美國(guó)舊金山州立大學(xué)生物學(xué)助理教授卡倫-克勞表示：“我們的研究發(fā)現(xiàn)匙吻鱘擁有自身基因組的副本,。這種復(fù)制形成了額外的基因材料,，提高了比較研究的復(fù)雜性。這可能改變我們針對(duì)肢體發(fā)育的研究方式,。”為了研究人類的肢體如何發(fā)育,，科學(xué)家將老鼠的肢體基因與魚類的鰭基因進(jìn)行比較。此前有關(guān)匙吻鱘的研究顯示,，這種魚類在出現(xiàn)四足動(dòng)物前很久就擁有生長(zhǎng)出肢體所需要的“基因包”,。四足動(dòng)物最后進(jìn)化成爬行類、鳥類,、兩棲類和哺乳動(dòng)物,。
研究中，克勞和同事對(duì)美洲匙吻鱘含有19個(gè)Hox基因的染色體片段進(jìn)行了排序,。Hox基因決定體形和肢體發(fā)育,，同時(shí)也是幫助科學(xué)發(fā)現(xiàn)整個(gè)基因族副本的主要指示器。完整基因組副本被研究人員稱之為進(jìn)化史上“一個(gè)顛覆游戲規(guī)則的事件”,，讓一種物種出現(xiàn)新種或者奇特種群創(chuàng)造了條件,。
這種復(fù)制的出現(xiàn)是一系列看似不可能的條件同時(shí)滿足的結(jié)果，讓匙吻鱘的每一個(gè)基因都擁有副本,。完成復(fù)制后,，基因?qū)χ械囊粋€(gè)基因保持原有的功能,，另一個(gè)要么消失，要么擁有一個(gè)新功能,?？藙诒硎荆?ldquo;額外的基因材料為進(jìn)化提供了畫布，讓進(jìn)化過(guò)程描繪出各種景象,。”克勞一直從事新奇物種和生物多樣性研究。
科學(xué)家認(rèn)為這種基因組復(fù)制在有頜類脊椎動(dòng)物出現(xiàn)前就已發(fā)生,。在進(jìn)化樹的特定枝杈(譜系)也出現(xiàn)完整基因組復(fù)制現(xiàn)象,，植物要比動(dòng)物更為普遍?？藙谡f(shuō)：“我們對(duì)匙吻鱘進(jìn)行的研究顯示動(dòng)物的完整基因組復(fù)制現(xiàn)象并沒(méi)有此前認(rèn)為的那么罕見(jiàn),。”（生物谷Bioon.com）
doi: 10.1093/gbe/evs067
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An independent genome duplication inferred from Hox paralogs in the American paddlefish-a representative basal ray-finned fish and important comparative reference
Karen D. Crow, Christopher D. Smith, Jan-Fang Cheng, Günter P. Wagner and Chris T. Amemiya
Vertebrates have experienced two rounds of whole genome duplication in the stem lineages of deep nodes within the group, and a subsequent duplication event in the stem lineage of the teleosts-a highly diverse group of ray-finned fishes. Here we present the first full Hox gene sequences for any member of the Acipenseriformes, the American paddlefish, and confirm that an independent whole genome duplication occurred in the paddlefish lineage, approximately 42 million years ago based on sequences spanning the entire HoxA cluster and eight genes on the HoxD gene cluster. These clusters comprise different HOX loci, and maintain conserved synteny relative to bichir, zebrafish, stickleback and pufferfish, as well as human, mouse, and chick. We also provide a gene genealogy for the duplicated fzd8 gene in paddlefish and present evidence for the first Hox14 gene in any ray-finned fish. Taken together, these data demonstrate that the American paddlefish has an independently duplicated genome. Substitution patterns of the “beta” paralogs on both the HoxA and HoxD gene clusters suggest transcriptional inactivation-consistent with functional diploidization. Further, there are similarities in the pattern of sequence divergence among duplicated Hox genes in paddlefish and teleost lineages, even though they occurred independently approximately 200 million years apart. We highlight implications on comparative analyses in the study of the “fin-limb transition” as well as gene and genome duplication in bony fishes, which includes all ray-finned fishes as well as the lobe-finned fishes and tetrapod vertebrates.
