Rice ILI atypical bHLH transcription factors antagonize OsbHLH157/OsbHLH158 during brassinosteroid signaling

• DOI: 10.1093/plphys/kiad635
• Publication Date: 2023-12-01T20:31:45Z
• Authors: Mingqian Liu; Mingmin Lu; Ziwei Zhao; Qin Luo; Feng Liu; Jing Zhao; Yubing He; Yanan Tian; Huadong Zhan
• Keywords: Brassinosteroid; Dwarfism; Transcription

Abstract Brassinosteroids (BRs) are a group of steroid hormones that play crucial roles in plant growth and development. Atypical bHLH transcription factors lack the basic region for DNA binding have been implicated BR signaling. However, underlying mechanisms atypical bHLHs regulation rice (Oryza sativa) signaling still largely unknown. Here, we describe systematic characterization INCREASED LEAF INCLINATION (ILI) subfamily rice. A total 8 members, ILI1 to ILI8, with substantial sequence similarity were retrieved. Knockout overexpression analyses demonstrated these ILIs unequally redundant indispensable BR-mediated development rice, more prominent role ILI4 ILI5. The ili3/4/5/8 quadruple ili1/3/4/7/8 quintuple mutants displayed tremendous BR-related defects severe dwarfism, erect leaves, sterility. Biochemical analysis showed interact OsbHLH157 OsbHLH158, which also no obvious transcriptional activity. Overexpression OsbHLH158 led drastic BR-defective growth, whereas osbhlh157 osbhlh158 double mutant developed typical BR-enhanced phenotype, indicating major negative Further transcriptome revealed opposite effects OsbHLH157/OsbHLH158 downstream gene expression, supporting antagonism maintaining balance Our results provide insights into mechanism architecture formation