Abstract:

Leaf, an crucial organ for photosynthesis, provides the basis of crop yield formation. In addition to a trait marker in breedings, leaf color mutants in crops are one of the prerequisites for investigation in chloroplast development and cultivation of new germplasms with higher photosynthetic efficiency. A yellow leaf mutant (yl1) were selected from a pool of Japonica rice Kitaake mutagenized with ethyl methanesulfonate(EMS). The yl1 mutant showed lower plant height, less grain number and less 1 000-grain weight compared with wild type. Genetic analysis showed that yellow leaf phenotype in yl1 mutant was caused by a single recessive gene. Map-based cloning demonstrated that the coding region of OsCAO1 (LOC_Os10g41780), encoding chlorophyllide a oxygenase, had a G to A point mutation site (Glycine 396 to Arginine in amino acid sequence) in yl1. Sequence analysis and GFP experiment indicated the mutation site G396R of CAO1 in yl1 is in catalytic domain, and made no change in CAO1 location in chloroplast. Therefore, G396 might be the key point for OsCAO1 enzyme activity as G396 was highly conserved in different species.

Key words: rice, yellow-green leaf mutant, CAO1, gene cloning, function

摘要：

叶片是植物进行光合作用的重要器官，是作物产量形成的基础。作物叶色突变体不仅是研究叶绿体发育机制、培育高光效新种质的前提，而且可以作为性状标记，应用于良种繁育及杂交育种。在经化学诱变剂甲基磺酸乙酯(EMS)处理的粳稻品种Kitaake突变体库中，筛选得到黄叶突变体yl1，yl1突变体的株高、穗粒数、千粒重与野生型相比均降低。遗传分析表明，yl1黄叶表型由单隐型基因控制，图位克隆表明yl1编码叶绿素酸酯a氧化酶(chlorophyllide a oxygenase,OsCAO1，LOC_ Os10g41780)基因发生点突变；yl1突变体OsCAO1突变位点位于催化功能域，没有改变其在叶绿体中的定位，且在不同物种之间高度保守，这表明该位点可能是OsCAO1的酶活关键氨基酸位点。

关键词: 水稻；黄叶突变体；叶绿素酸酯a氧化酶；基因克隆;功能