A family of Tc1/mariner transposons with a characteristic DD38E triad of catalytic amino acid residues, named Intruder (IT), was previously discovered in sturgeon genomes, but their evolutionary landscapes remain largely unknown. Here, we comprehensively investigated the evolutionary profiles of ITs, and evaluated their cut-and-paste activities in cells. ITs exhibited a narrow taxonomic distribution pattern in the animal kingdom, with invasions into two invertebrate phyla (Arthropoda and Cnidaria) and three vertebrate lineages (Actinopterygii, Agnatha, and Anura): very similar to that of the DD36E/IC family. Some animal orders and species seem to be more hospitable to Tc1/mariner transposons, one order of Amphibia and seven Actinopterygian orders are the most common orders with horizontal transfer events and have been invaded by all four families (DD38E/IT, DD35E/TR, DD36E/IC and DD37E/TRT) of Tc1/mariner transposons, and eight Actinopterygii species were identified as the major hosts of these families. Intact ITs have a total length of 1.5–1.7 kb containing a transposase gene flanked by terminal inverted repeats (TIRs). The phylogenetic tree and sequence identity showed that IT transposases were most closely related to DD34E/Tc1. ITs have been involved in multiple events of horizontal transfer in vertebrates and have invaded most lineages recently (< 5 million years ago) based on insertion age analysis. Accordingly, ITs presented high average sequence identity (86–95%) across most vertebrate species, suggesting that some are putatively active. ITs can transpose in human HeLa cells, and the transposition efficiency of consensus TIRs was higher than that of the TIRs of natural isolates. We conclude that DD38E/IT originated from DD34E/Tc1 and can be detected in two invertebrate phyla (Arthropoda and Cnidaria), and in three vertebrate lineages (Actinopterygii, Agnatha and Anura). IT has experienced multiple HT events in animals, dominated by recent amplifications in most species and has high identity among vertebrate taxa. Our reconstructed IT transposon vector designed according to the sequence from the “cat” genome showed high cut-and-paste activity. The data suggest that IT has been acquired recently and is active in many species. This study is meaningful for understanding the evolution of the Tc1/mariner superfamily members and their hosts.

中文翻译：

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入侵者（DD38E），是动物中最近进化的DD34E / Tc1转座子的同胞家族

先前在in鱼基因组中发现了具有特征性DD38E三联催化氨基酸残基的Tc1 / mariner转座子家族，名为Intruder（IT），但其进化前景仍然未知。在这里，我们全面研究了IT的进化概况，并评估了它们在细胞中的剪切和粘贴活性。IT在动物界显示出狭窄的分类学分布模式，侵入了两个无脊椎动物门（节肢动物和猪唇草）和三个脊椎动物世系（放线in，Agnatha和Anura）：与DD36E / IC家族非常相似。Tc1 / mariner转座子似乎对某些动物纲和物种更友好，Tc1 / mariner转座子的四个家族（DD38E / IT，DD35E / TR，DD36E / IC和DD37E / TRT）已经入侵了两栖动物中的一个订单和七个放线翅目订单，这是最常见的水平转移事件。放线opter科物种被确定为这些科的主要寄主。完整的IT全长为1.5–1.7 kb，其中包含一个转座酶基因，该基因侧接末端反向重复序列（TIR）。系统进化树和序列同一性表明，IT转座酶与DD34E / Tc1最为相关。IT参与了脊椎动物中水平转移的多种事件，并根据插入年龄分析，最近（小于500万年前）入侵了大多数血统。因此，IT在大多数脊椎动物物种中均表现出较高的平均序列同一性（86–95％），提示某些人活跃。ITs可以在人类HeLa细胞中转座，共有TIR的转座效率高于天然分离株的TIR。我们得出的结论是，DD38E / IT源自DD34E / Tc1，可以在两个无脊椎动物门（节肢动物和猪唇草）以及三个脊椎动物谱系（放线opter，Agnatha和阿努拉）中检测到。IT在动物中经历了多次HT事件，主要由大多数物种的最近扩增引起，并且在脊椎动物类群中具有很高的地位。根据“猫”基因组序列设计的重组IT转座子载体表现出很高的剪切和粘贴活性。数据表明，IT技术已被最近收购，并且在许多物种中都很活跃。这项研究对于了解Tc1 / mariner超家族成员及其寄主的进化意义重大。