Grain size is a major determinant of grain weight, a key component of grain yield of rice. Here, we identified the grain size gene WIDE GRAIN 7 (WG7) from a T-DNA insertion mutant. The grain size of WG7 knockout mutants and WG7 overexpression lines indicated that WG7 is a positive regulator of grain size. WG7 encodes a cysteine-tryptophan (CW) domain-containing transcriptional activator. EMSAs and ChIP-qPCR assay confirmed that WG7 directly bound to the promoter of OsMADS1, a grain size gene, and thereby significantly activated its expression. Point mutations showed that the cis-element CATTTC motif in the promoter was the binding site of WG7. Compared with the wild-type, deletion mutants of the cis-element motif exhibited lower expression of OsMADS1 and produced narrower grains, implicating the requirement of this motif for WG7 function. ChIP-qPCR assays showed that WG7 enhanced histone H3K4me3 enrichment in the promoter of OsMADS1. WG7 underwent directional selection due to the poor fertility of the non-functional mutant. These findings demonstrated that WG7 upregulated OsMADS1 expression by directly binding to its promoter, enhanced histone H3K4me3 enrichment in the promoter and ultimately increased grain width. This study will enrich the knowledge concerning the regulatory network of grain size formation in rice.

中文翻译：

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宽谷粒7通过增强水稻（Oryza sativa L.）的OsMADS1启动子中的H3K4me3富集来增加谷粒宽度。

谷物大小是决定谷物重量的主要因素，谷物重量是水稻谷物产量的重要组成部分。在这里，我们从T-DNA插入突变体中鉴定了晶粒尺寸基因WIDE GRAIN 7（WG7）。WG7敲除突变体的晶粒尺寸和WG7过表达谱系表明WG7是晶粒尺寸的正调节剂。WG7编码包含半胱氨酸-色氨酸（CW）域的转录激活因子。EMSAs和ChIP-qPCR分析证实WG7直接与OsMADS1（一种晶粒大小的基因）的启动子结合，从而显着激活了它的表达。点突变表明启动子中的顺式CATTTC基序是WG7的结合位点。与野生型相比，顺式元件基序的缺失突变体表现出较低的OsMADS1表达并产生更窄的颗粒，这暗示了该基序对WG7功能的要求。ChIP-qPCR分析表明，WG7增强了组蛋白H3K4me3在OsMADS1启动子中的富集。由于无功能突变体的育性差，WG7进行了定向选择。这些发现表明，WG7通过直接与其启动子结合而上调了OsMADS1表达，增强了组蛋白H3K4me3在启动子中的富集并最终增加了晶粒宽度。这项研究将丰富有关水稻籽粒大小形成调控网络的知识。增强了组蛋白H3K4me3在启动子中的富集并最终增加了晶粒宽度。这项研究将丰富有关水稻籽粒大小形成调控网络的知识。增强了组蛋白H3K4me3在启动子中的富集并最终增加了晶粒宽度。这项研究将丰富有关水稻籽粒大小形成调控网络的知识。