垩白是稻米胚乳中白色不透明部分, 为胚乳淀粉粒之间存在空隙而形成的一种光学特性。垩白的有无及大小是评价稻米品质的重要指标，该指标直接关乎稻米商品价值，也是影响我国主要稻区优质米生产的重要限制因素。然而，影响稻米垩白形成的因素是一个复杂的数量性状，受遗传因子与环境因素共同作用。因此，深入研究稻米垩白形成的分子生理机理，为培育垩白小而少的优质水稻新品种及水稻调优栽培提供理论基础，这对保障我国粮食安全具有十分重要的意义。在前期研究中，申请人利用EMS诱变获得高垩白米率的突变体ossfc1，除垩白存在显著差异外，该突变体的其它农艺性状与野生型对照无显著差异。利用图位克隆技术证实OsSFC1就是控制突变体ossfc1稻米垩白形成的基因，该基因编码线粒体载体家族蛋白。本项目将在前期的研究基础上，研究OsSFC1基因、ROS与琥珀酸代谢、温氮与稻米垩白之间的关系，揭示其调控稻米垩白形成的分子生理机理。

Grain chalk is an opaque part in the rice endosperm, which is an optical character caused by the air-gap of loose arrangement between proteinoplast and amyloplast. Thus, chalkiness is a very important indicator of the appearance quality for rice, and this indicator is directly related to the value of rice commodity and is also an important limiting factor affecting development of high-quality grain in many rice-producing areas of China. However, the chalkiness is a complex quantitative trait that is controlled by many genes and is readily influenced by environmental factors, especially heat stress and nitrogen. Therefore, clarification of the heredity of chalkiness and its molecular mechanisms is of important significance to reduce the chalkiness, improve the appearance quality and the commercial value of rice, which is of great significance to ensure food security in China. In the previous our study, the mutant ossfc1 with high chalkiness rate was isolated from Zhehui7954 through EMS mutagenesis. Except for the significant difference in chalkiness, the other agronomic traits of the mutant were not significantly different from wild type. Using map-based cloning approach, we determined that a G-to-T substitution in the OsSFC1 gene encoding a mitochondrial carrier family protein underlies the phenotype of high chalkiness rate in the ossfc1 mutant. Based on the previous research, this project will study the relationship between OsSFC1 gene, metabolism of ROS and succinate, temperature and nitrogen, and chalkiness. These results would be used to reveal its molecular and physiological mechanism on regulation of rice grain chalkiness.