水稻黄绿叶突变体ygl11(t)的生理特性和基因克隆

Physiological Characterization and Gene Identification of a Yellow-Green Leaf Mutant ygl11(t) in Rice

在水稻品种南粳41中发现了一个黄绿叶自然突变体,经过多代连续自交形成了稳定的突变系,命名为ygl11（t）,ygl11（t）整个生育期叶片都表现为黄绿色。对苗期、分蘖盛期、齐穗期突变体和野生型的叶绿素含量进行测定,ygl11（t）的叶绿素含量是野生型的45.7%~74.7%,叶绿素a含量是野生型的55.2%~87.5%,叶绿素b含量是野生型的12.5%~25.3%,ygl11（t）的类胡萝卜素的含量是野生型的62.3%~97.0%。ygl11（t）在分蘖盛期的净光合速率显著高于野生型,花后10d,ygl11（t）的净光合速率比野生型略低。对突变体叶片中叶绿体的超微结构进行观察,发现突变体叶绿体内的类囊体基粒片层数目减少且严重扭曲变形。遗传分析表明,ygl11（t）叶色性状受1对隐性核基因控制。利用SSR分子标记将YGL11（t）初步定位在水稻第10染色体的长臂上,进一步利用新开发的InDel和CAPS标记将YGL11（t）定位在58.1kb的物理距离内。对该区段内存在的开放阅读框进行序列分析,发现突变体ygl11（t）中编码叶绿素a氧化酶（chlorophyll a oxygenase 1）基因（OsCAO 1）的第9个外显子存在2个碱基缺失,从而导致提前出现终止密码子,初步分析OsCAO1即为YGL11（t）的候选基因。

A spontaneous mutant showing yellow-green leaf throughout the growth period,designated as ygl11（t）,was screened and identified from rice cultivar Nanjing 41.This mutant was grown for several generations and showed stable mutation phenotype. The ygl11（t） mutant has reduced chlorophyll accumulation and abnormal chloroplast development.The average contents of total chlorophyll,chlorophyll a,chlorophyll b,and carotene in the ygl11（t）mutant were 45.7%to 74.7%,55.2% to 87.5%,12.5% to 25.3%,and 62.3% to 97.0% of these in wild type,respectively,at the stages of seedling,tillering and heading.The leaf net photosynthetic rate of the ygl11（t）was significantly higher at maximum tillering stage and slightly lower at 10 days after flowering than that of wild type.Ultrastructure analysis revealed that the grana lamellae of chloroplast thylakoid were less in number and abnormally developed in the ygl11（t）mutant.Genetic analysis suggested that the phenotype of ygl11（t）was controlled by a recessive nuclear gene.YGL11（t）was prelimarily mapped on the long arm of rice chromosome 10,and was finally narrowed to a 58.1kb region containing six open reading frames（ORFs）.All the six ORFs were amplified and sequenced.A 2-bp deletion was found in the 9th exon of the OsCAO1 gene,encoding a chlorophyll a oxygenase 1,which results in a premature stop codon and protein truncation in the ygl11（t）mutant.These results suggest that the OsCAO1 gene is the candidate of YGL11（t）.