Bettencourt B R, Feder M E
Department of Organismal Biology and Anatomy, University of Chicago, Illinois 60637, USA.
Mol Biol Evol. 2001 Jul;18(7):1272-82. doi: 10.1093/oxfordjournals.molbev.a003912.
To determine how the modern copy number (5) of hsp70 genes in Drosophila melanogaster evolved, we localized the duplication events that created the genes in the phylogeny of the melanogaster group, examined D. melanogaster genomic sequence to investigate the mechanisms of duplication, and analyzed the hsp70 gene sequences of Drosophila orena and Drosophila mauritiana. The initial two-to-four hsp70 duplication occurred 10--15 MYA, according to fixed in situ hybridization to polytene chromosomes, before the origin and divergence of the melanogaster and five other species subgroups of the melanogaster group. Analysis of more than 30 kb of flanking sequence surrounding the hsp70 gene clusters suggested that this duplication was likely a retrotransposition. For the melanogaster subgroup, Southern hybridization and an hsp70 restriction map confirmed the conserved number (4) and arrangement of hsp70 genes in the seven species other than D. melanogaster. Drosophila melanogaster is unique; tandem duplication and gene conversion at the derived cluster yielded a fifth hsp70 gene. The four D. orena hsp70 genes are highly similar and concertedly evolving. In contrast, the D. mauritiana hsp70 genes are divergent, and many alleles are nonfunctional. The proliferation, concerted evolution, and maintenance of functionality in the D. melanogaster hsp70 genes is consistent with the action of natural selection in this species.
为了确定黑腹果蝇中hsp70基因的现代拷贝数（5个）是如何进化的，我们在黑腹果蝇种群的系统发育中定位了产生这些基因的复制事件，检查了黑腹果蝇的基因组序列以研究复制机制，并分析了奥氏果蝇和毛里求斯果蝇的hsp70基因序列。根据对多线染色体的原位杂交定位，最初的两到四个hsp70基因复制事件发生在1000万至1500万年前，早于黑腹果蝇种群的起源以及黑腹果蝇与其他五个物种亚群的分化。对hsp70基因簇周围超过30 kb的侧翼序列分析表明，这种复制可能是逆转座。对于黑腹果蝇亚群，Southern杂交和hsp70限制性图谱证实了除黑腹果蝇外的其他七个物种中hsp70基因的数量（4个）和排列是保守的。黑腹果蝇是独特的；在衍生的基因簇处发生串联重复和基因转换产生了第五个hsp70基因。奥氏果蝇的四个hsp70基因高度相似且协同进化。相比之下，毛里求斯果蝇的hsp70基因是分化的，许多等位基因没有功能。黑腹果蝇hsp70基因的增殖、协同进化和功能维持与该物种中自然选择的作用是一致的。
