水稻温敏型叶片白化转绿突变体tsa2的表型鉴定与基因定位

水稻温敏型叶色突变体是研究植物光合作用、叶绿体结构和功能以及温度影响叶绿体发育的理想材料。利用甲基磺酸乙酯(EMS)诱变籼型水稻(OryzasativaL.)三系保持系西农1B,从其后代中筛选到一个突变性状稳定遗传的温敏型叶片白化转绿突变体tsa2 (temperature-sensitive green-revertible albino 2)。与野生型相比, tsa2突变表型受温度影响, 22°C条件下萌发的野生型幼苗表型正常,而tsa2幼苗完全白化,且约40%白化苗死亡,存活白化苗的光合色素含量、光合速率均显著降低,成熟期主要农艺性状均显著变劣;在28°C下萌发的tsa2幼苗叶片呈浅绿色并伴有白条纹,其光合色素含量显著降低,光合速率及主要农艺性状差异较小; 32°C下萌发的tsa2幼苗叶片无明显差异。透射电镜观察显示,与野生型相比,tsa2在22°C下叶肉细胞中无叶绿体或存在异常发育叶绿体(尚未分化出基粒和基层),在28°C下部分叶肉细胞含少量发育完整的叶绿体,在32°C下叶肉细胞数量及形态均正常。实时荧光定量PCR(qRT-PCR)分析表明,与野生型相比,tsa2突变体中部分光合色素代谢途径基因、叶绿体发育相关基因及光合作用相关基因的表达水平呈不同程度变化。遗传分析表明, tsa2突变表型受一对隐性核基因控制, TSA2被定位于第5染色体SSR标记S5-57和S5-119之间,物理距离为718 kb。本研究为水稻遗传改良及研究温度影响叶绿体发育机制奠定了基础。

Phenotypic identification and gene mapping of temperature-sensitive green- revertible albino mutant tsa2 in rice (Oryza sativa L.)

Temperature-sensitive leaf color mutants of rice are ideal materials in studies on photosynthesis, chloroplast structure and function, and chloroplast development. A temperature-sensitive green-revertible albino mutant (tsa2) with genetically stable mutational traits was screened out from the progeny of ethyl methane sulfonate (EMS) treated indica three-line maintainer line Xinong 1B. The wild type seedlings had normal phenotype at 22°C, while the mutant tsa2 had completely albino leaves and about 40% of albino seedlings died at the seedling stage; the photosynthetic pigment contents and photosynthetic rate of surviving albino seedlings decreased significantly, and the main agronomic traits were significantly lower than those of the wild type at maturity stage. When germinated at 28°C, tsa2 showed light-green leaves with white streaks and significantly lower photosynthetic pigment contents than the wild type, while a small difference of photosynthetic rate and main agronomic traits between the tsa2 and the wild type. No significant difference in leaves was observed between tsa2 and the wild type when seedlings germinated at 32°C. Transmission electron microscope observation revealed that the albino leaves of tsa2 demonstrated abnormal chloroplast development (without differentiated grana and granum lamella) or without chloroplast at 22°C and completely developed chloroplasts in partial mesophyll cells at 28°C, and normal number and morphology of mesophyll cells compared with wild type at 32°C. The analysis of qRT-PCR indicated that genes related to partial photosynthetic pigment metabolism pathways, chloroplast development and photosynthesis expressed in tsa2 to a varying degrees compared with these of the wild type. Genetic analysis suggested that mutational phenotype of tsa2 was controlled by a single recessive nuclear gene, TSA2, which was finally mapped between SSR markers S5-57 and S5-119 on chromosome 5, with a physical distance of 718 kb. These results lay a foundation for the research on genetic improvement and the mechanism explanation of chloroplast development affected by temperature in rice (Oryza sativa L.).