Mol Plant , IF:12.084 , 2021 Mar doi: 10.1016/j.molp.2021.03.011
A crosstalk between auxin and brassinosteroid regulates leaf shape by modulating growth anisotropy.
State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, The Innovative Academy of Seed Design, Chinese Academy of Sciences, Beijing 100101, China; College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China.; State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, The Innovative Academy of Seed Design, Chinese Academy of Sciences, Beijing 100101, China.; Beijing International Center for Mathematical Research, Peking University, Beijing 100871, China.; Key Laboratory of Microgravity (National Microgravity Laboratory), Center of Biomechanics and Bioengineering, and Beijing Key Laboratory of Engineered Construction and Mechanobiology, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China; School of Engineering Science, University of Chinese Academy of Sciences, Beijing 100049, China.; Beijing International Center for Mathematical Research, Peking University, Beijing 100871, China. Electronic address: yljiao@genetics.ac.cn.; College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China. Electronic address: yljiao@genetics.ac.cn.; State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, The Innovative Academy of Seed Design, Chinese Academy of Sciences, Beijing 100101, China; College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China. Electronic address: yljiao@genetics.ac.cn.
Leaf shape is highly variable within and among plant species, ranging from slender to oval-shaped. This is largely determined by the proximodistal axis of growth. However, little is known about how proximal-distal growth is controlled to determine leaf shape. Here, we show that Arabidopsis leaf and sepal proximodistal growth is tuned by two phytohormones. Two class A AUXIN RESPONSE FACTORs (ARFs), ARF6 and ARF8, activate the transcription of DWARF4, which encodes a key brassinosteroid (BR) biosynthetic enzyme. At the cellular level, the phytohormones promote more directional cell expansion along the proximodistal axis, as well as final cell sizes. BRs promote the demethyl-esterification of cell wall pectins, leading to isotropic in-plane cell wall loosening. Notably, numerical simulation showed that isotropic cell wall loosening could lead to directional cell and organ growth along the proximodistal axis. Taken together, we show that auxin acts through BRs biosynthesis to determine cell wall mechanics and directional cell growth to generate leaves of variable roundness.
PMID: 33722761
Plant J , IF:6.141 , 2021 Mar doi: 10.1111/tpj.15217
CsLOB1 regulates susceptibility to citrus canker through promoting cell proliferation in citrus.
Citrus Research Institute, Chinese Academy of Agricultural Sciences/Southwest University, Chongqing, 400712, P. R. China.; Brazilian Biosciences National Laboratory (LNBio), Brazilian Center for Research in Energy and Materials (CNPEM), Campinas, SP, Brazil.
Citrus sinensis lateral organ boundary 1 (CsLOB1) was previously identified as a critical disease susceptibility gene for citrus bacterial canker, which is caused by Xanthomonas citri subsp. citri (Xcc). However, the molecular mechanisms of CsLOB1 in citrus response to Xcc are still elusive. Here, we constructed transgenic plants overexpressing and RNAi-silencing of CsLOB1 using the canker-disease susceptible 'wanjincheng' orange (C. sinensis Osbeck) as explants. CsLOB1-overexpressing plants exhibited dwarf phenotypes with smaller and thicker leaf, increased branches and adventitious buds clustered on stems. These phenotypes were followed by a process of pustule- and canker-like development that exhibited enhanced cell proliferation. Pectin depolymerization and expansin accumulation were enhanced by CsLOB1 overexpression, while cellulose and hemicellulose synthesis were increased by CsLOB1 silence. Whilst overexpression of CsLOB1 increased susceptibility, RNAi-silencing of CsLOB1 enhanced resistance to canker disease without impairing pathogen entry. Transcriptome analysis revealed that CsLOB1 positively regulated cell wall degradation and modification processes, cytokinin metabolism, and cell division. Additionally, 565 CsLOB1-targeted genes were identified in chromatin immunoprecipitation-sequencing (ChIP-seq) experiments. Motif discovery analysis revealed that the most highly overrepresented binding sites had a conserved 6-bp 'GCGGCG' consensus DNA motif. RNA-seq and ChIP-seq data suggested that CsLOB1 directly activates the expression of four genes involved in cell wall remodeling, and three genes that participate in cytokinin and brassinosteroid hormone pathways. Our findings indicate that CsLOB1 promotes cell proliferation by mechanisms depending on cell wall remodeling and phytohormone signaling, which may be critical to citrus canker development and bacterial growth in citrus.
PMID: 33754403
J Exp Bot , IF:5.908 , 2021 Mar , V72 (7) : P2463-2476 doi: 10.1093/jxb/eraa592
The APETALA2 transcription factor LsAP2 regulates seed shape in lettuce.
Beijing Key Laboratory of Growth and Developmental Regulation for Protected Vegetable Crops, Department of Vegetable Science, College of Horticulture, China Agricultural University, Beijing, China.
Seeds are major vehicles of propagation and dispersal in plants. A number of transcription factors, including APETALA2 (AP2), play crucial roles during the seed development process in various plant species. However, genes essential for seed development and the regulatory networks that operate during seed development remain unclear in lettuce. Here, we identified a lettuce AP2 (LsAP2) gene that was highly expressed during the early stages of seed development. LsAP2 knockout plants obtained by the CRISPR/Cas9 system were used to explore the biological function of LsAP2. Compared with the wild type, the seeds of Lsap2 mutant plants were longer and narrower, and developed an extended tip at the seed top. After further investigating the structural characteristics of the seeds of Lsap2 mutant plants, we proposed a new function of LsAP2 in seed dispersal. Moreover, we identified several interactors of LsAP2. Our results showed that LsAP2 directly interacted with the lettuce homolog of BREVIPEDICELLUS (LsBP) and promoted the expression of LsBP. Transcriptome analysis revealed that LsAP2 might also be involved in brassinosteroid biosynthesis and signaling pathways. Taken together, our data indicate that LsAP2 has a significant function in regulating seed shape in lettuce.
PMID: 33340036
J Integr Plant Biol , IF:4.885 , 2021 Mar doi: 10.1111/jipb.13093
Protein farnesylation negatively regulates brassinosteroid signaling via reducing BES1 stability in Arabidopsis thaliana.
Ministry of Education Key Laboratory of Cell Activities and Stress Adaptations, School of Life Sciences, Lanzhou University, Lanzhou, 730000, China.
Brassinosteroids (BRs) are a group of steroidal phytohormones, playing critical roles in almost all physiological aspects during the life span of a plant. In Arabidopsis, BRs are perceived at the cell surface, triggering a reversible phosphorylation-based signaling cascade that leads to the activation and nuclear accumulation of a family of transcription factors, represented by BES1 and BZR1. Protein farnesylation is a type of post-translational modification, functioning in many important cellular processes. Previous studies demonstrated a role of farnesylation in BR biosynthesis via regulating the ER localization of a key bassinolide (BL) biosynthetic enzyme BR6ox2. Whether such a process is also involved in BR signaling, however, is not understood. Here, we demonstrate that protein farnesylation is involved in mediating BR signaling in Arabidopsis. A loss-of-function mutant of ERA1, encoding a beta subunit of the protein farnesyl transferase holoenzyme, can alter the BL sensitivity of bak1-4 from a reduced to a hypersensitive level. era1 can partially rescue the BR defective phenotype of a heterozygous mutant of bin2-1, a gain-of-function mutant of BIN2 which encodes a negative regulator in the BR signaling. Our genetic and biochemical analyses revealed that ERA1 plays a significant role in regulating the protein stability of BES1. This article is protected by copyright. All rights reserved.
PMID: 33764637
Plant Cell Rep , IF:3.825 , 2021 Mar doi: 10.1007/s00299-021-02683-8
Phytohormone signaling and crosstalk in regulating drought stress response in plants.
DST-INSPIRE Faculty, Agriculture Biotechnology Department, National Agri-Food Biotechnology Institute, Sector 81, Sahibzada Ajit Singh Nagar, Mohali, 140308, Punjab, India. salvi.prafull@gmail.com.; National Institute of Plant Genome Research, New Delhi, India.; ICAR-National Institute for Plant Biotechnology, New Delhi, India.; DST-INSPIRE Faculty, Agriculture Biotechnology Department, National Agri-Food Biotechnology Institute, Sector 81, Sahibzada Ajit Singh Nagar, Mohali, 140308, Punjab, India.; Department of Biotechnology, Shree Ramkrishna Institute of Computer Education and Applied Sciences, Veer Narmad South Gujarat University, Surat, Gujarat, India.; Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad, Telangana, India.
Phytohormones are ubiquitously involved in plant biological processes and regulate cellular signaling pertaining to unheralded environmental cues, such as salinity, drought, extreme temperature and nutrient deprivation. The association of phytohormones to nearly all the fundamental biological processes epitomizes the phytohormone syndicate as a candidate target for consideration during engineering stress endurance in agronomically important crops. The drought stress response is essentially driven by phytohormones and their intricate network of crosstalk, which leads to transcriptional reprogramming. This review is focused on the pivotal role of phytohormones in water deficit responses, including their manipulation for mitigating the effect of the stressor. We have also discussed the inherent complexity of existing crosstalk accrued among them during the progression of drought stress, which instigates the tolerance response. Therefore, in this review, we have highlighted the role and regulatory aspects of various phytohormones, namely abscisic acid, auxin, gibberellic acid, cytokinin, brassinosteroid, jasmonic acid, salicylic acid, ethylene and strigolactone, with emphasis on drought stress tolerance.
PMID: 33751168
Tree Physiol , IF:3.655 , 2021 Mar , V41 (3) : P444-459 doi: 10.1093/treephys/tpaa164
HrCYP90B1 modulating brassinosteroid biosynthesis in sea buckthorn (Hippophae rhamnoides L.) against fruit fly (Rhagoletis batava obseuriosa Kol.) infection.
School of Life Science, Institute of Life Science and Green Development, Hebei University, Baoding 071002, China.; Hebei Research Center for Geoanalysis, Baoding 071051, China.; Desert Forest Experimental Center, Chinese Academy of Forestry, Dengkou 015200, China.
Sea buckthorn is an important ecological and economic tree species, and its berries have been severely damaged by sea buckthorn fruit fly, Rhagoletis batava obseuriosa Kol. (Diptera: Tephritidae) (RBO). Brassinosteroid (BR) is widely involved in stress tolerance of plant. However, limited knowledge exists regarding the molecular mechanisms underlying insect resistance. Here, we found that BR content was much higher in sea buckthorn fruits with RBO infection than non-infection, and the damage rates of fruit with BR treatment were significantly lower than that of non-treatment. It indicated that BR could enhance RBO resistance in sea buckthorn. Several BR biosynthesis-related HrCYPs genes (CYP85A1/85A2/90A1/90B1/90C1/90D1/92A6/724B/734A1) were obtained and identified based on transcriptome analysis, of which the most up-regulated gene in fruits was HrCYP90B1 under RBO and mechanical damage. Overexpression of HrCYP90B1 in Arabidopsis thaliana showed BR and salicylic acid (SA) content was significantly increased, and the substrate campesterol (CR) of HrCYP90B1 content decreased. Further studies revealed that silencing HrCYP90B1 by virus-induced gene silencing resulted in decrease of BR, SA and defense-related enzymes contents, and increase of CR content. Silencing HrCYP90B1 also caused suppression of SA and activation of jasmonic acid pathways, enabling enhanced RBO susceptibility and more damage of fruits. Taken together, we obtained evidence that HrCYP90B1 was a positive regulator in RBO resistance improvement in sea buckthorn, which will provide comprehensive insights into the tree defense system of sea buckthorn to pest infection.
PMID: 33238299
BMC Genomics , IF:3.594 , 2021 Mar , V22 (1) : P147 doi: 10.1186/s12864-021-07455-y
Early transcriptome changes induced by the Geminivirus C4 oncoprotein: setting the stage for oncogenesis.
Department of Plant Pathology, University of Georgia, Athens, GA, USA. deom@uga.edu.; Department of Plant Biology, University of Georgia, Athens, GA, USA.; Department of Plant Pathology, University of Georgia, Athens, GA, USA.
BACKGROUND: The Beet curly top virus C4 oncoprotein is a pathogenic determinant capable of inducing extensive developmental abnormalities. No studies to date have investigated how the transcriptional profiles differ between plants expressing or not expressing the C4 oncoprotein. RESULTS: We investigated early transcriptional changes in Arabidopsis associated with expression of the Beet curly top virus C4 protein that represent initial events in pathogenesis via a comparative transcriptional analysis of mRNAs and small RNAs. We identified 48 and 94 differentially expressed genes at 6- and 12-h post-induction versus control plants. These early time points were selected to focus on direct regulatory effects of C4 expression. Since previous evidence suggested that the C4 protein regulated the brassinosteroid (BR)-signaling pathway, differentially expressed genes could be divided into two groups: those responsive to alterations in the BR-signaling pathway and those uniquely responsive to C4. Early transcriptional changes that disrupted hormone homeostasis, 18 and 19 differentially expressed genes at both 6- and 12-hpi, respectively, were responsive to C4-induced regulation of the BR-signaling pathway. Other C4-induced differentially expressed genes appeared independent of the BR-signaling pathway at 12-hpi, including changes that could alter cell development (4 genes), cell wall homeostasis (5 genes), redox homeostasis (11 genes) and lipid transport (4 genes). Minimal effects were observed on expression of small RNAs. CONCLUSION: This work identifies initial events in genetic regulation induced by a geminivirus C4 oncoprotein. We provide evidence suggesting the C4 protein regulates multiple regulatory pathways and provides valuable insights into the role of the C4 protein in regulating initial events in pathogenesis.
PMID: 33653270
Plant Signal Behav , IF:1.671 , 2021 Mar , V16 (3) : P1855845 doi: 10.1080/15592324.2020.1855845
ShHTL7 requires functional brassinosteroid signaling to initiate GA-independent germination.
Department of Cell & Systems Biology, University of Toronto , Toronto, Canada.
In the model plant Arabidopsis thaliana, two mutually antagonistic hormones regulate germination: abscisic acid (ABA) which promotes dormancy and gibberellins (GA) which breaks dormancy. Mutants auxotrophic for or insensitive to GA do not germinate. However, changes in the signaling flux through other hormone pathways will permit GA-independent germination. These changes include increased brassinosteroid (BR) signaling and decreased ABA signaling. Recently, strigolactone (SL) was also shown to enable GA-independent germination, provided the seeds express the SL receptor ShHTL7 from the parasitic plant Striga hermonthica. Here we show that a mutation which reduces sensitivity to BR (bri1-6) prevents ShHTL7 from promoting GA-independent germination. Further, we show that neither ShHTL7 nor the constitutive karrikin signaling mutant smax1-2 confer insensitivity to ABA. These results suggest ShHTL7 requires functional BR perception to bypass the GA requirement for germination.
PMID: 33300428