Zhou Wei, Cao Ni, Lv Yusong, Jiao Guiai, Yu Junming, Zhu Maodi, Wu Jiamin, Zhao Rumeng, Liu Yongqiang, Lu Ao, Hu Shikai, Wei Xiangjin, Zhao Fengli, Tang Shaoqing, Shao Gaoneng, Hu Peisong
State Key Laboratory of Rice Biology and Breeding, China National Center for Rice Improvement, China National Rice Research Institute, Hangzhou, 310006, China.
State Key Laboratory of Rice Biology and Breeding, China National Center for Rice Improvement, China National Rice Research Institute, Hangzhou, 310006, China.
Plant Commun. 2025 May 8:101354. doi: 10.1016/j.xplc.2025.101354.
In rice (Oryza sativa), defects in endosperm development can give grains a chalky texture, which decreases grain quality and is therefore undesirable for breeding and marketing. However, the molecular basis of chalkiness remains largely unknown. Here, we identified CHALK10, which encodes an F-box protein that negatively regulates rice chalkiness. The chalk10 mutant exhibited abnormal starch granule development, decreased starch content and alteration of starch physicochemical properties when compared to the wild type. CHALK10 interacts with the gibberellin (GA) oxidase SEMIDWARF-1 (SD1) and promotes the ubiquitination and degradation of SD1 through the 26S proteasome pathway. The grains of SD1-overexpressing plants had increased chalkiness, and introducing the sd1 mutant into the chalk10 background largely suppressed the higher chalkiness seen in the chalk10 mutant. GA levels were higher in the chalk10 mutant compared to the wild type, and application of the bioactive GA form GA increased the chalkiness of grains. The expression of genes related to starch degradation or biosynthesis was altered in the chalk10 mutant, resulting in diminished starch production and higher metabolizable sugar contents in the endosperm. In summary, our findings reveal a novel mechanism that regulates chalkiness and provide potential targets for improving rice quality.
在水稻（Oryza sativa）中，胚乳发育缺陷会使谷粒呈现粉质质地，这会降低谷粒品质，因此对于育种和销售来说是不理想的。然而，垩白的分子基础在很大程度上仍然未知。在这里，我们鉴定出了CHALK10，它编码一种F-box蛋白，该蛋白负向调控水稻垩白。与野生型相比，chalk10突变体表现出异常的淀粉颗粒发育、淀粉含量降低以及淀粉理化性质的改变。CHALK10与赤霉素（GA）氧化酶SEMIDWARF-1（SD1）相互作用，并通过26S蛋白酶体途径促进SD1的泛素化和降解。过表达SD1的植株的谷粒垩白增加，将sd1突变体导入chalk10背景中很大程度上抑制了chalk10突变体中较高的垩白度。与野生型相比，chalk10突变体中的GA水平更高，施用生物活性GA形式GA会增加谷粒的垩白度。chalk10突变体中与淀粉降解或生物合成相关的基因表达发生改变，导致胚乳中淀粉产量减少和可代谢糖含量增加。总之，我们的研究结果揭示了一种调控垩白的新机制，并为改善水稻品质提供了潜在靶点。
