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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 mutant of early senescence (esl9) caused by the excessive accumulation of starch in rice leaves was obtained by using EMS to mutate indica three - line maintainer line. The leaves of these mutants were light green at the seedling stage. At beginning of tillering stage, the leaves except the heart leaves started to yellow and aged, then gradually extended to the upper part of the leaves and remained green at the base. The traits lasted until maturity. Compared with the wild type, the photosynthetic pigment content of esl9 decreased, the content of reactive oxygen species such as O 2 -, · OH and H 2 O 2 increased, and the activity of SOD and CAT in the protective enzyme system decreased. Histochemical analysis showed that a large amount of starch granules were accumulated in esl9 leaves and the content of starch increased significantly. The results of qRT-PCR showed that the genes related to starch synthesis pathway were up-regulated and the gene of triphosphate pathway was down-regulated. TP distribution pathway, leading to excessive accumulation of starch leaves, damage to chloroplast structure, photosynthetic system blocked, reactive oxygen species increased, causing leaf yellow aging. Genetic analysis showed that the mutant was regulated by a pair of dominant nuclear genes. ESL9 was located between chromosomes S11-110 and S11-87 on chromosome 11 with a physical distance of 304.9 kb, which laid the foundation for further gene cloning and functional studies.