miR1432‐OsACOT (Acyl‐CoA thioesterase) module determines grain yield via enhancing grain filling rate in rice

Summary Rice grain filling rate contributes largely to grain productivity and accumulation of nutrients. Micro RNA s (mi RNA s) are key regulators of development and physiology in plants and become a novel key target for engineering grain size and crop yield. However, there is little studies, so far, showing the mi RNA regulation of grain filling and rice yield, in consequence. Here, we show that suppressed expression of rice miR1432 ( STTM 1432) significantly improves grain weight by enhancing grain filling rate and leads to an increase in overall grain yield up to 17.14% in a field trial. Molecular analysis identified rice Acyl‐CoA thioesterase ( Os ACOT ), which is conserved with ACOT 13 in other species, as a major target of miR1432 by cleavage. Moreover, overexpression of miR1432‐resistant form of Os ACOT ( OX m ACOT ) resembled the STTM 1432 plants, that is, a large margin of an increase in grain weight up to 46.69% through improving the grain filling rate. Further study indicated that Os ACOT was involved in biosynthesis of medium‐chain fatty acids. In addition, RNA ‐seq based transcriptomic analyses of transgenic plants with altered expression of miR1432 demonstrated that downstream genes of miR1432‐regulated network are involved in fatty acid metabolism and phytohormones biosynthesis and also overlap with the enrichment analysis of co‐expressed genes of Os ACOT , which is consistent with the increased levels of auxin and abscisic acid in STTM 1432 and OX m ACOT plants. Overall, miR1432‐ Os ACOT module plays an important role in grain filling in rice, illustrating its capacity for engineering yield improvement in crops.