OsCOMT, encoding a caffeic acid O‐methyltransferase in melatonin biosynthesis, increases rice grain yield through dual regulation of leaf senescence and vascular development

Abstract

Summary Melatonin, a natural phytohormone in plants, plays multiple critical 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 uncovered the roles of a caffeic acid O‐methyltransferase (OsCOMT) gene in mediating rice grain yield through dual regulation of leaf senescence and vascular development. In vitro and in vivo evidence revealed that OsCOMT is involved in melatonin biosynthesis. Transgenic assays suggested that OsCOMT significantly delays leaf senescence at the grain filling stage by inhibiting degradation of chlorophyll and chloroplast, which, in turn, improves photosynthesis efficiency. In addition, the number and size of vascular bundles in the culms and leaves were significantly increased in the OsCOMT‐overexpressing plants, while decreased in the knockout plants, suggesting that OsCOMT plays a positive role in vascular development of rice. Further evidence indicated that OsCOMT‐mediated vascular development might owe to the crosstalk between melatonin and cytokinin. More importantly, we found that OsCOMT is a positive regulator of grain yield, and overexpression of OsCOMT increase grain yield per plant even in a high‐yield variety background, suggesting that OsCOMT can be used as an important target for enhancing rice yield. Our findings shed novel insights into melatonin‐mediated leaf senescence and vascular development and provide a possible strategy for genetic improvement of rice grain yield.

Melatonin-mediated temperature stress tolerance in plants

“…Through the dual regulation of leaf senescence and vascular development, a recent study discovered the involvement of a caffeic acid O-methyltransferase ( OsCOMT ) gene in modulating rice grain yield. 127 The results revealed that OsCOMT is involved in the production of MET. 127 According to transgenic assays, OsCOMT dramatically slowed down the senescence of leaves at the grain-filling stage by preventing the breakdown of Chl and chloroplast, which boosted the effectiveness of photosynthesis.…”

“… 127 The results revealed that OsCOMT is involved in the production of MET. 127 According to transgenic assays, OsCOMT dramatically slowed down the senescence of leaves at the grain-filling stage by preventing the breakdown of Chl and chloroplast, which boosted the effectiveness of photosynthesis. Briefly, MET-mediated leaf senescence and vascular development offer a potential method for genetically enhancing rice grain output.…”

The Antioxidant Cyclic 3-Hydroxymelatonin Promotes the Growth and Flowering of Arabidopsis thaliana

“…Although ascorbic acid and 3-OHM are antioxidants, they have different biological functions in flowering. Further studies of melatonin and its metabolites (e.g., 2-OHM and 3-OHM) will shed light on their biological functions and interactions in plants [ 7 , 25 , 46 , 51 , 52 , 53 , 54 ].…”

Genetic and molecular factors in determining grain number per panicle of rice

“…Knock down of OsTAL reduced the number and area of stem lvbs, and significantly decreased GN and grain yield ( Yang et al, 2015 ). The OsCOMT ( caffeic acid O-methyl transferase ) gene, which encodes the rate-limiting enzyme in melatonin biosynthesis, positively regulates GN and grain yield through promoting vascular development and delaying leaf senescence ( Huangfu et al, 2022 ). Overexpression of OsCOMT can significantly improve the vascular bundle size and number, and increase GN ( Huangfu et al, 2022 ).…”

“…The OsCOMT ( caffeic acid O-methyl transferase ) gene, which encodes the rate-limiting enzyme in melatonin biosynthesis, positively regulates GN and grain yield through promoting vascular development and delaying leaf senescence ( Huangfu et al, 2022 ). Overexpression of OsCOMT can significantly improve the vascular bundle size and number, and increase GN ( Huangfu et al, 2022 ). It is suggested that the improved vascular system (flow) may promote the translocation of photoassimilates from source to sink organs ( Li et al, 2018b ).…”