Maruyama K, Hartl D L
Department of Genetics, Washington University School of Medicine, St. Louis, MO 63110-1095.
J Mol Evol. 1991 Dec;33(6):514-24. doi: 10.1007/BF02102804.
The transposable element mariner occurs widely in the melanogaster species group of Drosophila. However, in drosophilids outside of the melanogaster species group, sequences showing strong DNA hybridization with mariner are found only in the genus Zaprionus. The mariner sequence obtained from Zaprionus tuberculatus is 97% identical with that from Drosophila mauritiana, a member of the melanogaster species subgroup, whereas a mariner sequence isolated from Drosophila tsacasi is only 92% identical with that from D. mauritiana. Because D. tsacasi is much more closely related to D. mauritiana than is Zaprionus, the presence of mariner in Zaprionus may result from horizontal transfer. In order to confirm lack of a close phylogenetic relationship between the genus Zaprionus and the melanogaster species group, we compared the alcohol dehydrogenase (Adh) sequences among these species. The results show that the coding region of Adh is only 82% identical between Z. tuberculatus and D. mauritiana, as compared with 90% identical between D. tsacasi and D. mauritiana. Furthermore, the mariner gene phylogeny obtained by maximum likelihood and maximum parsimony analyses is discordant with the species phylogeny estimated by using the Adh genes. The only inconsistency in the mariner gene phylogeny is in the placement of the Zaprionus mariner sequence, which clusters with mariner from Drosophila teissieri and Drosophila yakuba in the melanogaster species subgroup. These results strongly suggest horizontal transfer.
转座因子水手座在果蝇的黑腹果蝇物种组中广泛存在。然而，在黑腹果蝇物种组之外的果蝇中，仅在扎普里果蝇属中发现了与水手座具有强烈DNA杂交信号的序列。从瘤突扎普里果蝇获得的水手座序列与黑腹果蝇亚组的成员毛里求斯果蝇的序列有97%的同一性，而从塔卡西果蝇分离出的水手座序列与毛里求斯果蝇的序列只有92%的同一性。由于塔卡西果蝇与毛里求斯果蝇的亲缘关系比扎普里果蝇与毛里求斯果蝇的亲缘关系近得多，扎普里果蝇中水手座的存在可能是水平转移的结果。为了证实扎普里果蝇属与黑腹果蝇物种组之间缺乏密切的系统发育关系，我们比较了这些物种之间的乙醇脱氢酶（Adh）序列。结果表明，瘤突扎普里果蝇和毛里求斯果蝇之间Adh的编码区只有82%的同一性，而塔卡西果蝇和毛里求斯果蝇之间为90%的同一性。此外，通过最大似然法和最大简约法分析得到的水手座基因系统发育与使用Adh基因估计的物种系统发育不一致。水手座基因系统发育中唯一的不一致之处在于扎普里果蝇水手座序列的位置，它与黑腹果蝇亚组中的泰斯ieri果蝇和雅库巴果蝇的水手座序列聚类。这些结果有力地表明了水平转移。
