National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural University, Wuhan, China.
Shanghai Agrobiological Gene Center, Shanghai, China.
Nat Genet. 2014 Apr;46(4):398-404. doi: 10.1038/ng.2923. Epub 2014 Mar 16.
Grain chalkiness is a highly undesirable quality trait in the marketing and consumption of rice grain. However, the molecular basis of this trait is poorly understood. Here we show that a major quantitative trait locus (QTL), Chalk5, influences grain chalkiness, which also affects head rice yield and many other quality traits. Chalk5 encodes a vacuolar H(+)-translocating pyrophosphatase (V-PPase) with inorganic pyrophosphate (PPi) hydrolysis and H(+)-translocation activity. Elevated expression of Chalk5 increases the chalkiness of the endosperm, putatively by disturbing the pH homeostasis of the endomembrane trafficking system in developing seeds, which affects the biogenesis of protein bodies and is coupled with a great increase in small vesicle-like structures, thus forming air spaces among endosperm storage substances and resulting in chalky grain. Our results indicate that two consensus nucleotide polymorphisms in the Chalk5 promoter in rice varieties might partly account for the differences in Chalk5 mRNA levels that contribute to natural variation in grain chalkiness.
垩白度是稻米在市场销售和食用过程中极不受欢迎的一个品质性状。然而，该性状的分子基础仍不清楚。本研究显示一个主要的数量性状位点（QTL）Chalk5 影响垩白度，同时也影响整精米率和许多其他品质性状。Chalk5 编码液泡 H(+)-焦磷酸酶（V-PPase），具有无机焦磷酸（PPi）水解和 H(+)-转运活性。Chalk5 的高表达增加了垩白度，推测是通过扰乱发育种子中内膜运输系统的 pH 动态平衡，影响蛋白体的生物发生，并与大量小泡状结构的增加耦合，从而在胚乳贮藏物质之间形成气腔，导致垩白粒。我们的结果表明，水稻品种中 Chalk5 启动子的两个核苷酸多态性共识可能部分解释了 Chalk5 mRNA 水平的差异，导致了垩白度的自然变异。
