Dev Cell , IF:10.092 , 2020 Jul , V54 (2) : P171-182 doi: 10.1016/j.devcel.2020.05.005
Metabolic Cellular Communications: Feedback Mechanisms between Membrane Lipid Homeostasis and Plant Development.
UMR 5200 Membrane Biogenesis Laboratory, CNRS, University of Bordeaux, Batiment A3 - INRAE Bordeaux Aquitaine, 71 Avenue Edouard Bourlaux CS 20032, 33140 Villenave d'Ornon, France. Electronic address: yohann.boutte@u-bordeaux.fr.; Laboratoire Reproduction et Developpement des Plantes, Universite de Lyon, ENS de Lyon, UCB Lyon 1, CNRS, INRAE, 69342 Lyon, France. Electronic address: yvon.jaillais@ens-lyon.fr.
Membrane lipids are often viewed as passive building blocks of the endomembrane system. However, mounting evidence suggests that sphingolipids, sterols, and phospholipids are specifically targeted by developmental pathways, notably hormones, in a cell- or tissue-specific manner to regulate plant growth and development. Targeted modifications of lipid homeostasis may act as a way to execute a defined developmental program, for example, by regulating other signaling pathways or participating in cell differentiation. Furthermore, these regulations often feed back on the very signaling pathway that initiates the lipid metabolic changes. Here, we review several recent examples highlighting the intricate feedbacks between membrane lipid homeostasis and plant development. In particular, these examples illustrate how all aspects of membrane lipid metabolic pathways are targeted by these feedback regulations. We propose that the time has come to consider membrane lipids and lipid metabolism as an integral part of the developmental program needed to build a plant.
PMID: 32502395
Plant Cell , IF:9.618 , 2020 Jul doi: 10.1105/tpc.20.00531
OsGSK2 Integrates Jasmonic Acid and Brassinosteroid Signaling in Rice.
Stockholm University CITY: Stockholm POSTAL_CODE: 10691 Sweden [SE] william.hughes@su.se.
PMID: 32665308
Plant Cell Environ , IF:6.362 , 2020 Jul doi: 10.1111/pce.13846
Balancing growth and adaptation to stress: crosstalk between brassinosteroid and abscisic acid signaling.
State Key Laboratory of Plant Genomics, Institute of Genetics and Developmental Biology, The Innovative Academy of Seed Design, Chinese Academy of Sciences, Beijing, P. R. China.; University of Chinese Academy of Sciences, Beijing, P. R. China.
Plant growth and development are plastic and can adapt to environmental changes. In this process different plant hormones coordinate to modulate plant growth and environmental interactions. In this article, we describe the individual brassinosteroid (BR) and abscisic acid (ABA) signaling pathways, emphasize the specific regulatory mechanisms between ABA and BR responses and discuss how both phytohormones coordinate growth, development and stress responses in plants. BR signaling is essential for plant development, while ABA signaling is activated to ensure plants survive stress. The crosstalk between BR and ABA, especially protein phosphorylation, protein stability control and downstream transcription control of key components of both pathways are discussed in terms of modulating plant development and stress adaptation. This article is protected by copyright. All rights reserved.
PMID: 32671865
Plant J , IF:6.141 , 2020 Jul doi: 10.1111/tpj.14905
The brassinosteroid-responsive xyloglucan endotransglucosylase/hydrolase 19 (XTH19) and XTH23 genes are involved in lateral root development under salt stress in Arabidopsis.
Laboratory of Photosynthesis and Environment, CAS Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, No. 300 Fenglin Road, Shanghai, 200032, China.; Institute of Photomedicine, Shanghai Skin Disease Hospital, Tongji University School of Medicine, No. 1278 BaoDe Road, Shanghai, 200443, China.
Lateral roots (LRs) are the main component of the root system architecture in Arabidopsis. The plasticity of LR development has an important role in improving plant survival in response to the external environment. Previous studies have revealed a number of genetic pathways that control plant growth in response to environmental stimuli. Here, we find that the xyloglucan endotransglucosylase 19 (XTH19) and XTH23 genes are involved in LR development under salt stress. The density of LRs was decreased in the xth23 single mutant, which was also more sensitive to salt than the wild type, and the xth19xth23 double mutant exhibited additive downregulated LR initiation and salt sensitivity compared with the single mutant. On the contrary, constitutive overexpression of XTH19 or XTH23 caused increased LR densities. Furthermore, XTH19 and XTH23 were induced by salt via the key brassinosteroid signaling pathway transcription factor BES1. In addition, we found that 35S::BES1 increased salt tolerance and the phenotype of xth19xth23 & 35S::BES1 was partially complementary to the wild-type level. In vivo and in vitro assays demonstrated that BES1 acts directly upstream of XTH19 and XTH23 to control their expression. Overall, our results revealed that XTH19 and XTH23 are involved in LR development via the BES1-dependent pathway, and contribute to LR adaptation to salt.
PMID: 32656780
Int J Mol Sci , IF:4.556 , 2020 Jul , V21 (14) doi: 10.3390/ijms21145052
Synergistic Interaction of Phytohormones in Determining Leaf Angle in Crops.
State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangdong Provincial Key Laboratory of Plant Molecular Breeding, South China Agricultural University, Guangzhou 510642, China.; Guangdong Laboratory of Lingnan Modern Agriculture, Guangzhou 510642, China.; State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, College of Life Sciences, South China Agricultural University, Guangzhou 510642, China.
Leaf angle (LA), defined as the angle between the plant stem and leaf adaxial side of the blade, generally shapes the plant architecture into a loosen or dense structure, and thus influences the light interception and competition between neighboring plants in natural settings, ultimately contributing to the crop yield and productivity. It has been elucidated that brassinosteroid (BR) plays a dominant role in determining LA, and other phytohormones also positively or negatively participate in regulating LA. Accumulating evidences have revealed that these phytohormones interact with each other in modulating various biological processes. However, the comprehensive discussion of how the phytohormones and their interaction involved in shaping LA is relatively lack. Here, we intend to summarize the advances in the LA regulation mediated by the phytohormones and their crosstalk in different plant species, mainly in rice and maize, hopefully providing further insights into the genetic manipulation of LA trait in crop breeding and improvement in regarding to overcoming the challenge from the continuous demands for food under limited arable land area.
PMID: 32709150
Int J Mol Sci , IF:4.556 , 2020 Jul , V21 (14) doi: 10.3390/ijms21145096
Insights into Metabolic Reactions of Semi-Dwarf, Barley Brassinosteroid Mutants to Drought.
Institute of Biology, Biotechnology and Environmental Protection, Faculty of Natural Sciences, University of Silesia, Jagiellonska 28, 40-032 Katowice, Poland.; Department of Plant Breeding, Physiology and Seed Science, University of Agriculture in Krakow, 30-239 Krakow, Poland.; The Franciszek Gorski Institute of Plant Physiology, Polish Academy of Sciences, 30-239 Krakow, Poland.; Department of Chemistry and Biochemistry, Institute of Basic Sciences, University of Physical Education, 31-571 Krakow, Poland.
The roles of endogenous brassinosteroids (BRs) in the modulation of reaction to drought and genetic regulation of this process are still obscure. In this study, a multidirectional analysis was performed on semi-dwarf barley (Hordeum vulgare) Near-Isogenic Lines (NILs) and the reference cultivar "Bowman" to get insights into various aspects of metabolic reaction to drought. The NILs are defective in BR biosynthesis or signaling and displayed an enhanced tolerance to drought. The BR metabolism perturbations affected the glucose and fructose accumulation under the control and stress conditions. The BR metabolism abnormalities negatively affected the sucrose accumulation as well. However, during drought, the BR-deficient NILs accumulated higher contents of sucrose than the "Bowman" cultivar. Under the control conditions, accumulation of transcripts encoding antioxidant enzymes ascorbate peroxidase (HvAPX) and superoxide dismutase (HvSOD) was BR-dependent. However, during drought, the accumulation of HvAPX transcript was BR-dependent, whereas accumulations of transcripts encoding catalase (HvCAT) and HvSOD were not affected by the BR metabolism perturbations. The obtained results reveal a significant role of BRs in regulation of the HvAPX and HvCAT enzymatic activities under control conditions and the HvAPX and HvSOD activities during physiological reactions to drought.
PMID: 32707671
Ann Bot , IF:4.005 , 2020 Jul doi: 10.1093/aob/mcaa121
Associations between phytohormones and cellulose biosynthesis in land plants.
School of Biosciences, University of Melbourne, Parkville, Victoria, Australia.; Department of Biochemistry and Molecular Biology, University of Nevada, Reno, Nevada, USA.; Department of Chemistry, University of Nevada, Reno, Nevada, USA.
BACKGROUND: Phytohormones are small molecules that regulate virtually every aspect of plant growth and development; from basic cellular processes, such as cell expansion and division, to whole plant environmental responses. While the phytohormone levels and distribution thus tell the plant how to adjust itself, the corresponding growth alterations are actuated by cell wall modification/synthesis and internal turgor. Plant cell walls are complex polysaccharide-rich extracellular matrixes that surround all plant cells. Among the cell wall components, cellulose is typically the major polysaccharide, and is the load-bearing structure of the walls. Hence, the cell wall distribution of cellulose, which is synthesized by large Cellulose Synthase protein complexes at the cell surface, directs plant growth. SCOPE: Here, we review the relationships between key phytohormone classes and cellulose deposition in plant systems. We present the core signaling pathways associated with each phytohormone and discuss the current understanding of how these signaling pathways impact cellulose biosynthesis with a particular focus on transcriptional and post-translational regulation. Because cortical microtubules underlying the plasma membrane significantly impact the trajectories of Cellulose Synthase Complexes, we also discuss the current understanding of how phytohormone signaling impacts the cortical microtubule array. CONCLUSION: Given the importance of cellulose deposition and phytohormone signaling in plant growth and development, one would expect that there is substantial cross-talk between these processes; however, mechanisms for many of these relationships remain unclear and should be considered as the target of future studies.
PMID: 32619216
Ann Bot , IF:4.005 , 2020 Jul , V126 (2) : P261-275 doi: 10.1093/aob/mcaa077
Processes controlling programmed cell death of root velamen radicum in an epiphytic orchid.
CAS Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan, China.; Center of Plant Ecology, Core Botanical Gardens, Chinese Academy of Sciences, Mengla, Yunnan, China.; Key Laboratory for Economic Plants and Biotechnology, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming, Yunnan, China.; Horticulture Department, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan, China.; Global Ecology, College of Science and Engineering, Flinders University, GPO Box 2100, Adelaide, South Australia, Australia.
BACKGROUND AND AIMS: Development of the velamen radicum on the outer surface of the root epidermis is an important characteristic for water uptake and retention in some plant families, particularly epiphytic orchids, for survival under water-limited environments. Velamen radicum cells derive from the primary root meristem; however, following this development, velamen radicum cells die by incompletely understood processes of programmed cell death (PCD). METHODS: We combined the use of transmission electron microscopy, X-ray micro-tomography and transcriptome methods to characterize the major anatomical and molecular changes that occur during the development and death of velamen radicum cells of Cymbidium tracyanum, a typical epiphytic orchid, to determine how PCD occurs. KEY RESULTS: Typical changes of PCD in anatomy and gene expression were observed in the development of velamen radicum cells. During the initiation of PCD, we found that both cell and vacuole size increased, and several genes involved in brassinosteroid and ethylene pathways were upregulated. In the stage of secondary cell wall formation, significant anatomical changes included DNA degradation, cytoplasm thinning, organelle decrease, vacuole rupture and cell wall thickening. Changes were found in the expression of genes related to the biosynthesis of cellulose and lignin, which are instrumental in the formation of secondary cell walls, and are regulated by cytoskeleton-related factors and phenylalanine ammonia-lyase. In the final stage of PCD, cell autolysis was terminated from the outside to the inside of the velamen radicum. The regulation of genes related to autophagy, vacuolar processing enzyme, cysteine proteases and metacaspase was involved in the final execution of cell death and autolysis. CONCLUSIONS: Our results showed that the development of the root velamen radicum in an epiphytic orchid was controlled by the process of PCD, which included initiation of PCD, followed by formation of the secondary cell wall, and execution of autolysis following cell death.
PMID: 32318689
BMC Genomics , IF:3.594 , 2020 Jul , V21 (1) : P507 doi: 10.1186/s12864-020-06917-z
Enhanced sugar accumulation and regulated plant hormone signalling genes contribute to cold tolerance in hypoploid Saccharum spontaneum.
Sugarcane Research Institute, Yunnan Agricultural University, Kunming, 650201, Yunnan Province, PR China.; Chuxiong normal university, Chuxiong, 675000, Yunnan Province, PR China.; Wenshan Academy of Agricultural Sciences, Wenshan, 663000, Yunnan Province, PR China.; Sugarcane Research Institute, Yunnan Agricultural University, Kunming, 650201, Yunnan Province, PR China. yangqinghui@163.com.; Sugarcane Research Institute, Yunnan Agricultural University, Kunming, 650201, Yunnan Province, PR China. x.h_wang@163.com.
BACKGROUND: Wild sugarcane Saccharum spontaneum plants vary in ploidy, which complicates the utilization of its germplasm in sugarcane breeding. Investigations on cold tolerance in relation to different ploidies in S. spontaneum may promote the exploitation of its germplasm and accelerate the improvement of sugarcane varieties. RESULTS: A hypoploid clone 12-23 (2n = 54) and hyperploid clone 15-28 (2n = 92) of S. spontaneum were analysed under cold stress from morphological, physiological, and transcriptomic perspectives. Compared with clone 15-28, clone 12-23 plants had lower plant height, leaf length, internode length, stem diameter, and leaf width; depressed stomata and prominent bristles and papillae; and thick leaves with higher bulliform cell groups and thicker adaxial epidermis. Compared with clone 15-28, clone 12-23 showed significantly lower electrical conductivity, significantly higher water content, soluble protein content, and superoxide dismutase activity, and significantly higher soluble sugar content and peroxidase activity. Under cold stress, the number of upregulated genes and downregulated genes of clone 12-23 was higher than clone 15-28, and many stress response genes and pathways were affected and enriched to varying degrees, particularly sugar and starch metabolic pathways and plant hormone signalling pathways. Under cold stress, the activity of 6-phosphate glucose trehalose synthase, trehalose phosphate phosphatase, and brassinosteroid-signalling kinase and the content of trehalose and brassinosteroids of clone 12-23 increased. CONCLUSIONS: Compared with hyperploid clone 15-28, hypoploid clone 12-23 maintained a more robust osmotic adjustment system through sugar accumulation and hormonal regulation, which resulted in stronger cold tolerance.
PMID: 32698760
BMC Plant Biol , IF:3.497 , 2020 Jul , V20 (1) : P332 doi: 10.1186/s12870-020-02534-w
TRANSTHYRETIN-LIKE and BYPASS1-LIKE co-regulate growth and cold tolerance in Arabidopsis.
The Key Laboratory of Cell Activities and Stress Adaptations, Ministry of Education, School of Life Sciences, Lanzhou University, Lanzhou, 730000, People's Republic of China.; The Key Laboratory of Cell Activities and Stress Adaptations, Ministry of Education, School of Life Sciences, Lanzhou University, Lanzhou, 730000, People's Republic of China. zhanghua@lzu.edu.cn.; The Key Laboratory of Cell Activities and Stress Adaptations, Ministry of Education, School of Life Sciences, Lanzhou University, Lanzhou, 730000, People's Republic of China. lizhean@lzu.edu.cn.; School of Forestry, Beijing Forestry University, Beijing, 100083, People's Republic of China. lizhean@lzu.edu.cn.
BACKGROUND: Cold stress inhibits normal physiological metabolism in plants, thereby seriously affecting plant development. Meanwhile, plants also actively adjust their metabolism and development to adapt to changing environments. Several cold tolerance regulators have been found to participate in the regulation of plant development. Previously, we reported that BYPASS1-LIKE (B1L), a DUF793 family protein, participates in the regulation of cold tolerance, at least partly through stabilizing C-REPEAT BINDING FACTORS (CBFs). In this study, we found that B1L interacts with TRANSTHYRETIN-LIKE (TTL) protein, which is involved in brassinosteroid (BR)-mediated plant growth and catalyses the synthesis of S-allantoin, and both proteins participate in modulating plant growth and cold tolerance. RESULTS: The results obtained with yeast two hybrid (Y2H) and bimolecular fluorescence complementation (BiFC) assays showed that B1L directly interacted with TTL. Similar to the ttl-1 and ttl-2 mutants, the b1l mutant displayed a longer hypocotyl and greater fresh weight than wild type, whereas B1L-overexpressing lines exhibited a shorter hypocotyl and reduced fresh weight. Moreover, ttl-1 displayed freezing tolerance to cold treatment compared with WT, whereas the b1l mutant and TTL-overexpressing lines were freezing-sensitive. The b1l ttl double mutant had a developmental phenotype and freezing tolerance that were highly similar to those of ttl-1 compared to b1l, indicating that TTL is important for B1L function. Although low concentrations of brassinolide (0.1 or 1 nM) displayed similarly promoted hypocotyl elongation of WT and b1l under normal temperature, it showed less effect to the hypocotyl elongation of b1l than to that of WT under cold conditions. In addition, the b1l mutant also contained less amount of allantoin than Col-0. CONCLUSION: Our results indicate that B1L and TTL co-regulate development and cold tolerance in Arabidopsis, and BR and allantoin may participate in these processes through B1L and TTL.
PMID: 32664862
Plants (Basel) , IF:2.762 , 2020 Jul , V9 (7) doi: 10.3390/plants9070868
In vivo Reporters for Visualizing Alternative Splicing of Hormonal Genes.
Laboratory of Hormonal Regulations in Plants, Institute of Experimental Botany, Czech Academy of Sciences, 165 02 Prague, Czech Republic.; Functional Genomics and Proteomics of Plants, Central European Institute of Technology and National Centre for Biomolecular Research, Masaryk University, 625 00 Brno, Czech Republic.
Rapid progress in plant molecular biology in recent years has uncovered the main players in hormonal pathways and characterized transcriptomic networks associated with hormonal response. However, the role of RNA processing, in particular alternative splicing (AS), remains largely unexplored. Here, using example genes involved in cytokinin signaling, brassinosteroid synthesis and auxin transport, we present a set of reporters devised to visualize their AS events in vivo. These reporters show a differential tissue-specific expression of certain transcripts and reveal that expression of some of the them can be changed by the application of the exogenous hormone. Finally, based on the characterized AS event of the PIN7 auxin efflux carrier, we designed a system that allows a rapid genetic screening for the factors upstream of this AS event. Our innovative toolset can be therefore highly useful for exploring novel regulatory nodes of hormonal pathways and potentially helpful for plant researchers focusing on developmental aspects of AS.
PMID: 32650629
Plants (Basel) , IF:2.762 , 2020 Jul , V9 (7) doi: 10.3390/plants9070840
Knock-Down the Expression of Brassinosteroid Receptor TaBRI1 Reduces Photosynthesis, Tolerance to High Light and High Temperature Stresses and Grain Yield in Wheat.
Institute of Genetics and Developmental Biology, Innovation Academy for Seed Design, Chinese Academy of Sciences, Beijing 100101, China.; National Key Facility for Crop Gene Resources and Genetic Improvement, Institute of Crop Science, Chinese Academy of Agricultural Sciences, Beijing 100081, China.; The Zhao xian experimental station of Hebei Academy of Agriculture and Forestry Sciences, Shijiazhuang 050035, China.
Brassinosteroid (BR)-deficient or -insensitive mutants exhibited altered plant architecture with the potential to impact yield, the underlying physiological and molecular mechanisms are still to be explored. In this study, we cloned three BR receptor homologous genes TaBRI1-A1, -B1 and -D1 from hexaploid wheat (Triticum estivum L.) and further isolated the TaBRI1-A1, TaBRI1-D1 deletion mutants from the ion beam-induced mutants of variety Xiaoyan81, TaBRI1-A1 and TaBRI1-D1 in which the expression of total receptor TaBRI1 was significantly decreased. The TaBRI1 knock-down mutants exhibited relatively erect leaves and a significant decrease in the 1000-grain weight. Further studies showed that TaBRI1 knock-down mutants showed a significant reduction in photosynthetic rate during the whole grain-filling stage. TaBRI1 knock-down plants generated by TaBRI1-A1, TaBRI1-D1 deletion or using virus-induced gene silencing exhibited the reduction in the efficiency of photosystem II (PSII) (Fv/Fm, PhiPSII and electron transport rate, ETR) especially under high light and high temperature stresses. The 24-epibrassinolide (EBR) treatment increased CO2 assimilation rate in the wild type under both normal and high light and high temperature stresses conditions, but this increasing effect was not observed in the TaBRI1 knock-down mutants. Meanwhile, the expression levels of BR biosynthetic genes including TaDWARF4, TaCPD1 and TaCPD90C1 is not decreased or decreased to a lesser extent in the TaBRI1 knock-down mutants after EBR treatment. These results suggested that TaBRI1 is required for maintaining photosynthesis and tolerance to high light and high temperature stresses both of which are important for grain yield and will be a possible engineered target to control plant photosynthesis and yields in wheat.
PMID: 32635376
Plant Signal Behav , IF:1.671 , 2020 Jul : P1789321 doi: 10.1080/15592324.2020.1789321
Different strategies of strigolactone and karrikin signals in regulating the resistance of Arabidopsis thaliana to water-deficit stress.
Institute of Plant Stress Biology, State Key Laboratory of Cotton Biology, Department of Biology, Henan University , Kaifeng, China.; Stress Adaptation Research Unit, RIKEN Center for Sustainable Resource Science , Yokohama, Japan.; Henan Joint International Laboratory for Crop Multi-Omics Research, Henan University , Kaifeng, China.; Department of Life Sciences, POSTECH Biotech Center, Pohang University of Science and Technology , Pohang, Korea.; Agricultural Genetics Institute, Vietnam Academy of Agricultural Sciences , Hanoi, Vietnam.; Key Laboratory of Mollisols Agroecology, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences , Changchun, China.; School of Life Sciences, East China Normal University , Shanghai, China.; Institute of Research and Development, Duy Tan University, 03 Quang Trung, Da Nang, Vietnam; Stress Adaptation Research Unit, RIKEN Center for Sustainable Resource Science , Yokohama, Japan.
Strigolactone and karrikin receptors, DWARF14 (D14) and KARRIKIN INSENSITIVE 2 (KAI2), respectively, have been shown to positively regulate drought resistance in Arabidopsis thaliana by modulating abscisic acid responsiveness, anthocyanin accumulation, stomatal closure, cell membrane integrity and cuticle formation. Here, we aim to identify genes specifically or commonly regulated by D14 and KAI2 under water scarcity, using comparative analysis of the transcriptome data of the A. thaliana d14-1 and kai2-2 mutants under dehydration conditions. In comparison with wild-type, under dehydration conditions, the expression levels of genes related to photosynthesis and the metabolism of glucosinolates and trehalose were significantly changed in both d14-1 and kai2-2 mutant plants, whereas the transcript levels of genes related to the metabolism of cytokinins and brassinosteroids were significantly altered in the d14-1 mutant plants only. These results suggest that cytokinin and brassinosteroid metabolism might be specifically regulated by the D14 pathway, whereas photosynthesis and metabolism of glucosinolates and trehalose are potentially regulated by both D14 and KAI2 pathways in plant response to water scarcity.
PMID: 32669036
Genes Genomics , IF:1.188 , 2020 Aug , V42 (8) : P957-969 doi: 10.1007/s13258-020-00964-2
Genome-wide analysis of brassinosteroid responsive small RNAs in Arabidopsis thaliana.
Department of Life Science and Multidisciplinary Genome Institute, Hallym University, Chuncheon, 24252, Republic of Korea.; Department of Biological Sciences, College of Biological Sciences and Biotechnology, Chungnam National University, Daejeon, 34134, Korea.; Department of Biological Sciences, Louisiana State University, Baton Rouge, LA, 70803, USA.; Department of Life Science and Multidisciplinary Genome Institute, Hallym University, Chuncheon, 24252, Republic of Korea. dhjeong73@hallym.ac.kr.; Department of Biological Sciences, College of Biological Sciences and Biotechnology, Chungnam National University, Daejeon, 34134, Korea. manhooh@cnu.ac.kr.
BACKGROUND: Brassinosteroids (BRs) are a class of phytohormones with important roles in regulating physiological and developmental processes. Small RNAs, including small interfering RNAs and microRNAs (miRNAs), are non-protein coding RNAs that regulate gene expression at the transcriptional and post-transcriptional levels. However, the roles of small RNAs in BR response have not been studied well. OBJECTIVE: In this study, we aimed to identify BR-responsive small RNA clusters and miRNAs in Arabidopsis. In addition, the effect of BR-responsive small RNAs on their transcripts and target genes were examined. METHODS: Small RNA libraries were constructed from control and epibrassinolide-treated seedlings expressing wild-type BRI1-Flag protein under its native promoter in the bri1-5 mutant. After sequencing the small RNA libraries, differentially expressed small RNA clusters were identified by examining the expression levels of small RNAs in 100-nt bins of the Arabidopsis genome. To identify the BR-responsive miRNAs, the expression levels of all the annotated mature miRNAs, registered in miRBase, were analyzed. Previously published RNA-seq data were utilized to monitor the BR-responsive expression patterns of differentially expressed small RNA clusters and miRNA target genes. RESULTS: In results, 38 BR-responsive small RNA clusters, including 30 down-regulated and eight up-regulated clusters, were identified. These differentially expressed small RNA clusters were from miRNA loci, transposons, protein-coding genes, pseudogenes and others. Of these, a transgene, BRI1, accumulates small RNAs, which are not found in the wild type. Small RNAs in this transgene are up-regulated by BRs while BRI1 mRNA is down-regulated by BRs. By analyzing the expression patterns of mature miRNAs, we have identified BR-repressed miR398a-5p and BR-induced miR156g. Although miR398a-5p is down-regulated by BRs, its predicted targets were not responsive to BRs. However, SPL3, a target of BR-inducible miR156g, is down-regulated by BRs. CONCLUSION: BR-responsive small RNAs and miRNAs identified in this study will provide an insight into the role of small RNAs in BR responses in plants. Especially, we suggest that miR156g/SPL3 module might play a role in BR-mediated growth and development in Arabidopsis.
PMID: 32648234