中文摘要：

微型反向重复转座元件（MITEs）是一种非自主性DNA类转座子。从四川省雅安市野外的金凤蝶（Papiliomachaon Linnaeus）中分离到-株微孢子虫，简称PM-1。采用生物信息学分析方法，利用MITE—Hunter软件在PM．1基因组中鉴定出21个MITEs家族，命名为NpmMEl-NpmME21。其中有5个家族属于Stowaway—like类，1个家族属于Tourist-like类，2个家族属于Pegasus—like类，其余13个家族为新家族。比较家蚕微孢子虫（Nosema bombycis）已鉴定的MITEs转座子，发现PM-1分离株的NpmME20与家蚕微孢子虫的NbMEI属于同一家族，且在家蚕微孢子虫基因组中的拷贝数是PM-1分离株基因组中的30倍，表明该MITEs家族从2种微孢子虫共同祖先分化后，在家蚕微孢子虫基因组中经历了爆发式的扩增。对PM．1分离株NpmMEs各家族内拷贝序列两两间遗传距离的分析显示，NpmME1、NpmME8家族的遗传距离明显大于NpmME10、NpmME13、NpmME16家族，在家蚕微孢子虫中也有类似现象，暗示着前两者更为古老。进一步调查NpmMEs在PM．1基因组上的位置发现，NpmMEs转座子偏向于分布在基因侧翼非编码区，无基因内插入偏向；部分NpmMEs序列与基因起始密码子或终止密码子重叠，改变了基因的原有结构。研究结果有助于进一步阐释微孢子虫MITEs转座子的进化起源以及对基因组结构的影响。

英文摘要：

Miniature inverted-repeat transposable elements （MITEs） are non-autonomous elements of DNA transposons. A microsporidian strain named PM-1 was isolated from field insect Papilio machaon Linnaeus in Ya＇an, Sichuan Province. The software MITE-Hunter was applied to search MITEs from PM-1 genome by bioinformatic analysis. As a result, 21 families of MITEs were characterized and named NpmME1 - NpmME21. Five of them belong to Stowaway-like family, one belongs to Tourist-like family, two belong to Pegasus-like family, and the rest thirteen are of completely novel families. By comparison with MITEs transposons identified from Nosema bombycis, PM-1 Npm-ME20 belongs to the same family as N. bombycis NbME1. Moreover, the copy number of it in N. bombycis was up to 30 times higher than that in PM-1, indicating that this MITE family might have undergone a burst expansion in N. bombycis genome after species divergence. The pairwise distance within each family was calculated, and the results showed that genetic distance of NpmME1 and NpmME8 was obviously farther than that of NpmME10, NpmME13 and NpmME16. Such genetic relationship was also observed in N. bombycis, suggesting that the first two families appear to be more ancestral. Further investigation of NpmMEs locations showed that NpmMEs preferentially inserted into flanking regions rather than into coding regions of genes in the genome of PM-1. Some NpmMEs overlap with the start codon or the stop codon of genes, leading to an alternation of original structure of those genes. These results would facilitate further investigation on evolutionary origin of microsporidian MITEs and their impact on genomic structure.