垩白严重影响稻米外观品质，与种子淀粉颗粒的发育相关。水稻垩白形成遗传机理的研究对于水稻品质改良意义重大。我们在日本晴的组培过程中发现了一份高垩白突变体chalk4，遗传分析和图位克隆表明高垩白受单隐性基因控制，因编码一个丙酮酸激酶基因功能丧失所致，定名为OsPK2。本项目在已有研究基础上，从基因互补、过表达、基因敲出、表达模式以及激酶活性等方面深入研究OsPK2基因的分子生物学功能，揭示其调控垩白的遗传机理，为水稻品质改良育种提供基因资源和理论依据。

Grain chalkiness is highly undesirable agronomic trait which related to starch granules development in the seed. The researches on genetic and molecular mechanisms of chalkiness formation are of great significance for quality improvement in rice breeding. Here, we isolated a mutant chalk4 (chalkiness4) from tissue culture of Nipponbare, which exhibited serious grain chalkiness in seeds. Genetic studies indicated that the mutant phenotypes were controlled by one recessive gene. The map-based cloning revealed that mutant phenotypes were caused by the mutation of an unreported gene OsPK2, encodes a private kinase. In this project, we will study the biology function of OsPK2 from the aspects of transgenic complementation, overexpression, gene pointed-knockout, expression pattern, private kinase activity et al. These results will lay a foundation for understanding the molecular mechanism how private kinase affects the chalkiness formation in rice and also provide gene resource and theoretical basis for improving rice yield and quality.