rDNA-ITS序列分析在真菌鉴定中的应用

Application of rDNA ITS sequence analysis in fungus identification

目的:通过对3株真菌的rDNA-ITS序列进行分析,以探讨、说明基于核糖体RNA基因(即rDNA)内转录间隔区(Internal Transcribed Spacer,ITS)的多态性的序列分析(rDNA-ITS序列分析)在真菌鉴定中的应用。方法:通过PCR扩增与测序的方法测得待检真菌菌株的rDNA-ITS序列,从GENBANK获取相似序列,使用BLAST和DNAMAN工具对rDNA-ITS序列进行比对分析。结果:1号真菌菌株与Xylariales sp.LM40(属炭角菌目)同源性高,但尚不能鉴定到具体的属、种;2号真菌菌株可鉴定到种,为草酸青霉Penicillium oxalicum;3号真菌菌株可鉴定到种内组水平,为近平滑假丝酵母III组(最新命名为Candida metapsilosis)。结论:相对于传统的真菌形态学鉴定方法,rDNA-ITS序列分析用于真菌鉴定更客观、省时、简便、快速,但目前也存在一定的应用限制(受基因库的完善程度、高度同源性序列的多少以及具体物种ITS区的可变程度等影响)并不能鉴定出所有真菌,宜与传统的形态学鉴定方法相结合用于真菌鉴定。

Objective：To introduce and illuminate the application of rDNA ITS sequence analysis in fungus identification on basis of sequence and length polymorphisms of internal transcribed spacer（ITS） in ribosomal RNA gene（rDNA）.Methods：The three pending fungus strains′ rDNA ITS sequences tested by PCR amplification and sequencing methods were analyzed and compared with similar sequences from GENBANK by NCBI BLAST online tool and DNAMAN software.Results：No.1 fungus strain had a high homology with Xylariales sp.LM40,but was not yet identifiable on genus or species level of taxonomic classification.No.2 strain was identified as Penicillium oxalicum,a genus level.No.3 strain was identified as Candida metapsilosis,new designation of Candida parapsilosis group Ⅲ,a group level in species relatively.Conclusion：Compared with the traditional morphological identification methods,the rDNA ITS sequence analysis is more objective,time-saving,convenient,and fast for fungus identification,but with some applied limits currently.Depended on the perfection degree of gene database,the number of high-degree homology sequence,the variability extent of ITS region of biological individuals and so on it can be applied.Then,it does not identify all fungi,and should be combined with the traditional morphological identification methods for fungus identification.