The transcription factor OsWRKY36 regulates lamina joint development and the leaf angle in rice by modulating brassinosteroid signalling [DAP-seq]

WRKY transcription factors constitute a crucial protein superfamily that plays a vital role in orchestrating diverse responses to environmental stimuli in plants. Although considerable research has been conducted on the stress resistance mechanisms associated with WRKYs, little is known about the roles of WRKYs in regulating plant growth and development. Here, we identified a key regulator of the rice leaf angle and plant architecture, OsWRKY36, from a rice oswrky mutant library. OsWRKY36 is highly expressed in the leaf lamina joint and promotes cell growth and expansion in adaxial parenchyma cells, leading to a greater leaf angle. A mechanistic investigation revealed that OsPUB24, an E3 ubiquitin ligase that is inhibited by brassinosteroid (BR), interacts with and facilitates the ubiquitination and degradation of OsWRKY36. Genetic evidence indicated that OsWRKY36 acts downstream of OsPUB24 to regulate the BR-induced increase in the leaf angle. Furthermore, OsWRKY36 physically interacts with DLT, a positive regulator of BR, and cooperatively activates the expression of the BR response gene OsBZR4. Thus, BR facilitates the degradation of OsPUB24, leading to enhanced stability of the OsWRKY36 protein. Consequently, a substantial quantity of OsWRKY36 interacts with DLT, thereby inducing the expression of OsBZR4 and ultimately exerting a positive regulatory effect on BR-induced leaf inclination. Collectively, our findings reveal the mechanism underlying the regulation of leaf inclination and plant architecture by the BR-OsPUB24-OsWRKY36 and DLT-OsWRKY36-OsBZR4 modules and thus provide an innovative strategy for optimizing crop production by manipulating the BR signalling pathway. Overall design: To identify the downstream target genes bound by the transcription factor OsWRKY36 in rice, we conducted a DNA affinity purification sequencing (DAP-seq) assay. The MBP-OsWRKY36 protein was synthesized in vitro, and a genomic DNA library (200~800 bp) derived from Nipponbare (Oryza sativa japonica variety) was used for the DNA affinity purification assay. MBP was used as a negative control.