水稻类病斑早衰突变体lmps1的表型鉴定与基因定位

经甲基磺酸乙酯(EMS)诱变优良籼型水稻恢复系缙恢10号,获得一个稳定遗传的水稻类病斑早衰突变体lmps1(lesion mimic and premature senescence 1)。该突变体苗期表型正常,分蘖早期出现褐色类病斑,且斑点数目随植株生长而增多,孕穗期叶片开始萎黄衰老。与野生型相比,突变体lmps1的每穗总粒数下降8%(P0.05),株高、穗长、有效穗数、每穗实粒数、结实率以及千粒重分别下降14.3%、24.3%、27.2%、50%、45.7%与14.5%,差异均达极显著水平(P0.01)。遮光处理表明,突变体lmps1的类病斑性状受光照诱导。孕穗期叶片光合色素含量下降且光合效率降低, H2O2含量增加,抗氧化酶SOD和CAT的活性显著降低。透射电镜观察结果显示,突变体lmps1叶肉细胞中叶绿体数目减少,叶绿体的类囊体片层结构损伤降解。qRT-PCR结果显示,突变体lmps1中防卫反应相关基因除POX22.3表达量降低外,POC1、PAL、PBZ1、PR1、NPR1、PR5表达量均极显著高于野生型。遗传分析表明突变体lmps1的类病斑早衰性状受1对隐性核基因控制,利用西农1A与突变体lmps1杂交所得F2群体中的突变株,将目标基因定位于第7染色体长臂端粒附近约167.3 kb的物理区段内。

Phenotypic characterizing and gene mapping of a lesion mimic and premature senescence 1 (lmps1) mutant in rice (Oryza sativa L.)

An elite rice indica restorer line, Jinhui 10 was chemically mutated with ethyl methane sulfonate (EMS). A novel and stable mutant, lesion mimic and premature senescence 1 (lmps1) was identified from the descendant library. The growth and development of lmps1 plant was normal at seedling stage, but its leaves began to exhibit brown spots at the beginning of tillering stage, and the number of the spots increased as the plant growing up. When mutant plant entered booting stage, leaves started to wilt and became yellowish, then exhibited premature senescence. Compared with wild type, grains per panicle of lmps1 decreased by 8%, significantly lower than that of wild type (P < 0.05). Besides, plant height, panicle length, effective panicle number, filled grain number per panicle, seed setting rate, and 1000-grain weight of lmps1 correspondingly decreasedly 14.3%, 24.3%, 27.2%, 50.0%, 45.7%, and 14.5%, statistically lower than those of wild type (P < 0.01). The shading treatment suggested that the mutant performance of lmps1 was light induced. Within the cells of lmps1, both of photosynthetic pigment content and photosynthetic efficiency decreased. At the same time, H₂O₂ content increased, and activities of protective enzymes, SOD and CAT, reduced in lmps1. The observation by transmission electronic microscope (TEM) demonstrated that chloroplast number reduced in lmps1, and the chloroplast thylakoid lamellar structure seriously damaged and degraded. As a result of qRT-PCR, the expression levels of POC1, PAL, PBZ1, PR1, NPR1, and PR5 were higher in lmps1 than in wild type, while that of POX22.3 was lower than that of wild type. The genetic analysis indicated that the lesion mimic and premature senescence of lmps1 was under the control of a recessive nuclear gene. Mapping result via F₂ population derived from the cross between Xinong 1A and lmps1 showed that, the target gene was located in a 167.3 kb physical interval near the telomere of the long arm of chromosome 7 in rice (Oryza sativa L.).