水稻类病变突变体c5的遗传分析与目标基因的精细定位

水稻类病变突变体c5是由粳稻品种中花11种子经化学诱变剂EMS (甲基磺酸乙酯)诱变处理得到的。该突变体叶片在三叶期开始出现近似圆形褐色斑点,经DAB染色和台酚蓝染色显示这些斑点积累了过多的H₂O₂并引起程序性细胞死亡。与野生型相比,突变体c5的成熟期株高从110.4 cm减少到74.6 cm,有效分蘖数和每穗着粒数分别减少23.7%和28.5%,千粒重和结实率都显著降低,此外,c5还表现出对白叶枯病菌的广谱抗病性,对10个菲律宾生理小种都有强烈的抗性反应。遗传分析表明,c5的突变性状受单隐性核基因控制。利用c5和明恢86配组形成的包含6269个单株的F₂群体和18个分子标记,将c基因限定在水稻第5染色体长臂STS标记S41和S47之间大约102 kb的遗传距离内。序列分析发现该区间内其中有11个编码基因,且它们与现已报道的类病变基因都不同,暗示c5可能是一个新型类病变性状控制基因。

Genetic Analysis and Gene Fine Mapping of Rice Lesion Mimic Mutant c5

The lesion mimic mutant c5 was obtained bytreating the seeds of japonica variety Zhonghua 11 with chemical mutagen EMS (ethyl methane sulfonate). The phenotypes and main agronomic traits of the c5 mutant were investigated. There were many nearly circularbrown spots began to appear on c5 leaves at 3-leaf stage. These leaves were stained further with DAB and trypan blue respectively and indicated that there were excessive H₂O₂ production and clusters of dead cells in the lesion tissues. Compared with the wild-type, the height of c5 plant decreased from 110.4 cm to 74.6 cm, the number of effective tiller per plant and spikelet per panicle were reduced by 23.7% and 28.5% respectively, thousand-grain-weight and seed setting rate were significantly dropped.In addition, c5 is endowed a broad-spectrum resistance to bacterial blight resistance to ten Philippine races of X. oryzae pv. Oryzae (Xoo). Genetic analysis showed that the lesion mimic mutant c5 was controlled by a single recessive nuclear gene. Minghui86 was crossed with c5 and 6269 individuals of F₂ population and 18 pairs of molecular markers were used for gene mapping. And thegene was further mapping to rice chromosome 5 in a 102 kb region between STS markers S41 and S47. Sequence analysis of the 102 kb region revealed that there were 11 candidates for c5 gene. All the 11 candidate genes were different from those lesion mimic genes reported previously, which suggested that the phenotype of c5 may be controlled by a novel gene.