OsARF4 Regulates Leaf Inclination via Auxin and Brassinosteroids Pathways in Rice

To understand the molecular mechanisms of leaf inclination regulation, we constructed an auxin response factor (arf) mutant with increased leaf inclination by CRISPR/Cas 9 gene editing technology named osarf4 in rice. OsARF4 encodes a nuclear protein and expresses in the lamina joint (LJ) at different developmental stages in rice. RNA-sequencing analysis revealed that genes related in brassinosteroids (BR) biosynthesis and BR response changed in mutant and overexpression line of OsARF4, suggests that OsARF4 participates in the BR signal pathway. Moreover, BR sensitivity assay uncovered that OsARF4-overexpression line were more sensitive to exogenous BR treatment. In conclusion, OsARF4, as a transcription factor in auxin signaling, participates in the regulatory of leaf inclination, and links auxin and BR signaling. Our results provide a novel insight in leaf inclination regulation, and have significant implications for improving rice architecture and grain yield.