RT Journal Article SR Electronic T1 The rice G protein γ subunit qPE9-1 positively regulates grain-filling process by interacting with abscisic acid and auxin JF bioRxiv FD Cold Spring Harbor Laboratory SP 487850 DO 10.1101/487850 A1 Dongping Zhang A1 Minyan Zhang A1 Yong Zhou A1 Yuzhu Wang A1 Hongyingxue Chen A1 Weifeng Xu A1 Lin Zhang A1 Ting Pan A1 Bing Lv A1 Guohua Liang A1 Jiansheng Liang YR 2018 UL http://biorxiv.org/content/early/2018/12/05/487850.abstract AB The rice genome contains a single Gα (RGA1) and Gβ (RGB1) and five Gγ subunits. Recent genetic studies have shown that DEP1/qPE9-1, an atypical putative Gγ protein, is responsible for dense and erect panicles, but the biochemical and molecular mechanisms underlying control of grain size are not well understood. Here, we report that plants carrying qPE9-1 have more endosperm cells per grain than plants contain the qpe9-1 allele. The qPE9-1 line has a higher rate and longer period of starch accumulation than the qpe9-1 line. Additionally, the expression of several key genes encoding enzymes catalyzing sucrose metabolism and starch biosynthesis is higher in the qPE9-1 line than in the qpe9-1 line, especially from the mid to late grain-filling stage. Grains of the qPE9-1 line also have higher contents of two phytohormones, ABA and IAA. Exogenous application of ABA or IAA enhanced starch accumulation and the expression of genes encoding grain-filling-related enzymes in the grains of qPE9-1, whereas only IAA produced these effects in qpe9-1. Based on these results, we conclude that qPE9-1 promotes endosperm cell proliferation and positively regulates starch accumulation largely through ABA and IAA, which enhance the expression of genes encoding starch biosynthesis during the late grain-filling stage.