一个水稻显性斑点叶突变体的鉴定和基因精细定位

通过EMS (ethane methyl sulfonate)诱变籼稻品种IR64获得一个稳定遗传的显性斑点叶突变体HM113。在大田环境下，突变体褐色斑点在播种后3周的叶片上产生，始穗期扩散至叶鞘。与野生型IR64相比，突变体HM113的株高、结实率和千粒重等农艺性状显著下降，光合色素含量、净光合速率和可溶性蛋白含量显著降低。同时突变体CAT和SOD活性显著降低，POD活性显著上升。组织化学分析显示，突变体叶片中积累了大量活性氧，且斑点处细胞坏死。白叶枯病菌接种结果显示，HM113是一个广谱抗性增强的突变体。实时定量PCR分析表明HM113中防卫反应基因AOS2、PAL4、PR10和PR1b等的表达大幅上调。遗传分析表明，突变体褐斑性状受单显性基因(Spl^HM113)控制，利用图位克隆法将该基因定位在第7染色体长臂RM21605和RM418之间，物理距离约为308 kb。本研究为褐斑基因Spl^HM113的克隆与功能分析奠定了基础。

Characterization and Gene Fine Mapping of a Rice Dominant Spotted-leaf Mutant

A stable inherited rice spotted-leaf mutant HM113 was isolated from an EMS-induced IR64 mutant bank. Under natural conditions, brown lesions were observed on the leaves in three weeks after sowing and spread to the sheaths at the initial heading stage. Agronomic traits including the plant height, panicle length, number of panicles, number of filled grain/panicle, seed-setting rate and 1000-grain weight were decreased significantly in HM113. In addition, the photosynthetic pigment contents, net photosynthetic rate and soluble protein content in the mutant were significantly lower than those in the wild type IR64, while the MDA content was similar to that in the wild-type. Activities of CAT and SOD were significantly lower and activity of POD was significantly higher in the mutant than in IR64. Histochemical analysis showed that cell death and ROS accumulation were occurred in and around the lesions in HM113. Furthermore, disease resistance to bacterial blight pathogens was significantly enhanced in the mutant in contrast to that in the wild type IR64. Expression of defense-related genes including AOS2, PAL4, PR10,and PR1b was apparently up-regulated in the mutant. Genetic analysis indicated that the mutant trait was controlled by a novel single dominant nuclear gene, tentatively termedas Spl^HM113, which was detected to be located in a region around 308 kb flanked by RM21605 and RM418 on the long arm of chromosome 7. The data and populations obtained in the present study would facilitate the isolation and functional analysis of Spl^HM113.