Petersen G, Seberg O
Botanical Institute, University of Copenhagen, Copenhagen, Denmark.
Mol Biol Evol. 2000 Nov;17(11):1589-96. doi: 10.1093/oxfordjournals.molbev.a026258.
The mode of transposition of miniature inverted-repeat transposable elements (MITEs) is unknown, but it has been suggested that they are duplicated rather than excised at transposition. However, the present investigation demonstrates that a particular family of MITEs, Stowaway:, is excised. Mapped onto a gene tree based on partial sequences of disrupted meiotic cDNA1 (DMC1) from 30 species of the Triticeae grasses, it is evident that at least two excisions have occurred, leaving short footprints. These footprints may subsequently be reduced in length or deleted. Excision of Stowaway: elements lends strong support to the suggestion that MITEs are DNA transposons and should be classified as class II elements. The evolution of Stowaway: elements can also be traced by scrutiny of the gene tree. It appears that base substitutions are as frequent in the conserved terminal inverted repeats (TIRs) as in the core of the element. Neither substitutions nor deletions lead to compensatory changes; hence, the highly stable secondary structure of the elements may gradually be reduced.
微型反向重复转座元件（MITEs）的转座模式尚不清楚，但有人提出它们在转座时是被复制而非切除。然而，目前的研究表明，一个特定的MITE家族，即“偷渡者”家族，是被切除的。根据来自30种小麦族禾本科植物的减数分裂cDNA1（DMC1）部分序列构建的基因树显示，很明显至少发生了两次切除事件，留下了短的足迹。这些足迹随后可能会缩短长度或被删除。“偷渡者”元件的切除有力地支持了MITEs是DNA转座子并应归类为II类元件的观点。“偷渡者”元件的进化也可以通过对基因树的仔细研究来追踪。似乎在保守的末端反向重复序列（TIRs）中碱基替换的频率与元件核心中的频率一样高。替换和缺失都不会导致补偿性变化；因此，元件高度稳定的二级结构可能会逐渐降低。
