The transcription factor OsWRKY36 regulates leaf angle in rice by modulating brassinosteroid signalling

WRKY transcription factors orchestrate 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 OsWRKY36, a key regulator of rice (Oryza sativa) leaf angle and plant architecture, from a rice oswrky mutant library. OsWRKY36 is strongly expressed in the leaf lamina joint and promotes cell growth and expansion in adaxial parenchyma cells, leading to an increased leaf angle. A mechanistic investigation revealed that the E3 ubiquitin ligase OsPUB24, a negative component of brassinosteroid (BR) signaling, interacts with OsWRKY36 and facilitates its ubiquitination and degradation. Genetic evidence indicated that OsWRKY36 acts downstream of OsPUB24 to regulate the BR-induced increase in leaf angle. Furthermore, OsWRKY36 physically interacts with DWARF AND LOW-TILLERING (DLT), a positive regulator of BR, and cooperatively activates the expression of the BR-responsive gene OsBZR4. BR signaling stabilizes OsWRKY36 by inhibiting OsPUB24, allowing accumulated OsWRKY36 to interact with DLT and drive OsBZR4 expression, thereby positively regulating leaf inclination. Collectively, our study elucidates the mechanism underlying the regulation of leaf inclination and plant architecture by the BR-OsPUB24-OsWRKY36 and DLT-OsWRKY36-OsBZR4 modules. These findings not only advance the understanding of BR-mediated growth regulation but also offer a potential strategy for optimizing crop architecture through modulation of BR signaling.