Collaborative Innovation Center of Henan Grain Crops, Henan Agricultural University, Zhengzhou, China.
Key Laboratory of Rice Biology in Henan Province, Henan Agricultural University, Zhengzhou, China.
Plant Biotechnol J. 2019 Apr;17(4):712-723. doi: 10.1111/pbi.13009. Epub 2018 Oct 8.
Rice grain filling rate contributes largely to grain productivity and accumulation of nutrients. MicroRNAs (miRNAs) 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 miRNA regulation of grain filling and rice yield, in consequence. Here, we show that suppressed expression of rice miR1432 (STTM1432) 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 (OsACOT), which is conserved with ACOT13 in other species, as a major target of miR1432 by cleavage. Moreover, overexpression of miR1432-resistant form of OsACOT (OXmACOT) resembled the STTM1432 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 OsACOT 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 OsACOT, which is consistent with the increased levels of auxin and abscisic acid in STTM1432 and OXmACOT plants. Overall, miR1432-OsACOT module plays an important role in grain filling in rice, illustrating its capacity for engineering yield improvement in crops.
水稻粒重对产量和养分积累有重要贡献。miRNAs（miRNA）是植物发育和生理的关键调节因子，成为工程粒型和作物产量的新的关键靶标。然而，到目前为止，很少有研究表明 miRNA 对籽粒灌浆和水稻产量的调节作用。在这里，我们表明，水稻 miR1432（STTM1432）的表达受到抑制，通过提高灌浆速率显著提高了粒重，导致大田试验中整体产量增加了 17.14%。分子分析鉴定出水稻酰基辅酶 A 硫酯酶（OsACOT）是 miR1432 的主要靶标，通过切割将其切割。此外，过表达 miR1432 抗性形式的 OsACOT（OXmACOT）类似于 STTM1432 植株，即通过提高灌浆速率，粒重增加了 46.69%。进一步的研究表明，OsACOT 参与了中链脂肪酸的生物合成。此外，通过改变 miR1432 表达的转基因植物的 RNA-seq 转录组分析表明，miR1432 调控网络的下游基因参与脂肪酸代谢和植物激素生物合成，并且与 OsACOT 共表达基因的富集分析重叠，这与 STTM1432 和 OXmACOT 植物中生长素和脱落酸水平的增加一致。总的来说，miR1432-OsACOT 模块在水稻灌浆中起着重要作用，说明其在作物产量改良工程中的潜力。
