Exploration of the signaling pathway involving OsCSN8 in regulating the leaf angle of rice.

Leaf angle serves as a crucial determinant of rice plant architecture. The erect leaf phenotype is widely regarded as ideal for achieving high yields. We observed that OsCSN8 overexpression induced leaf erectness at the heading stage, indicating that OsCSN8 regulated leaf angle. This study focused on OsCSN8, a core subunit of COP9 signalosome (CSN), analyzing leaf angle phenotypes in OsCSN8 mutants under varied phytohormone treatments. Integrating Western blot, Bimolecular Fluorescence Complementation, and Yeast Two-Hybrid data elucidated the molecular mechanism: OsCSN8 modulates the second complete leaf angle by interacting with OsBZR1, a central brassinosteroid (BR) signaling transcription factor. Furthermore, at the heading stage, OsCSN8 affected the leaf angle of rice flag leaf by regulating the thickness of adaxial parenchyma and the number of cell layers. These findings reveal the functional role of OsCSN8 in the regulation of rice leaf angle and offer valuable genetic resources for breeding programs focused on agronomic trait improvement.