人气管普孢子虫基因组中MITEs转座子的鉴定及进化分析

Characterization and Genomic Evolution of MITEs in Microsporidian Trachipleistophora hominis

利用生物信息学方法,首次在人气管普孢子虫（Trachipleistophora hominis）基因组内鉴定到9个MITEs家族ThME1ThME9,共123个拷贝,MITEs转座子的长度均小于600bp。根据靶位点重复序列（Target site duplication,TSD）的不同,将ThME1归属于Tc1/Mariner超家族,ThME2和ThME3归属于PIF/Harbinger超家族,ThME5和ThME6归属于CACTA超家族（超家族的名字用正体较好,下同）,其余家族归为新家族。分析发现,人气管普孢子虫中的所有MITEs家族的吉布斯自由能均小于0,表明MITEs家族具有形成二级结构的潜能,有利于该家族在基因组上转座。人气管普孢子虫MITEs家族在基因组的插入时间估计在0-800万年内,而且这种插入在基因组中是随机的,没有位置偏向性,并发现2个MITEs转座子拷贝插入到基因编码区内部。上述结果为进一步研究微孢子虫MITEs转座子的起源以及功能奠定了基础。

Up to now,there was still no report of MITEs in the microsporidia species except for the Nosemaspecies.Nine MITEs family,designated as ThME1-ThME9in this study,were firstly identified in Trachipleistophora hominis genome by means of computer methods.As a consequence,a total of 123 MITEs copies derived from these families were targeted and the length of them was less than 600 bp.According to the feature of TSD,ThME1 was attributed to Tc1/Mariner superfamily,ThME2 and ThME3were attributed to PIF/Harbinger superfamily,ThME5 and ThME6were attributed to CACTA superfamily,and the rest were defined as unknown.The analysis of sequence structure showed that the free energy of all MITEs families in T.hominis genome was less than 0,indicating that MITEs family should have the potential to form secondary structures and benefit to its transposition.The evolution time of MITEs insertion in the genome was estimated to be no more than 8million years.No bias distributions were found for the MITEs in the genome of T.hominis,two of which were inserted into the protein-coding region,which may have affect on the gene structure.Our results laid the foundation to further study the origin and the function of MITEs transposons in microsporidia species.