水稻叶片淀粉积累及早衰突变体esl9的鉴定与基因定位

Identification and Gene Mapping of Starch Accumulation and Early Senescence Leaf Mutant esl9 in Rice

利用EMS诱变籼型三系保持系西农1B,获得了一个新的水稻叶片淀粉过度积累而导致的早衰突变体esl9(early senescence leaf 9)。该突变体苗期叶片呈淡绿色,分蘖期开始除心叶外的叶片从叶尖开始黄化衰老,逐渐延伸至叶中上部,基部保持绿色,该性状一直持续到成熟。与野生型相比,esl9叶片光合色素含量下降,O_2^-、·OH和H_2O_2等活性氧含量上升,保护酶系统中SOD和CAT活性降低。组织化学分析表明,esl9叶片中积累了大量的淀粉颗粒,淀粉含量显著上升;qRT-PCR结果显示,淀粉合成途径相关基因上调,磷酸丙糖(TP)分配途径基因下调,推测基因突变可能改变了TP的分配途径,导致叶片过度积累淀粉,破坏叶绿体结构,光合系统受阻,活性氧增多,引起叶片黄化衰老。遗传分析表明该突变体受一对显性核基因调控,ESL9位于第11染色体标记S11-110与S11-87之间,物理距离为304.9 kb,这为进一步基因克隆和功能研究奠定了基础。

A new leaf senescence mutant esl9（early senescence leaf 9） was discovered from the progeny of indica maintainer line 1B mutated by ethyl methane sulfonate（EMS）. Compared with the wild-type, the leaf of esl9 was pale green at seedling stage; chlorosis occurred at leaf tip and gradually extended to the middle-upper parts of leaf at tillering stage. However, the leaf base remained green until maturity. In the esl9, the photosynthetic pigment contents declined, and the contents of reactive oxygen species（ROS）, such as O2？, ·OH, and H2O2, heightened compared with those in the wild-type. At the same time, activities of protective enzymes, SOD and CAT, both reduced in esl9. The results of iodine-iodide kalium dyeing and starch content determination showed that more starch granules accumulated in the esl9 leaf. Quantitative RT-PCR results indicated that genes responsible for starch synthesis were up-regulated and genes participated in the triose phosphate distribution path were down-regulated. We made an inference that gene mutation changed the distribution of triose phosphate, resulting in starch granules accumulating in the leaf, chloroplast structure being destroyed and photosynthetic system being blocked, thus increasing the contents of ROS, eventually causing leaf senescence. Genetic analysis demonstrated that the phenotype of esl9 was controlled by a dominant nuclear gene. The target gene ESL9 was mapped between SSR markers S11-110 and S11-87 with a physical distance of 304.9 kb on chromosome 11. These results will lay a foundation for cloning and functionally analysing ESL9.