GSE184400
OsCOMT, encoding a caffeic acid O-methyltransferase in melatonin biosynthesis, increases grain yield through regulating leaf senescence and vascular patterning
Melatonin, a natural phytohormone present in most plants, plays multiple roles in plant growth and stress responses. Although melatonin biosynthesis-related genes have been suggested to possess diverse biological functions, their roles and functional mechanisms in regulating rice grain yield remain largely unexplored. Here, we revealed that a rice caffeic acid O-methyltransferase (OsCOMT) gene is involved in melatonin biosynthesis through in vitro and in vivo evidences. Transgenic assays show OsCOMT significantly delays leaf senescence at the grain filling stage, and then improves photosynthesis efficiency. Further experimental and transcriptomic data suggest that OsCOMT inhibits the degradation of chlorophyll and chloroplast, which in turn delay leaf senescence. Histological analysis also reveals the role of OsCOMT in the development of vascular bundle system in rice. The levels of melatonin and cytokinin were significantly increased in the culm of OsCOMT-overexpression plant relative to those of the wild-type (WT). In the OsCOMT-overexpression line, the cytokinin-biosynthesizing genes were up-regulated and the cytokinin-degrading genes were down-regulated, thereby increasing the cytokinin levels compared with the WT. Thus, OsCOMT-mediated vascular patterning may result from the crosstalk between melatonin and cytokinin. More importantly, OsCOMT significantly increased grain number and yield production of rice in various background, including Nipponbare (NIP) and Suken118 (SK118). Our findings show novel insights into melatonin-mediated leaf senescence and vascular patterning, and provide a new strategy to enhance rice yield production. Overall design: A total of nine samples, including three genotypes. Each genotype was detected  at a time point with 3 replicates.