根据一份新的报告，外来的遗传成分通过水平转移而不是传统的遗传从而把它们自己整合到了几种哺乳类和爬行类物中的基因组中。
Cédric Feschotte及其同事发现了hAT (hobo/Activator/Tam3)转座子超家族此前未归类的成分，他们将其称之为“太空侵略者”。在大多数生物体内，基因是从亲代遗传或者说传递给子代的。遗传信息的横向或者说水平转移——这对于简单原核生物的进化至关重要——发生在外来遗传成分整合到宿主基因组中的时候。这些成分通常是由病毒、称为质粒的环状DNA或者转座子运送的。转座子是小片可转移的DNA片断。
这组科学家在调查夜间活动的灵长类动物——丛猴的DNA转座子的时候发现了这些成分，在经过进一步检查之后，他们在其他物种中也发现了这些“侵略者”，包括大鼠和小鼠、负鼠和非洲爪蛙。然而，其他许多脊椎动物的基因组中并没有“太空入侵者”。这组作者说，这种入侵现象是科学家首次报告哺乳动物中出现转座子的水平转移，而且对受影响的物种的这种入侵很可能发生在大约1500万年到4600万年的类似时间段中。（生物谷Bioon.com）
生物谷推荐原始出处：
PNAS October 20, 2008, doi: 10.1073/pnas.0806548105
Repeated horizontal transfer of a DNA transposon in mammals and other tetrapods
John K. Pace II, Clément Gilbert, Marlena S. Clark, and Cédric Feschotte
Horizontal transfer (HT) is central to the evolution of prokaryotic species. Selfish and mobile genetic elements, such as phages, plasmids, and transposons, are the primary vehicles for HT among prokaryotes. In multicellular eukaryotes, the prevalence and evolutionary significance of HT remain unclear. Here, we identified a set of DNA transposon families dubbed SPACE INVADERS (or SPIN) whose consensus sequences are ≈96% identical over their entire length (2.9 kb) in the genomes of murine rodents (rat/mouse), bushbaby (prosimian primate), little brown bat (laurasiatherian), tenrec (afrotherian), opossum (marsupial), and two non-mammalian tetrapods (anole lizard and African clawed frog). In contrast,SPIN elements were undetectable in other species represented in the sequence databases, including 19 other mammals with draft whole-genome assemblies. This patchy distribution, coupled with the extreme level of SPIN identity in widely divergent tetrapods and the overall lack of selective constraint acting on these elements, is incompatible with vertical inheritance, but strongly indicative of multiple horizontal introductions. We show that these germline infiltrations likely occurred around the same evolutionary time (15–46 mya) and spawned some of the largest bursts of DNA transposon activity ever recorded in any species lineage (nearly 100,000 SPIN copies per haploid genome in tenrec). The process also led to the emergence of a new gene in the murine lineage derived from a SPINtransposase. In summary, HT of DNA transposons has contributed significantly to shaping and diversifying the genomes of multiple mammalian and tetrapod species.
