Interactions between reactive oxygen species stress and brassinosteroid hormone signaling in Arabidopsis seedlings
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ABSTRACT: We were interested in investigating the transcriptome responses to exogenous applications of brassinosteroid hormone when Arabidopsis seedlings are pre-stressed with a reactive oxygen species, hydrogen peroxide. We were interested in seeing which subsets of BR-responsive gene transcripts were most affected and how BR-responsive gene transcripts responded to increasing concentrations of hydrogen peroxide both as a whole and individually.
Project description:We were interested in investigating the transcriptome responses to exogenous applications of brassinosteroid hormone when Arabidopsis seedlings are pre-stressed with a reactive oxygen species, hydrogen peroxide. We were interested in seeing which subsets of BR-responsive gene transcripts were most affected and how BR-responsive gene transcripts responded to increasing concentrations of hydrogen peroxide both as a whole and individually. Liquid culture Arabidopsis seedlings are grown under standard conditions. Hydrogen peroxide is added at various concentrations to pre-stress the seedlings. Following this pretreatment, the seedlings are then treated with brassinosteroid (BR) hormone (epi-brassinolide, BL). Following this treatment, seedlings are harvested and total RNA is extracted for genome-wide transcriptome analysis.
Project description:Hydrogen peroxide (H2O2) is an important signaling molecule in plant developmental processes and stress responses. However, whether H2O2-mediated signaling can crosstalk with plant hormone signaling is largely unclear. Here, we show that H2O2 induces oxidation of the BRASSINAZOLE-RESISTANT1 (BZR1) transcription factor, which functions as a master regulator of Brassinosteroid (BR) signaling. Oxidative modification enhances BZR1 transcriptional activity by promoting its interaction with regulators of auxin- and light-signaling, including AUXIN RESPONSE FACTOR6 (ARF6) and PHYTOCHROME INTERACTING FACTOR4 (PIF4). Genome-wide analysis shows that H2O2-dependent regulation of BZR1 activity plays a major role in modifying gene expression related to several BR-mediated biological processes. Furthermore, we show that the thioredoxin TRXh5 can interact with, and catalyze reduction of, BZR1. We conclude that reversible oxidation of BZR1 connects H2O2- and thioredoxin-mediated redox signaling to BR signaling to regulate plant development
Project description:Global analysis of brassinosteroid (BR)-mediated gene expression under abiotic stress identifies BR associated mechanisms of stress tolerance, and new stress-related genes
Project description:Analysis of brassinosteroid (BR) and auxin effects on gene expression in Arabidopsis roots. Our genomic results indicate that BR and auxin induce largely opposite gene expression responses in primary roots.
Project description:miR394 and its target gene LEAF CURLING RESPONSIVENESS are involved in BR signaling by affecting BRASSINOSTEROID INSENSITIVE2 accumulation.
Project description:The functions of AP2/ERF family transcription factors in stress responses are well documented, but their roles in the brassinosteroid (BR)-regulated growth and stress responses have not been established. Here we show that stress-inducible AP2/ERF family transcription factor TINY inhibits BR-regulated growth while promoting drought response. TINY overexpression plants have stunted growth, increased sensitivity to BR biosynthesis inhibitors and compromised BR-responsive gene expression. In contrast, a tiny tiny2 tiny3 triple mutant has increased BR-regulated growth and BR-responsive gene expression. TINY positively regulates drought response by activating drought responsive genes and promoting abscisic acid-mediated stomatal closure. Global gene expression studies revealed that TINY and BRs oppositely regulate genes involved in plant growth and stress response. TINY interacts with and antagonizes BES1 in the regulation of these genes. The GSK3-like protein kinase BIN2, a negative regulator in the BR pathway, phosphorylates and stabilizes TINY, providing a mechanism for BR-mediated down-regulation of TINY to prevent activation of stress response under optimal growth conditions. Taken together, our results demonstrate that TINY is negatively regulated by BR signaling through BIN2 phosphorylation and positively regulates drought response, as well as inhibits BR-mediated plant growth through TINY-BES1 antagonistic interactions. Our results thus provide insight into the coordination of BR-regulated growth and drought responses.
Project description:Brassinosteroid (BR) homeostasis and signaling are crucial for normal growth and development of plants. BR signaling through cell-surface receptor kinases and intracellular components leads to dephosphorylation and accumulation of the nuclear protein BZR1. How BR signaling regulates gene expression, however, remains unknown. Here we show that BZR1 is a transcriptional repressor that has a previously unknown DNA binding domain and binds directly to the promoters of feedback-regulated BR biosynthetic genes. To identify additional BZR1-regulated genes and to understand the BR-regulated transcriptional pathways, we examined the effects of bzr1-1D and det2 mutations on the expression of BR-regulated genes by using the Arabidopsis full-genome oligo microarray (Affymetrix). Microarray analyses identified additional potential targets of BZR1 and illustrated, together with physiological studies, that BZR1 coordinates BR homeostasis and signaling by playing dual roles in regulating BR biosynthesis and downstream growth responses. Keywords: other
Project description:Brassinosteroids (BRs) are a class of 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. 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. Small RNA libraries were constructed from control and epibrassinolide-treated seedlings. 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 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. 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, pseudo genes 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. 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.
Project description:The BRASSINAZOLE-RESISTANT 1 (BZR1) transcription factor family plays an essential role in plant brassinosteroid (BR) signaling, but the signaling mechanism through which BZR1 and its homologs cooperate with certain coactivators to facilitate transcription of target genes remains incompletely understood. In this study, we used an efficient protein interaction screening system to identify blue-light inhibitor of cryptochromes 1 (BIC1) as a new BZR1-interacting protein in Arabidopsis thaliana. We show that BIC1 positively regulates BR signaling and acts as a transcriptional coactivator for BZR1-dependent activation of BR-responsive genes. Simultaneously, BIC1 interacts with the transcription factor PIF4 to synergistically and interdependently activate expression of downstream genes including PIF4 itself, and to promote plant growth. Chromatin immunoprecipitation assays demonstrate that BIC1 and BZR1/PIF4 interdependently associate with the promoters of common target genes. In addition, we show that the interaction between BIC1 and BZR1 is evolutionally conserved in the model monocot plant Triticum aestivum (bread wheat). Together, our results reveal mechanistic details of BR signaling mediated by a transcriptional activation module BIC1/BZR1/PIF4 and thus provide new insights into the molecular mechanisms underlying the integration of BR and light signaling in plants.
Project description:Brassinosteroids (BRs) are a group of plant steroid hormones that play crucial roles various of growth and developmental processes. Biological function and signal transduction pathway of BR has been well characterized in model plants like Arabidopsis and rice. However, their biological roles are still unclear in tree species, especially in an important non-timber plant moso bamboo, which has great ecological and economic value and distinguish fast-growth feature. Here we reported that reduce endogenous brassinosteroid by biosynthesis inhibitor propiconazole reduced both root and shoot growth in seedling stage. Exogenous BR application promoted shoot bract elongation and inclination of lamina joint and bract. Genome-wide transcriptome analysis were performed to identify hundreds of differential expressed genes by BR and propiconazole treatment in shoot and root parts of bamboo seedling, respectively. GO analysis revealed that BR regulates cell wall related genes, hydrogen peroxide catabolic genes and auxin related genes to promote bamboo root development and elongation. Our study identified BR response genes and provides a comprehensive resource for molecular mechanism research of bamboo growth.