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:The capacity for sustained cell division is a critical determinant of plant meristem development, and ultimately, organ size. This capacity is diminished in mutants lacking the microtubule-associated protein CLASP, and when brassinosteroid signaling is increased. Here, we discovered that CLASP is both targeted by and promotes activity of the brassinosteroid pathway in Arabidopsis root apical meristems. We show that enhanced brassinosteroid signalling reduces CLASP transcript and protein levels, and dramatically shifts microtubule organization to promote exit from the cell division cycle. Notably, CLASP sustains brassinosteroid signalling by fostering retrieval of endocytosed BRI1 receptors to the plasma membrane through the tethering of SNX1 vesicles to microtubules. clasp-1 null mutants have fewer BRI1 receptors, and impaired BR-mediated transcriptional activity and responses. Global transcript profiling confirmed the collapse of cell cycle activity in clasp-1 and revealed hormone crosstalk. Together, these findings reveal an unprecedented form of negative feedback that supports meristem homeostasis.
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: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:The mechanisms ensuring balanced growth remain a critical question in developmental biology. In plants, this balance relies on spatiotemporal integration of hormonal signaling pathways, but the understanding of the precise contribution of each hormone is just beginning to take form. Brassinosteroid (BR) hormone, is shown here to have opposing effects on root meristem size, depending on its site of action. BR is demonstrated to both delay and promote onset of stem cell daughter differentiation, when acting in the outer tissue of the root meristem, the epidermis, and the inner-most tissue, the stele, respectively. To understand the molecular basis of this phenomenon, a comprehensive spatiotemporal translatome mapping of Arabidopsis roots was performed. Analyses of wild type and mutants featuring different distributions of BR, revealed autonomous, tissue-specific gene responses to BR, implying its contrasting tissue-dependent impact on growth. BR-induced genes were primarily detected in epidermal cells of the basal meristem zone and were enriched by auxin-related genes. In contrast, repressed BR genes prevailed in the stele of the apical meristem zone. Furthermore, auxin was found to mediate the growth-promoting impact of BR signaling originating in the epidermis, while BR signaling in the stele buffered this effect. We propose that context-specific BR activity and responses are oppositely interpreted at the organ level, ensuring coherent growth.
Project description:miR394 and its target gene LEAF CURLING RESPONSIVENESS are involved in BR signaling by affecting BRASSINOSTEROID INSENSITIVE2 accumulation.
Project description:Brassinosteroid (BR) and auxin co-regulate plant growth in a process termed cross-talking. Based on the assumption that their signal transductions are partially shared, inhibitory chemicals for both signal transductions were screened from a commercially-available library. A chemical designated as NJ15 (ethyl 2-[5-(3,5-dichlorophenyl)-1,2,3,4-tetrazole-2-yl]acetate) diminished the growth promotion of both adzuki bean epicotyls and Arabidopsis seedlings, by either the application of BR or auxin. To understand its target site(s), bioassays with a high dependence on either the signal transduction of BR (BR-signaling) or of auxin (AX-signaling), were performed. NJ15 inhibited photomorphogenesis of Arabidopsis seedlings grown in the dark, which mainly depends on BR-signaling, while NJ15 also inhibited their gravitropic responses mainly depending on AX-signaling. On the study for the structure-activity relationships of NJ15 analogues, they showed strong correlations on the inhibitory profiles between BR- and AX-signalings. These correlations imply that NJ15 targets the downstream pathway after the integration of BR- and AX-signals.
Project description:Drought is a critical issue in modern agriculture, therefore there is a need to create crops with drought resilience. The complexity of plant responses to abiotic stresses, particularly in the field of brassinosteroid (BR) signaling, has been the subject of extensive research. In this study, we unveil compelling insights indicating that the BRASSINOSTEROID INSENSITIVE 1 (BRI1) receptor in Arabidopsis and Sorghum plays a critical role as a negative regulator of drought responses. Introducing untargeted mutation in the sorghum BRI1 receptor (SbBRI1) effectively enhances the plant ability to withstand osmotic and drought stress. Through DNA Affinity Purification sequencing (DAP-Seq) we show that the sorghum BRI1-EMS-SUPPRESSOR 1 (SbBES1) transcription factor, a downstream player of the BR signaling, binds to a conserved G-box binding motif, and it is responsible for regulating BR homeostasis, as its Arabidopsis ortholog AtBES1. We further characterized the drought tolerance of sorghum bri1 mutants and decipher SbBES1-mediated regulation of phenylpropanoid pathway. Our findings suggest that SbBRI1 signaling serves as a dual purpose: under normal conditions, it regulates lignin biosynthesis by SbBES1, but during drought conditions, BES1 becomes less active, allowing the activation of the flavonoid pathway. This adaptive shift improves the photosynthetic rate and photoprotection, reinforcing crop adaptation to drought.
Project description:Brassinosteroid (BR) is an essential hormone in plant growth and development. BR signaling pathway has been extensively studied, in which Brassinazole resistant 1 (BZR1) functions as a key regulator. Here, we carried out a functional study of the homolog of BZR1 in Medicago truncatula, whose expression was induced in nodules upon rhizobial inoculation. We identified a loss-of-function mutant mtbzr1-1 and generated 35S:MtBZR1 transgenic lines for further analysis at the genetic level. Both the mutant and the overexpressor lines of MtBZR1 showed no obvious phenotypic changes under normal growth condition. After rhizobial inoculation, however, the shoot and root dry mass was reduced in mtbzr1-1 compared with the wild-type, caused by partially impaired nodule development. The transcriptomic analysis identified 1,319 differentially expressed genes in mtbzr1-1 compared with wild-type, many of which are involved in nodule development and secondary metabolite biosynthesis. Our results demonstrate an essential role of MtBZR1 in nodule development in M. truncatula, shedding light on the potential role of BR in legume-rhizobium symbiosis.
Project description:Plant hormone brassinosteroids (BRs) and abscisic acids (ABA) antagonistically regulate many aspects of plant growth and responses. This study analyzes the molecular mechanisms by which regulate the crosstalk between BR and ABA signaling.Various BR deficient and gain-of-function signaling mutants were used to analyze their responses to ABA inhibited primary root growth. RNA sequencing was performed to identify the ABA regulated root genes that are also regulated by BR signaling components.Our result demonstrated that BR signaling negative regulates plant ABA response, and the crosstalk is mediated by BIN2 and BZR1. RNA sequencing has identified subsets of ABA responsive root genes that were regulated by BIN2 and/or BZR1. ChIP-qPCR and EMSA assays showed that BZR1 could bind directly with several G-box cis-elements on ABI5 promoter, suppress the expression of ABI5 and makes plant insensitive to ABA.These data demonstrated that ABI5 is a BZR1 direct targeted gene. Regulation of ABI5 expression by BZR1 plays important roles in regulating the crosstalk between BR and ABA signaling pathways.