一个水稻白化致死突变基因的精细定位和遗传研究

Genetic Analysis and Gene Mapping of an Albino Lethal Mutant in Rice

从粳稻品种日本晴经60 Co诱变的M1代材料中发现了一个白化致死突变体,该突变体从萌芽后一直表现白化,3叶期后逐渐衰亡。遗传分析表明,该突变表型受一对隐性核基因控制,将该白化突变体暂定名为al14。与野生型相比,al14突变体的叶绿素含量与类胡萝卜素含量显著降低。电子显微镜观察表明al14突变体不能形成完整的叶绿体,只有原片层体结构。对叶绿体编码基因的表达分析发现,突变体中光系统Ⅰ和光系统Ⅱ基因表达明显下调,核糖体结构基因和质体编码的RNA聚合酶亚基基因表达明显上调,但是PsbN(photosystemⅡprotein N)却上调表达水平最高,达到118.23倍。利用al14突变体与黄华占杂交获得的F2代分离群体进行基因定位,将该基因定位于水稻第6染色体上约40kb的范围。目前,该范围内没有叶色相关基因的报道,可能为一新的调控叶绿体发育的基因。

An albino lethal mutant,temporarily termed as al14(albino 14),was obtained from60 Coγ-ray radiated mutant pool of japonica rice variety Nipponbare.The mutant showed albino phenotype from germination,and died after 3-leaf stage.Genetic analysis revealed that the mutant phenotype was controlled by a single recessive nuclear gene.The chlorophyll and carotenoid contents in al14 declined dramatically.Transmission electron microscopy examination showed there were no obvious chloroplasts except prolamellar bodies in al14.The expression level of most genes of photosystemⅠand photosystem Ⅱdecreased dramatically,but the ribosomal genes and RNA polymerase genes in chloroplast increased notably in al14 mutant.In al14,the expression amount of PsbN,aphotosystem Ⅱ protein N gene,was 118.23 times as high as that in wild type.By genetic mapping with an F2 population generated by crossing the heterozygous al14 plants with indica variety Huanghuazhan,the al14 locus was mapped within 40 kb on chromosome6.So far there is no reported gene relative to leaf color,so it is a novel gene controlling chloroplast development.