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bioRxiv · 10.1101/487850

The rice G protein γ subunit qPE9-1 positively regulates grain-filling process by interacting with abscisic acid and auxin

Zhang, D.·Zhang, M.·Zhou, Y.·Wang, Y.·Chen, H.·Xu, W.·Zhang, L.·Pan, T.·Lv, B.·Liang, G.·Liang, J.
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Abstract

The rice genome contains a single G (RGA1) and G{beta} (RGB1) and five G{gamma} subunits. Recent genetic studies have shown that DEP1/qPE9-1, an atypical putative G{gamma} 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.

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Zhang, D., Zhang, M., Zhou, Y., Wang, Y., Chen, H., Xu, W., Zhang, L., Pan, T., Lv, B., Liang, G., Liang, J.. 2018-12-05. The rice G protein γ subunit qPE9-1 positively regulates grain-filling process by interacting with abscisic acid and auxin. https://doi.org/10.1101/487850

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