SRA

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. Overall design: For RNA sequencing analysis, total RNA was extracted from four-week-old long day grown plants using Zymo DirecZol kit (ZYMO RESEARCH). RNA concentrations and quality were analyzed using AATI Fragment Analyzer with Standard Sensitivity RNA Analysis Kit (DNF-489-0500). Approximately 500ng of RNA was used for library construction via the QuantSeq 3' mRNA-Seq Library Prep FWD Kit for Illumina and sequenced on an Illumina HiSeq 2500 (50bp single end reads). FASTQ files for each sample were subject to quality control, trimming and mapped to the Arabidopsis TAIR10 genome using the BlueBee A. thaliana (TAIR10) Lexogen QuantSeq 2.2.2 FWD pipeline.