茶树菇复合群菌株内ITS序列异源特征分析

Sequence Characterization of Intrastrain ITS Heterogeneity in Cyclocybe aegerita Species Complex

ITS序列作为常用的分子标记,广泛应用于真菌系统学研究,然而在茶树菇类群分析中缺乏综合分析。结果表明:对茶树菇菌株ITS序列进行测序,从中发现了8个菌株ITS测序图谱存在套峰。各菌株分离的子代同核体群体中存在2种ITS序列类型,推测亲本由不同ITS类型同核体杂交而成。从混杂的ITS扩增产物里进行克隆测序后,发现ITS1和ITS2区域存在模板复制转换的现象。依据ITS和线粒体小亚基mtSSU构建的聚类树显示的拓扑结构不一致,部分来自于同一菌株的ITS序列聚类到不同的群中。因此,茶树菇的ITS序列显示出多样性且组成复杂,从ITS杂合菌株中直接进行克隆分析会产生不正确的序列信息,给菌株鉴定和系统分析造成错误的结果。

ITS sequences are commonly used molecular markers and are widely used in fungal phylogeny.However,there is a lack of comprehensive analysis on groups of Cyclocybe aegerita.The findings indicated that Intra-strain ITS heterogeneity with positional double peaks was identified in 8 strains,and each of them contained two types of ITS sequences based on the sequence analysis of monokaryons,suggesting these heterozygotes probably produced by the cross of monokaryons from different groups.Cloning of ITS products from heterozygotes produced some chimeric sequences,and the template switching occurs in ITS1 and ITS2 regions.All strains in phylogenetic tree constructed by mtSSU and ITS sequences,but the topology structure of them was not accordant.Additionally,heterogous ITS derived from the same strain showed obvious divergence even falling in different groups.Our study showed the diversity and complexity of the C.aegerita strains,and it suggests the direct sequencing of ITS products from heterozygotes probably produce wrong result on the strain identification and phylogenetic analysis of the C.aegerita species complex.