State Key Laboratory for Crop Genetics and Germplasm Enhancement, Jiangsu Nanjing National Field Scientific Observation and Research Station for Rice Germplasm, Nanjing Agricultural University, Nanjing 210095, China.
Zhongshan Biological Breeding Laboratory, No. 50 Zhongling Street, Nanjing 210095, China.
Plant Physiol. 2024 Oct 1;196(2):948-960. doi: 10.1093/plphys/kiae331.
Grain size is one of the most important traits determining crop yield. However, the mechanism controlling grain size remains unclear. Here, we confirmed the E3 ligase activity of DECREASED GRAIN SIZE 1 (DGS1) in positive regulation of grain size in rice (Oryza sativa) suggested in a previous study. Rice G-protein subunit gamma 2 (RGG2), which negatively regulates grain size, was identified as an interacting protein of DGS1. Biochemical analysis suggested that DGS1 specifically interacts with canonical Gγ subunits (rice G-protein subunit gamma 1 [RGG1] and rice G-protein subunit gamma 2 [RGG2]) rather than non-canonical Gγ subunits (DENSE AND ERECT PANICLE 1 [DEP1], rice G-protein gamma subunit type C 2 [GCC2], GRAIN SIZE 3 [GS3]). We also identified the necessary domains for interaction between DGS1 and RGG2. As an E3 ligase, DGS1 ubiquitinated and degraded RGG2 via a proteasome pathway in several experiments. DGS1 also ubiquitinated RGG2 by its K140, K145, and S147 residues. Thus, this work identified a substrate of the E3 ligase DGS1 and elucidated the post-transcriptional regulatory mechanism of the G-protein signaling pathway in the control of grain size.
粒型是决定作物产量的最重要特征之一。然而，控制粒型的机制仍不清楚。在这里，我们证实了之前研究中提出的 DECREASED GRAIN SIZE 1（DGS1）作为 E3 连接酶在正调控粒型中的作用。先前研究表明，负调控粒型的水稻 G 蛋白亚基γ2（RGG2）是 DGS1 的相互作用蛋白。生化分析表明，DGS1 特异性地与典型的 Gγ亚基（水稻 G 蛋白亚基γ 1 [RGG1]和水稻 G 蛋白亚基γ 2 [RGG2]）相互作用，而不是非典型的 Gγ亚基（致密 erect 穗 1 [DEP1]、水稻 G 蛋白γ 亚基 C 2 [GCC2]、粒型 3 [GS3]）。我们还确定了 DGS1 与 RGG2 相互作用所必需的结构域。作为一种 E3 连接酶，DGS1 通过几种实验中的蛋白酶体途径泛素化和降解 RGG2。DGS1 还通过其 K140、K145 和 S147 残基泛素化 RGG2。因此，这项工作鉴定了 E3 连接酶 DGS1 的底物，并阐明了 G 蛋白信号通路在控制粒型中的转录后调控机制。
