白粉菌交配型位点基因结构及分子系统学关系

白粉菌是一类植物专性寄生真菌,广泛分布于世界各地,可引起多种植物白粉病。开展白粉菌交配型基因研究可以为全面认识白粉菌的生活史循环和系统演化提供证据。本研究以子囊菌中已报道的10种MAT基因和4种侧翼基因的氨基酸序列为种子序列,采用生物信息学方法在21个白粉菌基因组中进行氨基酸同源性分析,探索MAT基因及其侧翼基因的种类和线性排布。结果表明,21个白粉菌基因组中有10个属于MAT1-1型,包含MAT1-1-1和MAT1-1-3两种基因;10个属于MAT1-2型,仅包含MAT1-2-1基因;在Erysiphe pulchra的基因组中同时存在MAT1-1-1、MAT1-1-3、MAT1-2-1;而4种侧翼基因SLA2、APC5、APN2和CoxVia在21个白粉菌基因组中均存在。21个菌株中有两个菌株Blumeria graminis f. sp. hordei RACE1和Golovinomyces orontii的MAT基因和4种侧翼基因分布在同一个scaffold,其余菌株MAT基因和侧翼基因均不在同一scaffold出现。本研究分别分析了具有MAT1-1和MAT1-2的菌株中MAT基因和4种侧翼基因的排列关系,同时根据9个菌株的MAT基因注释信息,推测了其他菌株的MAT基因结构。结果表明,同属白粉菌的MAT基因结构相同,属间MAT基因结构差异明显。以从白粉菌基因组中获得的MAT1-1-1、MAT1-1-3和MAT1-2-1 3种MAT基因序列分别构建系统发育树,发现布氏白粉菌属Blumeria、白粉菌属Erysiphe和戈洛文白粉菌属Golovinomyces分别形成独立分枝,且白粉菌属与戈洛文白粉菌属形成姊妹群,这与前人对白粉菌系统发育关系的研究结果一致。本研究得到的白粉菌MAT基因种类、分布及其结构的相关结果为进一步实验提供了理论依据,为探究白粉菌的系统发育提供了新的思路。

Structure and phylogeny analyses of the mating-type loci in powdery mildews

Powdery mildews are obligate parasitic Ascomycetes, which cause powdery mildew diseases on a wide range of plants and distribute all over the world. Studies on the mating-type (MAT) genes in powdery mildews would be helpful for understanding life cycle and phylogenetic evolution of the fungi. The amino acid sequences encoded by ten MAT genes and four flanking genes from different ascomycetes were used as seeds to search high similarity sequences from the whole genome sequences of twenty-one powdery mildew isolates. The results showed that ten isolates belonging to MAT1-1 type only include MAT1-1-1 and MAT1-1-3 genes and ten isolates belonging to MAT1-2 type only contain MAT1-2-1 gene. The three mating genes, MAT1-1-1, MAT1-1-3, and MAT1-2-1, were all identified in Erysiphe pulchra. The flanking genes SLA2, APN2, CoxVia, and APC5 were detected in all genomes. The conserved MAT genes and their flanking genes are present in the same scaffold of two species, Blumeria graminis f. sp. hordei RACE1 and Golovinomyces orontii, while they are not present in the same scaffold in the other examined isolates. The structure of MAT loci was also predicted based on the annotation information from nine species. The results showed that MAT gene structure was conserved in the same genus but varied between different genera. The phylogenetic trees were constructed with MAT1-1-1, MAT1-2-1, and MAT1-1-3 gene sequences, and the results showed that Blumeria, Erysiphe, and Golovinomyces were clustered in a distinct clade whereas Erysiphe and Golovinomyces grouped as sister lineages, which were coincided to the phylogenetic relationships of these genera in the previous studies. The results of this study may provide information for mating type genes research and provide a new idea of phylogenetic analyses in powdery mildews.