Nurminsky D I, Moriyama E N, Lozovskaya E R, Hartl D L
Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts 02138, USA.
Mol Biol Evol. 1996 Jan;13(1):132-49. doi: 10.1093/oxfordjournals.molbev.a025551.
Drosophila virilis is a prominent reference species for comparison with Drosophila melanogaster in regard to patterns and mechanisms of molecular and genomic evolution. Sequences were determined for 11 Adh genes from 8 species of the D. virilis species group, including species from both the virilis phylad and the montana subphylad. The genome of D. virilis contains a 6-kb duplication that includes the entire Adh coding region. The pattern of sequence identity within the duplication strongly suggests a recent gene-conversion event bordered by 36-bp indels. As in other Drosophila, the amino-acid coding region of Adh is encoded by three exons interrupted by two short introns. The promoter region includes 16 blocks of sequence that are well conserved in D. virilis, Drosophila hydei, and D. melanogaster. The developmental profile of Adh transcription suggests a distal/proximal promoter switch analogous to that in D. melanogaster. Duplicate Adh genes were also found in Drosophila montana and Drosophila lacicola, which apparently originated independently of that in D. virilis. The Adh genes in all species of the D. virilis group have among the lowest codon bias of any Adh genes so far reported in the genus Drosophila. Taking the low codon bias into account, we estimate the time of divergence between the virilis and montana clades as 9.0 +/- 0.7 Mya and the approximate time of divergence of D. virilis from other members of the virilis phylad as 2.6 +/- 0.4 Mya. The region of the D. virilis genome containing Adh, as well as the chromosome as a whole, gives evidence of extensive rearrangements relative to the genome of D. melanogaster.
在分子和基因组进化的模式及机制方面，果蝇（Drosophila virilis）是与黑腹果蝇（Drosophila melanogaster）进行比较的重要参考物种。测定了果蝇属（D. virilis）物种组中8个物种的11个乙醇脱氢酶（Adh）基因的序列，其中包括来自virilis分支和montana亚分支的物种。果蝇（D. virilis）的基因组包含一个6 kb的重复序列，其中包括整个Adh编码区。重复序列内的序列同一性模式强烈表明最近发生了基因转换事件，其边界为36 bp的插入/缺失。与其他果蝇一样，Adh的氨基酸编码区由三个外显子编码，中间被两个短内含子打断。启动子区域包括16个在果蝇（D. virilis）、海德氏果蝇（Drosophila hydei）和黑腹果蝇（D. melanogaster）中高度保守的序列块。Adh转录的发育谱表明存在类似于黑腹果蝇的远端/近端启动子转换。在蒙塔纳果蝇（Drosophila montana）和拉西科拉果蝇（Drosophila lacicola）中也发现了重复的Adh基因，它们显然是独立于果蝇（D. virilis）中的Adh基因起源的。果蝇属（D. virilis）组所有物种中的Adh基因具有迄今为止在果蝇属中报道的所有Adh基因中最低的密码子偏好性。考虑到低密码子偏好性，我们估计virilis和montana分支之间的分歧时间为9.0±0.7百万年前，果蝇（D. virilis）与virilis分支其他成员的大致分歧时间为2.6±0.4百万年前。果蝇（D. virilis）基因组中包含Adh的区域以及整个染色体，相对于黑腹果蝇的基因组，显示出广泛重排的证据。
