水稻条纹叶和白穗基因SLWP的定位及变异分析

Mapping and Mutation Analysis of Stripe Leaf and White Panicle Gene SLWP in Rice

【目的】对叶绿体发育相关基因进行克隆和功能分析,为解析叶绿体功能奠定分子基础。【方法】用甲基磺酸乙酯(EMS)处理籼稻9311获得一个条纹叶和白穗突变体slwp,通过色素分析和农艺性状观察分析该突变体的表型,通过图位克隆方法分离该基因,进一步利用定量PCR分析相关基因的表达情况。【结果】突变体slwp从2叶期开始至抽穗期表现出条纹叶表型,抽穗后幼穗白化,光合色素含量明显低于野生型;株高降低、抽穗延迟、产量降低等表型。该突变性状为单隐性核基因控制,该基因定位于水稻第6染色体短臂C6-4和N14标记之间0.91Mb区间内。基因组测序表明核糖核苷二磷酸还原酶小亚基基因(RNRS1)编码区第776位点发生单碱基替换,导致甘氨酸突变为天冬氨酸;该基因与已报导的水稻基因St1、Gws和St-wp为等位基因。通过对这4个等位基因的突变位点和表型进行分析,总结了该基因不同位点突变对植株表型的影响以及籼粳之间的差异。表达分析显示与叶绿素合成有关的基因受到不同程度调控,叶绿体发育第一和第二阶段基因上调表达,光合作用相关基因均下调表达。【结论】本研究分析了SLWP(RNRS1)基因不同位点的变异对水稻表型的影响,相关结果加深了对RNRS1基因功能的认识,有助于阐明叶绿体发育的分子机制。

【Objective】Cloning and function analysis of chloroplast development-associated genes will lay a molecular basis for clarifying chloroplast function. 【Method】A stripe leaf and white panicle mutant, slwp, was isolated from an ethylmethylsulfone（EMS） mutagenic population of indica rice cultivar 9311. The phenotypic characteristics of slwp were analyzed by pigments determination and agronomic traits observation. The SLWP gene was identified by map-based cloning method. The gene expression was analyzed by the quantitative real-time PCR.【Result】The slwp mutant showed stripe leaf phenotype from two-leaf stage to heading and white panicle after heading accompanied by obviously decreased pigment contents compared with wild type. The slwp mutant was also featured with delayed heading and decreased plant height and yield and so on. Genetic analysis demonstrated that the mutant phenotype was controlled by a recessive nuclear gene. The SLWP gene was fine-mapped to a 0.91 Mb interval between markers C6-4 and N14 on the short arm of rice chromosome 6. Sequence comparison displayed that a single nucleotide substitution（G776 A） in the coding region of ribonucleoside-diphosphate reductase small chain（RNRS1）, which led to the amino acid change from Gly to Asp. The SLWP was allelic to St1, Gws and St-wp. We analyzed the mutant sites and phenotypes of the four alleles and summarized the effect of mutation on plant phenotypes and the difference between indica and japonica. In addition, expression analysis revealed that genes involved in chlorophyll biosynthesis were differently regulated, genes involved in the first and second steps of chloroplast differentiation were up-regulated, and genes involved in photosynthesis were down-regulated. 【Conclusion】We analyzed the effect of mutant sites in SLWP（RNRS1） gene on rice phenotypes. It deepens understanding for RNRS1 function and help to elucidate the molecular mechanism of chloroplast development.