水稻早衰突变体esl-H5的表型鉴定与基因定位

Phenotypic characterization and gene mapping of an early senescence leaf H5(esl-H5) mutant in rice(Oryza sativa L.)

在甲基磺酸乙酯(EMS)诱变粳稻淮稻5号的突变体库中,筛选到一个稳定遗传的叶片黄化早衰突变体esl-H5(early senescence leaf H5)。该突变体幼苗期表型正常,播种后50 d开始出现下部叶片黄化早衰表型。与野生型相比,esl-H5突变体抽穗期延迟,株高、穗长、穗粒数、有效分蘖数、千粒重等均显著降低,叶绿素含量显著减少。遗传分析表明该突变受一对隐性基因调控。分子标记定位结果显示,该突变基因定位于1号染色体。通过MutMap分析发现编码胼胝质合成酶基因Os01g0533000的最后一个外显子内有一个碱基G变成了A,这导致翻译提前终止。进化树分析结果显示, ESL-H5与拟南芥AtGSL7 (Glucan Synthase-Like 7)同源性最高。糖含量测定表明esl-H5突变体中可溶性糖和淀粉含量增高,推测ESL-H5功能缺失后影响了光合产物的转运,导致叶片中糖含量显著增高,进而引起叶片衰老。qRT-PCR结果显示, esl-H5突变体中抗病相关基因PR1a、PR1b、PR2、PR4、PR5和PR10表达量均高于野生型,这与突变体的白叶枯病抗性明显提高一致。上述研究结果为研究糖信号调控水稻衰老和抗病性奠定了基础。

A stable mutant esl-H5(early senescence leaf H5) was identified from the mutant library of japonica rice Huaidao 5population induced by ethyl methane sulfonate(EMS) treatment. The mutant was normal at seedling stage. However, the lower leaves in esl-H5 mutant displayed premature senescence at about 50 days after sowing. Compared with the wild type(WT), the heading date of the esl-H5 mutant was delayed, while agronomical traits including plant height, panicle length, grain number per panicle, effective tiller numbers, and 1000-grain weight were significantly reduced. Moreover, chlorophyll content was also decreased in esl-H5 mutant. Genetic analysis indicated that the early senescence trait in esl-H5 mutant was controlled by a single recessive gene. ESL-H5 gene was localized on chromosome 1 using molecular marker. MutMap analysis further revealed that one nucleotide G to A replace occurred in the last exon of Os01g0533000 gene which encodes callose synthase. The G to A replace in the ESL-H5 introduced a premature stop codon. Phylogenetic analysis showed that ESL-H5 was homology with Arabidopsis AtGSL7(Glucan Synthase-Like 7). At tillering stage, the contents of soluble sugar and starch were significantly increased in the leaves of the esl-H5 mutant compared with those of the WT. These results implied that the mutation of ESL-H5 affected the transport of photosynthetic products, resulting in premature leaf senescence phenotypes. The qRT-PCR analysis revealed that the expression levels of disease resistance-related genes PR1a, PR1b, PR2, PR4, PR5, and PR10 in esl-H5 mutant were higher than those in WT, which was consistent with the observation that esl-H5 mutant improved bacterial blight resistance. The present results lay the foundation for studying the roles of sugar signal in regulating rice senescence and disease resistance.