通过⁶⁰Co-γ辐射诱变籼稻中恢8015获得了一个在全生育期叶片均呈黄绿色的突变体w390。与野生型相比,突变体中检测不到叶绿素b的存在,且叶绿素a和类胡萝卜素的含量分别降低了50.6%和44.8%;主要农艺性状调查结果显示,突变体的株高、单株有效穗数、每穗总粒数、每穗实粒数较野生型分别降低了12.0%、22.3%、18.5%和27.6%;透射电镜结果显示:突变体的类囊体数量明显减少,基粒垛叠方向异常;遗传分析表明该突变性状受一对隐性核基因控制。利用突变体与粳稻日本晴杂交构建的F₂群体,将突变基因定位至水稻第10染色体长臂约71.8 kb的区域内。对该区间包含的15个ORFs进行序列分析,发现突变体中编码叶绿素酸酯氧化酶1(chlorophyllide a oxygenase 1)的基因OsCAO1的第8外显子发生了两个单碱基突变,导致第394和396位的亮氨酸和甘氨酸分别突变为组氨酸和谷氨酸,推测该突变基因是一个OsCAO1功能丧失的新等位基因。

A yellow-green leaf mutant, designated as w390, was isolated from the progeny of ⁶⁰Co-γ-treated indica cultivar R8015. The mutant exhibited a stable yellow-green leaf phenotype during the whole life cycle. The chlorophyll b was not detected in w390, and the chlorophyll a and carotenoids contents of w390 were reduced by 50.6% and 44.8%, compared with the wild-type. The plant height, the number of panicle per plant, the number of spikelets per panicle, the number of grains per panicle of w390 were reduced by 12.0%, 22.3%,18.5% and 27.6%, respectively. The transmission electron microscope assay demonstrated that the number of thylakoids decreased and granas were poorly stacked in the mutant, resulting in underdevelopment of chloroplasts. Genetic analysis showed that the yellow-green leaf phenotype was controlled by a single recessive gene. Using an F₂ mapping population derived from the cross of w390 mutant and Nipponbare, the gene was delimitated to a region of 71.8-kb on the long arm of chromosome 10, which contained 15 ORFs. Sequence analysis revealed that the mutant carried two nucleotide substitutions in the eighth exon of OsCAO1 gene, which led to the substitution of leucine and glycine for histidine and glutamic acid, respectively. This implied that W390 might be a novel allele of OsCAO1 gene.