The multifunctional protein OsAIM1 regulates floret opening and closure timing via jasmonic acid-mediated lodicule dynamics in rice

Rice (Oryza sativa) indica and japonica inter-subspecific hybrids hold significant potential for increasing yields. However, differences in diurnal flower-opening time (DFOT) between the 2 subspecies limit the effective exploitation of this heterosis. Additionally, the timing of post-anthesis glume closure (PAGC) affects both hybrid seed yield and quality. Despite their importance, the molecular mechanisms underlying these processes, particularly glume closure, remain poorly understood. In this study, we identify OsAIM1 as a pivotal regulator of both DFOT and PAGC in rice. The aim1-2 mutant exhibits delayed DFOT and impaired PAGC while maintaining normal floret structure, emphasizing its crucial role in floret dynamics. OsAIM1 is highly expressed in lodicules and encodes a peroxisome-localized multifunctional protein. Functional analyses reveal that OsAIM1 regulates lodicule swelling during floret opening and withering post-anthesis, processes essential for glume movement. We further demonstrate that OsAIM1-dependent jasmonic acid biosynthesis is indispensable for coordinating floret opening and closure and influences sugar transport to ensure proper lodicule dynamics. Importantly, natural variation in the OsAIM1 coding region contributes to DFOT divergence between japonica and indica subspecies, providing a molecular basis for their asynchronous flowering. These findings establish OsAIM1 as a key regulator of floret dynamics and a promising molecular target for synchronizing flowering in hybrid rice production.