, Southwest Forestry University, Kunming 650224, China; Key Laboratory of Biodiversity Conservation in Southwest China, State Forestry Administration, Southwest Forestry University, Kunming 650224, China. Electronic address: lisiqi771@163.com.; Key Laboratory for Forest Genetic and Tree Improvement and Propagation in Universities of Yunnan Province, Southwest Forestry University, Kunming 650224, China; Key Laboratory of Biodiversity Conservation in Southwest China, State Forestry Administration, Southwest Forestry University, Kunming 650224, China. Electronic address: feixuan0101@163.com.; Key Laboratory for Forest Genetic and Tree Improvement and Propagation in Universities of Yunnan Province, Southwest Forestry University, Kunming 650224, China; Key Laboratory of Biodiversity Conservation in Southwest China, State Forestry Administration, Southwest Forestry University, Kunming 650224, China. Electronic address: ganpeihua33@sina.cn.; Key Laboratory for Forest Genetic and Tree Improvement and Propagation in Universities of Yunnan Province, Southwest Forestry University, Kunming 650224, China; Key Laboratory of Biodiversity Conservation in Southwest China, State Forestry Administration, Southwest Forestry University, Kunming 650224, China. Electronic address: zdkathy@163.com.; Key Laboratory for Forest Genetic and Tree Improvement and Propagation in Universities of Yunnan Province, Southwest Forestry University, Kunming 650224, China; Key Laboratory of Biodiversity Conservation in Southwest China, State Forestry Administration, Southwest Forestry University, Kunming 650224, China; Key Laboratory for Forest Resources Conservation and Utilization in the Southwest Mountains of China, Ministry of Education, Southwest Forestry University, Kunming 650224, China. Electronic address: hecz@swfu.edu.cn.
Inverted cuttings of Populus yunnanensis are characterized by enlarged stems and dwarfed new shoots, and phytohormones play a crucial role in the response to inversion. The polar auxin transport (PAT) system is distinct from the transport systems of other hormones and is controlled by three major transporter gene families: pin-formed (PIN), auxin-resistant/like aux (AUX/LAX) and ATP-binding cassette transporters of the B class (ABCB). Here, we identified these three families in P. trichocarpa, P. euphratica and P. yunnanensis through a genome-wide analysis. The Populus PIN, AUX/LAX and ABCB gene families comprised 15, 8 and 31 members, respectively. Most PAT genes in Populus and Arabidopsis were identified as clear sister pairs, and some had unique motifs. Transcriptome profiling revealed that the expression of most PAT genes was unrelated to cutting inversion and that only several genes showed altered expression when cuttings were inverted. The auxin content difference at positions was opposite in upright and inverted cutting bodies during rooting, which obeyed the original plant polarity. However, during plant growth, the two direction types exhibited similar auxin movements in the cutting bodies, and the opposite auxin changes were observed in new shoots. Four PAT genes with a positive response to cutting inversion, PyuPIN10, PyuPIN11, PyuLAX6 and PyuABCB27, showed diverse expression patterns between upright and inverted cuttings during rooting and plant growth. Furthermore, PAT gene expression retained its polarity, which differs from the results found for auxin flow during plant growth. The inconformity indicated that a new downward auxin flow in addition to the old upward flow might be established during the growth of inverted cuttings. Some highly polar PAT genes were involved in the maintenance of original auxin polarity, which might cause the enlarged stems of inverted cuttings. This work lays a foundation for understanding the roles of auxin transport in plant responses to inversion.
PMID: 33338511
Biosci Rep , IF:2.942 , 2020 Dec , V40 (12) doi: 10.1042/BSR20202959
Investigating the reaction and substrate preference of indole-3-acetaldehyde dehydrogenase from the plant pathogen Pseudomonas syringae PtoDC3000.
Department of Biology, Washington University in St. Louis, St. Louis, MO 63130, U.S.A.; Department of Biology, Williams College, Williamstown, MA 01267, U.S.A.; Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637, U.S.A.; Department of Chemistry and Biochemistry, University of North Carolina Wilmington, Wilmington, NC 28403, U.S.A.
Aldehyde dehydrogenases (ALDHs) catalyze the conversion of various aliphatic and aromatic aldehydes into corresponding carboxylic acids. Traditionally considered as housekeeping enzymes, new biochemical roles are being identified for members of ALDH family. Recent work showed that AldA from the plant pathogen Pseudomonas syringae strain PtoDC3000 (PtoDC3000) functions as an indole-3-acetaldehyde dehydrogenase for the synthesis of indole-3-acetic acid (IAA). IAA produced by AldA allows the pathogen to suppress salicylic acid-mediated defenses in the model plant Arabidopsis thaliana. Here we present a biochemical and structural analysis of the AldA indole-3-acetaldehyde dehydrogenase from PtoDC3000. Site-directed mutants targeting the catalytic residues Cys302 and Glu267 resulted in a loss of enzymatic activity. The X-ray crystal structure of the catalytically inactive AldA C302A mutant in complex with IAA and NAD+ showed the cofactor adopting a conformation that differs from the previously reported structure of AldA. These structures suggest that NAD+ undergoes a conformational change during the AldA reaction mechanism similar to that reported for human ALDH. Site-directed mutagenesis of the IAA binding site indicates that changes in the active site surface reduces AldA activity; however, substitution of Phe169 with a tryptophan altered the substrate selectivity of the mutant to prefer octanal. The present study highlights the inherent biochemical versatility of members of the ALDH enzyme superfamily in P. syringae.
PMID: 33325526
Plants (Basel) , IF:2.762 , 2020 Dec , V9 (12) doi: 10.3390/plants9121722
Effects of Phosphate Shortage on Root Growth and Hormone Content of Barley Depend on Capacity of the Roots to Accumulate ABA.
Ufa Institute of Biology of Ufa Federal Research Centre of the Russian Academy of Sciences, Pr. Octyabrya, 69, 450054 Ufa, Russia.; The Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ, UK.; Institute of Biochemistry and Genetics of Ufa Federal Research Centre of Russian Academy of Sciences, Pr. Octyabrya, 71, 450054 Ufa, Russia.; Department of Biology, Bashkir State University, Zaki-Validi St. 32, 450074 Ufa, Russia.
Although changes in root architecture in response to the environment can optimize mineral and water nutrient uptake, mechanisms regulating these changes are not well-understood. We investigated whether P deprivation effects on root development are mediated by abscisic acid (ABA) and its interactions with other hormones. The ABA-deficient barley mutant Az34 and its wild-type (WT) were grown in P-deprived and P-replete conditions, and hormones were measured in whole roots and root tips. Although P deprivation decreased growth in shoot mass similarly in both genotypes, only the WT increased primary root length and number of lateral roots. The effect was accompanied by ABA accumulation in root tips, a response not seen in Az34. Increased ABA in P-deprived WT was accompanied by decreased concentrations of cytokinin, an inhibitor of root extension. Furthermore, P-deficiency in the WT increased auxin concentration in whole root systems in association with increased root branching. In the ABA-deficient mutant, P-starvation failed to stimulate root elongation or promote branching, and there was no decline in cytokinin and no increase in auxin. The results demonstrate ABA's ability to mediate in root growth responses to P starvation in barley, an effect linked to its effects on cytokinin and auxin concentrations.
PMID: 33297400
PeerJ , IF:2.379 , 2020 , V8 : Pe10492 doi: 10.7717/peerj.10492
Effects of auxin (indole-3-butyric acid) on growth characteristics, lignification, and expression profiles of genes involved in lignin biosynthesis in carrot taproot.
State Key Laboratory of Crop Genetics and Germplasm Enhancement, Ministry of Agriculture and Rural Affairs Key Laboratory of Biology and Germplasm Enhancement of Horticultural Crops in East China, College of Horticulture, Nanjing Agricultural University, Nanjing, China.; Department of Horticulture, Faculty of Agriculture, Damanhour University, Damanhour, Egypt.; School of Life Science and Food Engineering, Huaiyin Institute of Technology, Huaian, China.
Carrot is an important root vegetable crop abundant in bioactive compounds including carotenoids, vitamins, and dietary fibers. Carrot intake and its products are gradually growing owing to its high antioxidant activity. Auxins are a class of plant hormones that control many processes of plant growth and development. Yet, the effects of exogenous application of auxin on lignin biosynthesis and gene expression profiles of lignin-related genes in carrot taproot are still unclear. In order to investigate the effect of exogenous indole-3-butyric acid (IBA) on lignin-related gene profiles, lignin accumulation, anatomical structures and morphological characteristics in carrot taproots, carrots were treated with different concentrations of IBA (0, 50, 100, and 150 microM). The results showed that IBA application significantly improved the growth parameters of carrot. The 100 or 150 microM IBA treatment increased the number and area of xylem vessels, whereas transcript levels of lignin-related genes were restricted, resulting in a decline in lignin content in carrot taproots. The results indicate that taproot development and lignin accumulation may be influenced by the auxin levels within carrot plants.
PMID: 33354430