Rice RuBisCO activase promotes the dark‐induced leaf senescence by enhancing the degradation of filamentation temperature‐sensitive H

SUMMARY Leaf senescence is a complex process that is triggered by many developmental and environmental factors. However, the mechanisms regulating leaf senescence remain unclear. Here, we revealed that rice ribulose‐1,5‐bisphosphate carboxylase/oxygenase activase (RCA) promotes the onset of basal dark‐induced senescence. RCA was mainly expressed in the leaves, and its expression level quickly declined under dark conditions. Furthermore, rca mutant plants presented a prolonged leaf longevity phenotype in the dark, whereas overexpression of the large isoform of RCA ( RCA L ), not small isoform ( RCA S ), in rice and Arabidopsis accelerated leaf senescence. Filamentation temperature‐sensitive H (OsFtsH1), a zinc metalloprotease, interacts with RCA L and RCA S and presents a higher binding efficiency to RCA L than RCA S in darkness. Furthermore, we found that RCA L promotes 26S proteasome‐mediated degradation of OsFtsH1 protein, which can be inhibited by protease inhibitor MG132. Consequently, OsFtsH1 loss‐of‐function mutants exhibit accelerated leaf senescence, whereas OsFtsH1 ‐overexpressing plants display delayed senescence. Collectively, our findings highlight the significant role of RCA L isoform in regulating leaf senescence under dark conditions, particularly through enhancing the degradation of OsFtsH1.