南方灵芝ITS、EF1-α和RPB2序列多态性研究

内转录间隔区（ITS）、延伸因子1-α（EF1-α）与RNA聚合酶II第二大亚基（RPB2）是真菌系统学研究中常用的基因片段。已有研究发现,在同一个体内ITS也可能存在差异,但EF1-α和RPB2是否也存在同样的现象却鲜有报道。本研究通过克隆测序,分析了南方灵芝Ganoderma australe的ITS、EF1-α和RPB2在同一个体中的序列差异,并探讨这种序列差异是否会影响分子鉴定的准确性。结果表明,在南方灵芝供试样品中,ITS、EF1-α和RPB2序列都有可能存在个体内变异,但个体内变异程度不尽相同。基于供试样品和克隆测序结果发现,ITS序列在同一个体内的变异最高可达2.3%,而RPB2序列在同一个体内的差异仅0.5%,EF1-α序列在同一个体内序列差异也可高达1.8%。ITS和EF1-α序列在同一个体内的差异可能超过了灵芝属部分物种间的差异,对于部分灵芝属物种来说直接利用克隆序列进行分子鉴定或系统发育分析可能存在一些问题。

Intragenomic polymorphisms of the ITS,EF1-α and RPB2 sequences of Ganoderma australe

The internal transcribed spacer (ITS), translation elongation factor 1-α (EF1-α) and second largest subunit of RNA polymerase II (RPB2) are commonly used for taxonomic or phylogenetic studies of fungi. Intragenomic variation of ITS has been detected in many fungal groups but few cases on EF1-α and RPB2 have been reported. In this study, the intragenomic variation of ITS, EF1-α and RPB2 in Ganoderma australe was detected using PCR cloning to determine whether intragenomic variation affects accuracy of molecular identification. The results showed that intragenomic variation of ITS, EF1-α and RPB2 was present in different specimens and their heterogeneity level was different. Heterogeneity level of the same gene also varied between individuals. Based on the examined samples and cloned sequences, the intragenomic variation of ITS was up to 2.3%, while that of RPB2 only 0.5%. Intragenomic variation of EF1-α could reach 1.8%. The highest intragenomic variation of ITS and EF1-α might exceed the interspecific difference, and therefore the use of these sequences for phylogenetic analyses and molecular identification of Ganoderma species could be problematic.