Project description:We report global gene expression profilies of Brassinosteroid related Arabidopsis mutants in response to dehydration and fixed-carbon starvation stresses by RNA-seq
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 effects of brassinosteroid signaling on shoot and root development have been characterized in great detail but did not identify a simple consistent positive or negative impact on a basic cellular parameter. Here we combined digital 3D single-cell shape analysis and single-cell mRNA sequencing to characterize root meristems and mature root segments of brassinosteroid-blind mutants and wildtype. These data demonstrate that brassinosteroid signaling neither affects cell volume nor cell proliferation capacity. Instead, brassinosteroid signaling is essential for the precise orientation of cell division planes and the extent and timing of anisotropic cell expansion. Moreover, we found that the cell-aligning effects of brassinosteroid signaling can propagate to normalize the anatomy of both adjacent and distant brassinosteroid-blind cells through non-cell-autonomous functions, which are sufficient to restore growth vigor. Finally, single-cell transcriptome data discern directly brassinosteroid-responsive genes from genes that can react non-cell-autonomously and highlight arabinogalactans as sentinels of brassinosteroid-dependent anisotropic cell expansion.
Project description:* The high sequence and structural similarities between BRI1 brassinosteroid receptors of Arabidopsis (AtBRI1) and sorghum (SbBRI1) prompted us to study the functionally conserved roles of BRI in both organisms. * Introducing sorghum SbBRI1 in Arabidopsis bri1 mutants restores defective growth and complements developmental phenotypes to WT levels. * Sorghum mutants for SbBRI1 receptors show defective BR sensitivity and results in impaired growth and development throughout the entire sorghum life cycle. Embryonic analysis of sorghum primary roots traced the root growth and development at the early stages, revealing the role of SbBRI1 in BR perception during cell division and BR sensing. RNA-seq of SbBRI1 mutants support the roles of SbBRI1 in cell wall biosynthesis and remodeling. * Together, these results uncover that sorghum SbBRI1 receptor protein play functionally conserved roles in plant growth and development.
Project description:Plants acquire essential elements from inherently heterogeneous soils, in which phosphate and iron availabilities vary. Consequently, plants developed adaptive strategies to cope with low iron and low phosphate levels, including alternation between root growth enhancement and attenuation. How this adaptive response is achieved remains unclear. Here, we found that low iron accelerates the root growth of Arabidopsis thaliana by activating brassinosteroid signaling, whereas low-phosphate-induced high iron accumulation inhibited it. Altered hormone signaling intensity also modulated iron accumulation in the root elongation and differentiation zones, constituting a feedback response between brassinosteroid and iron. Surprisingly, the early effect of low iron levels on root growth required the brassinosteroid receptor but the hormone ligand was negligible. The brassinosteroid receptor inhibitor BKI1, the transcription factors BES1/BZR1 and the ferroxidase LPR1, stood at the base of this feedback loop. Hence, shared brassinosteroid and iron regulatory components link nutrient status to root morphology, thereby driving the adaptive response.
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.