水稻早衰突变体esl2的遗传分析和基因定位

利用EMS诱变水稻籼型恢复系缙恢10号, 从其后代中鉴定出一个早衰突变体esl2, 苗期正常, 孕穗期开始叶尖和叶缘黄化衰老。与野生型相比, 孕穗期和抽穗期光合色素含量均显著下降, 抽穗期倒一叶的超氧化酶歧化酶(SOD)活性、可溶性蛋白(SP)含量降低, 活性氧(ROS)、过氧化物酶(POD)、过氧化氢酶(CAT)、丙二醛(MDA)和脯氨酸(PRO)含量或活性增加。超微结构观察表明, esl2衰老部位的细胞多中空且形状不规则, 伴随细胞裂解、细胞质溶解等特征; 同时, 叶绿体结构异常, 叶绿体膜溶解、基粒模糊, 基质片层疏松, 类囊体发育异常。遗传分析表明, 该突变体受一对隐性核基因调控。利用1 005株西农1A/esl2的F₂隐性定位群体, 最终将Esl2定位在第4染色体SSR标记RM17122和swu4-13之间, 物理距离约244 kb, 这为Esl2基因的克隆和功能研究奠定了基础。

Genetic Analysis and Gene Mapping of Early Senescence Leaf Mutant esl2 in Rice

An early senescence leaf mutant temporarily designated as esl2 was discovered in the progeny of an excellent indica restorer line Jinhui 10 with seeds treated by ethyl methane sulfonate(EMS).The mutant kept normal at seedling stage and showed etiolated senescence leaves from booting sage to the maturity,especially at tip and margin of leaf blade.By contrast with the wild type,photosynthetic pigment contents decreased significantly at both booting stage and heading stage,superoxide dismutase(SOD) activity and soluble protein contents decreased significantly,while the activities of peroxidase(POD) and catalase(CAT),and contents of reactive oxygen species(ROS),malondialdehyde(MDA) and praline increased significantly at heading stage in the esl2 mutant.The assay of Transmission Electronic Microscope(TEM) observation was performed and demonstrated that the most cells appeared irregular and void with endolysis and disrupted organelles at senescence part of the mutational leaf,concomitantly,abnormal chloroplast appeared and showed dissolved membrane,indistinct grana,disorganized lamellar structure and incorrect thylakoid.Genetic analysis suggested that the mutational trait was controlled by one nuclear recessive gene.Xinong 1A was crossed with the esl2 and 1 005 mutational F2 single plants were used for gene mapping.Finally,Esl2 locus was mapped between SSR marker RM17122 and swu4-13 on the chromosome 4 with physical distance of 244 kb.This result provides a foundation of Esl2 gene cloning by map-based strategy as well as its functional analysis.