毛木耳rDNA序列结构及IGS鉴别菌种初探

Analyses of rDNA structure and preliminary evaluation of strains of Auricularia cornea based on IGS sequence

rDNA序列中的ITS作为DNAbarcode广泛应用于真菌的系统发育与物种辅助鉴定,IGS被认为可以用于种内水平不同菌株的鉴别。有关食用菌rDNA序列的报道较少。本研究对毛木耳Auricularia cornea单核菌株B02进行三代测序与组装,然后用二代测序数据进行校正,得到一个组装效果较好的基因组序列。比对Fibroporia vaillantiir的rDNA序列获得毛木耳rDNA重复单元的完整序列,每个重复单元包含ETS、18S rDNA、ITS1、5.8S rDNA、ITS2、28S rDNA、IGS1、5S rDNA和IGS2,长度分别为398bp、1790bp、156bp、156bp、206bp、3432bp、2247bp、121bp和2135bp,总长度10641bp,毛木耳rDNA有310个串联重复单元,转录组和系统发育分析均支持这一结果。与其他已报道的食用菌不同,毛木耳的IGS1、IGS2序列高度保守,其中IGS1的1400–2200bp区域在各拷贝之间没有多态性、而在品种之间有较高频率的SNP,这一片段序列有望用于品种鉴别研究。

ITS in rDNA sequences is widely used as a DNA barcode for phylogeny and auxiliary species identification of fungi,and IGS is used to identify different strains within-species level.There are rare reports on complete rDNA sequence in edible fungi.In this study,the third-generation sequencing of the Auricularia cornea mononuclear strain B02 were performed.The assembled sequencing data of the third-generation sequencing was corrected by the data of the next-generation sequencing,and a set of well assembled genome data was obtained.The complete sequence of the rDNA repeat unit was obtained by comparing rDNA sequence of Fibroporia vaillantii with that of A.cornea.Each repeat unit contained ETS,18 S rDNA,ITS1,5.8 S rDNA,ITS2,28 S rDNA,IGS1,5 S rDNA and IGS2,and the length was 398 bp,1790 bp,156 bp,156 bp,206 bp,3432 bp,2247 bp,121 bp and 2135 bp respectively,with a total length of 10641 bp.Both transcriptome and phylogenetic analysis supported this result.There were 310 tandem repeat units in the rDNA region.Unlike the other reported edible fungi,the IGS1 and IGS2 sequences of Auricularia cornea were highly conserved,and the 1400–2200 bp region of IGS1 had no polymorphism between strains,and there was a higher frequency of SNPs between strains.This IGS1 fragment is expected to identify varities of the fungus.