水平基因轉(zhuǎn)移（horizontal gene transfer，HGT）,，是相對(duì)于垂直基因傳遞（親代傳遞給子代）的另一種遺傳物質(zhì)傳遞方式,，是物種進(jìn)化和基因組革新的重要驅(qū)動(dòng)力之一,。水平基因轉(zhuǎn)移現(xiàn)象在原核生物及單細(xì)胞真核生物中比較常見(jiàn),，然而，在多細(xì)胞的動(dòng)物中鮮有報(bào)道,，更不知該機(jī)制對(duì)動(dòng)物的進(jìn)化有著怎樣的影響,。
在中國(guó)科學(xué)院昆明動(dòng)物研究所文建凡研究員和美國(guó)東卡羅萊納大學(xué)黃錦苓副教授的共同指導(dǎo)下，碩士研究生倪婷通過(guò)全基因組篩選,、系統(tǒng)發(fā)生分析和結(jié)構(gòu)域分析等方法,，首先在較為低等的動(dòng)物玻璃海鞘（Ciona intestinalis）基因組中鑒定出了92個(gè)來(lái)自多種藻類的基因，它們隸屬于14個(gè)基因家族,。進(jìn)一步的調(diào)查驚人地發(fā)現(xiàn),，原來(lái)這些基因普遍存在于不同動(dòng)物的基因組中。這表明這些基因最有可能是在動(dòng)物的共同祖先階段就已經(jīng)獲得,。又因這些基因來(lái)源于多種不同藻類,，因而不太可能是因特定藻類的內(nèi)共生而轉(zhuǎn)移來(lái)的，更可能是動(dòng)物祖先以多種藻類為食所致,。該情形很可能正如著名的進(jìn)化生物學(xué)家Doolittle W.F.（1998）所言：you are what you eat,！對(duì)這些基因的功能分析結(jié)果表明，它們主要與分子轉(zhuǎn)運(yùn),、細(xì)胞調(diào)控及甲基化信號(hào)等功能密切相關(guān),，提示著這些基因的獲得可能有助于動(dòng)物祖先中細(xì)胞間的交流從而影響著動(dòng)物的多細(xì)胞化（multicellularity）這一重要的進(jìn)化進(jìn)程。總之,，該研究不僅首次發(fā)現(xiàn)了動(dòng)物基因組中普遍存在不少早期通過(guò)水平基因轉(zhuǎn)移獲得的外源基因,，而且表明該事件可能對(duì)整個(gè)動(dòng)物界的進(jìn)化產(chǎn)生重要的影響。此外,，該研究還為“無(wú)質(zhì)體真核生物中的藻類基因并不都起源于原始質(zhì)體”的論斷提供了額外的證據(jù),。該研究成果近期已在“BMC Evolutionary Biology”（DOI 10.1186/1471-2148-12-83）上發(fā)表。
本工作得到了國(guó)家自然科學(xué)基金項(xiàng)目和中國(guó)科學(xué)院知識(shí)創(chuàng)新工程重要方向項(xiàng)目的資助,。（生物谷Bioon.com）
doi:10.1186/1471-2148-12-83
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Ancient gene transfer from algae to animals: Mechanisms and evolutionary significance
Ting Ni, Jipei Yue, Guiling Sun, Yong Zou, Jianfan Wen and Jinling Huang
Background Horizontal gene transfer (HGT) is traditionally considered to be rare in multicellular eukaryotes such as animals. Recently, many genes of miscellaneous algal origins were discovered in choanoflagellates. Considering that choanoflagellates are the existing closest relatives of animals, we speculated that ancient HGT might have occurred in the unicellular ancestor of animals and affected the long-term evolution of animals. Results Through genome screening, phylogenetic and domain analyses, we identified 14 gene families, including 92 genes, in the tunicate Ciona intestinalis that are likely derived from miscellaneous photosynthetic eukaryotes. Almost all of these gene families are distributed in diverse animals, suggesting that they were mostly acquired by the common ancestor of animals. Their miscellaneous origins also suggest that these genes are not derived from a particular algal endosymbiont. In addition, most genes identified in our analyses are functionally related to molecule transport, cellular regulation and methylation signaling, suggesting that the acquisition of these genes might have facilitated the intercellular communication in the ancestral animal. Conclusions Our findings provide additional evidence that algal genes in aplastidic eukaryotes are not exclusively derived from historical plastids and thus important for interpreting the evolution of eukaryotic photosynthesis. Most importantly, our data represent the first evidence that more anciently acquired genes might exist in animals and that ancient HGT events have played an important role in animal evolution.
