通过EMS诱变获得遗传稳定的水稻褐色颖壳突变体(brown hull 6, 简称bh6)。与野生型IR64相比,在自然条件下突变体的颖壳颜色自抽穗期开始逐渐加深直至蜡熟期颖壳呈深褐色,除千粒重和穗长显著降低外,其他农艺性状(株高、每株有效穗数、每穗实粒数、结实率)未发生显著改变。遗传分析表明,该褐色颖壳性状受一对隐性核基因控制。构建突变体bh6与正常色颖壳水稻CPSLO17的F₂分离群体作为基因定位群体,将该基因精细定位在第9染色体长臂上106 kb的区段内。序列分析发现,突变体中F-box蛋白基因OsFBX310 (LOC_Os09g12150)编码区第1013位碱基由G突变为A,致使其所编码的蛋白序列第338位的甘氨酸(Gly)突变成天冬氨酸(Asp)。通过构建OsFBX310功能互补载体进行转化试验,结果表明,突变体转基因植株的谷壳颜色恢复为正常颜色。该基因是已报道的水稻OsFBX310基因的新等位基因,命名为OsFBX310^bh6。OsFBX310^bh6及其野生型等位基因的克隆对深入研究338位甘氨酸/天冬氨酸在类黄酮代谢过程中的作用,以及丰富水稻特异种质资源具有积极意义。

A brown hull 6 (bh6) mutant of rice was isolated from an EMS-induced IR64 mutant bank. The brown pigments start to accumulate in the hulls after heading and reach a maximum level in mature seeds. The 1000-grain weight and panicle length of bh6 significantly decreased while other agronomic traits including plant height, number of productive panicles per plant, number of filled grains per panicle and seed-setting rate were largely similar to those of the wild-type IR64. Analysis of pigment contents indicated that the levels of total flavonoids and anthocyanin in bh6 were significantly increased. The brown hull phenotype was controlled by a single recessive gene on the long arm of chromosome 9. Sequencing analysis indicated that a single base substitution (G-A) at position 1013 was detected in the candidate gene (LOC_Os09g12150) encoding an F-box domain containing protein. Functional complementation using the wild-type allele could rescue the mutation. The mutation, designated as OsFBX310^bh6, is a new allele of OsFBX310 functioning as an inhibitor of brown hull. Isolation of OsFBX310^bh6 provides useful experimental materials and would facilitate the studies on mechanism of flavonoid metabolism in monocot plants.