Rice Senescence-Induced Receptor-Like Kinase () Is Involved in Phytohormone-Mediated Chlorophyll Degradation.

Chlorophyll breakdown is a vital catabolic process of leaf senescence as it allows the recycling of nitrogen and other nutrients. In the present study, we isolated rice senescence-induced receptor-like kinase (), whose transcription was upregulated in senescing rice leaves. The detached leaves of mutant () contained more green pigment than those of the wild type (WT) during dark-induced senescence (DIS). HPLC and immunoblot assay revealed that degradation of chlorophyll and photosystem II proteins was repressed in during DIS. Furthermore, ultrastructural analysis revealed that leaves maintained the chloroplast structure with intact grana stacks during dark incubation; however, the retained green color and preserved chloroplast structures of did not enhance the photosynthetic competence during age-dependent senescence in autumn. In , the panicles per plant was increased and the spikelets per panicle were reduced, resulting in similar grain productivity between WT and . By transcriptome analysis using RNA sequencing, genes related to phytohormone, senescence, and chlorophyll biogenesis were significantly altered in compared to those in WT during DIS. Collectively, our findings indicate that may degrade chlorophyll by participating in a phytohormone-mediated pathway.