以稻曲病菌致病力丧失的突变菌株B1464为材料,对其生物学形态和分子遗传变异进行分析。B1464田间接种表现为不致病,与野生型菌株相比, 在营养贫瘠的MM培养基上生长速率没有显著差异,而在PSA和TB3培养基中生长速率较慢,并且在PS液体培养基中产孢能力下降,同时突变菌株的分生孢子与野生型相比形态和大小均发生变化。Southern杂交结果显示T-DNA在突变菌株B1464中以单拷贝形式插入,利用TAIL-PCR技术扩增得到的紧邻T-DNA两侧的侧翼序列在野生型中不相邻,与野生型菌株基因组比对发现突变菌株插入位点处丢失约20 kb的DNA片段。RT-PCR结果表明突变菌株中T-DNA插入位点两侧基因表达量均下调。推断突变菌株B1464的致病能力丧失可能是由于T-DNA的插入导致了染色体重排及破坏了某些基因的正常表达。

With an avirulent Ustilaginoidea virens strain B1464 as material,we analyzed the changes in biological morphology and pathogenic mechanism. Compared to the wild-type U. virens strain P1, the mutant strain B1464 showed no pathogenicity in the field. The rate of growth on MM medium was not different to P1 and B1464. On PSA and TB3 medium the rates of growth were nutritionally endowed. B1464 grew slower and produced few conidiophores in PS medium, and its conidiophores morphology and spore size became smaller. Genomic Southern bolt analysis confirmed that B1464 was single T-DNA insertional events. The flanking sequences of T-DNA obtained by TAIL-PCR were non-adjacent in the wild type. It was founds that the mutant strain lost about 20 kb sequences in the insertion site comparing with the wild type strain. The expression of the flanking genes of the T-DNA was down-regulated, detecting by semi-quantitative RT-PCR. The reason of the chromosome rearrangement and abnormal expression of some genes is the insertion of T-DNA, probably, leading to the mutant strain B1464 lost its pathogenicity.