一个水稻黄绿叶突变体ygl10的遗传分析和基因定位

以籼稻93-11为背景的水稻突变体中发现一个黄绿叶突变体(yellow-green leaf,ygl10)。形态分析表明,与野生型93-11相比,ygl10突变体株高、穗长降低,结实率下降。叶绿素含量测定表明,ygl10突变体中叶绿素a、叶绿素b和类胡萝卜素含量均极显著降低,其中叶绿素b降幅最大,只有野生型的2%。叶绿体超微结构观察表明,突变体中类囊体和基粒片层数量明显减少。遗传分析结果表明,该黄绿叶突变体由一隐性核基因控制。进一步利用分子标记将ygl10定位在水稻第10染色体约380kb的区段内。对该区段内存在的ORF进行序列分析,发现编码叶绿素a氧化酶(chlorophyll a oxygenase)基因(OsCAO1)的第9个外显子存在5个碱基缺失,从而导致提前出现终止密码子,推测CAO1即为ygl10的候选基因。

Genetic Analysis and Position Cloning of a yellow green leaf 10 (ygl10) Gene,Responsible for Leaf Color in Rice

A rice mutant characterized by yellow green leaves (named as ygl10) was obtained from an indica cultivar 93 11 via radiation of 60Co γ ray. Morphological analysis showed that, the ygl10 mutant exhibited shorter plant height and panicle length, decreased seed setting rate compared to its wild type (93 11). Moreover, the chlorophyll content in the ygl10 mutant leaves dramatically decreased, especially for chlorophyll b content, being only about 2% of that in  its wild type. In addition, the SEM results showed that the numbers of grana lamella, and thylakoids in the mutant were less than those in the wild type. Genetic analysis and gene mapping showed that the yellow green leaf mutant was controlled by a single recessive gene, which  was located  in a 380 kb region on chromosome 10. We further analyzed the putative candidate open reading frames in the target region through sequencing, and the results showed that there was a 5 nucleotide deletion in the ninth exon of CAO1 gene (encoding chlorophyll a  oxygenase involved in the biosynthesis of chlorophyll b), resulting in the frame shift to generate a new premature stop codon. Therefore, it is deduced that CAO1 is the candidate of ygl10.