Grain yield in many cereal crops is largely determined by grain size. Here we report the genetic and molecular characterization of GS3, a major quantitative trait locus for grain size. It functions as a negative regulator of grain size and organ size. The wild-type isoform is composed of four putative domains: a plant-specific organ size regulation (OSR) domain in the N terminus, a transmembrane domain, a tumor necrosis factor receptor/nerve growth factor receptor (TNFR/NGFR) family cysteine-rich domain, and a von Willebrand factor type C (VWFC) in the C terminus. These domains function differentially in grain size regulation. The OSR domain is both necessary and sufficient for functioning as a negative regulator. The wild-type allele corresponds to medium grain. Loss of function of OSR results in long grain. The C-terminal TNFR/NGFR and VWFC domains show an inhibitory effect on the OSR function; loss-of-function mutations of these domains produced very short grain. This study linked the functional domains of the GS3 protein to natural variation of grain size in rice.
在許多谷類作物的谷物產(chǎn)量在很大程度上取決于籽粒的大小。在這里，我們報(bào)道了GS3的遺傳和分子鑒定，一個(gè)主效的控制籽粒大小的數(shù)量性狀基因座。它在控制籽粒和器官大小中發(fā)揮著負(fù)調(diào)節(jié)子的功能。野生型等位基因包含有四個(gè)推測(cè)的結(jié)構(gòu)域：N端是一種植物特有的調(diào)節(jié)器官大小的結(jié)構(gòu)域（OSR），一個(gè)跨膜區(qū)，腫瘤壞死因子/神經(jīng)生長(zhǎng)因子受體（TNFR / NGFR）家族富半胱氨酸結(jié)構(gòu)域，以及C端的C型血管性血友病因子（VWFC）。這些結(jié)構(gòu)域在調(diào)節(jié)籽粒大小中發(fā)揮不同的功能。OSR結(jié)構(gòu)域作為一個(gè)負(fù)調(diào)節(jié)子發(fā)揮作用是充分必要的。野生型等位基因?qū)?yīng)形成中等長(zhǎng)度的籽粒。OSR結(jié)構(gòu)功能的丟失會(huì)導(dǎo)致形成長(zhǎng)的籽粒。 C端TNFR/NGFR和VWFC結(jié)構(gòu)域顯示出對(duì)OSR功能的抑制作用；對(duì)這些領(lǐng)域的功能失活突變會(huì)產(chǎn)生非常短的籽粒。本研究將GS3蛋白質(zhì)的結(jié)構(gòu)域的功能與水稻種子籽粒大小的自然變異聯(lián)系了起來(lái)。