根據(jù)一份新的報(bào)告,，外來的遺傳成分通過水平轉(zhuǎn)移而不是傳統(tǒng)的遺傳從而把它們自己整合到了幾種哺乳類和爬行類物中的基因組中。
Cédric Feschotte及其同事發(fā)現(xiàn)了hAT (hobo/Activator/Tam3)轉(zhuǎn)座子超家族此前未歸類的成分，他們將其稱之為“太空侵略者”,。在大多數(shù)生物體內(nèi),，基因是從親代遺傳或者說傳遞給子代的。遺傳信息的橫向或者說水平轉(zhuǎn)移——這對(duì)于簡(jiǎn)單原核生物的進(jìn)化至關(guān)重要——發(fā)生在外來遺傳成分整合到宿主基因組中的時(shí)候,。這些成分通常是由病毒,、稱為質(zhì)粒的環(huán)狀DNA或者轉(zhuǎn)座子運(yùn)送的。轉(zhuǎn)座子是小片可轉(zhuǎn)移的DNA片斷,。
這組科學(xué)家在調(diào)查夜間活動(dòng)的靈長(zhǎng)類動(dòng)物——叢猴的DNA轉(zhuǎn)座子的時(shí)候發(fā)現(xiàn)了這些成分,，在經(jīng)過進(jìn)一步檢查之后，他們?cè)谄渌锓N中也發(fā)現(xiàn)了這些“侵略者”,，包括大鼠和小鼠,、負(fù)鼠和非洲爪蛙。然而,，其他許多脊椎動(dòng)物的基因組中并沒有“太空入侵者”,。這組作者說，這種入侵現(xiàn)象是科學(xué)家首次報(bào)告哺乳動(dòng)物中出現(xiàn)轉(zhuǎn)座子的水平轉(zhuǎn)移,，而且對(duì)受影響的物種的這種入侵很可能發(fā)生在大約1500萬年到4600萬年的類似時(shí)間段中,。（生物谷Bioon.com）
生物谷推薦原始出處：
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.
