Kwiatowski J, Skarecky D, Burgos M, Ayala F J
Department of Ecology and Evolutionary Biology, University of California, Irvine 92717.
Insect Mol Biol. 1992;1(1):3-13. doi: 10.1111/j.1365-2583.1993.tb00072.x.
We have cloned and sequenced the Cu, Zn superoxide dismutase gene of Chymomyza amoena. The coding sequence has the same length as in Drosophila species and in Ceratitis capitata. There are two introns, located at the same sites as in Ceratitis. The second intron is absent in Drosophila: this places Chymomyza outside the Drosophila lineage, contrary to proposals based on anatomical and other evidence. The nucleotide or amino acid distances support a phylogeny in which Ceratitis first branches off the common stem, then Chymomyza splits before the divergence of the two major Drosophila subgenera. The estimated divergence times are 58 million for Chymomyza-Drosophila; 48 million years for the Drosophila subgenera. During the intervening 10 million years, the Drosophila lineage lost the second intron and evolved distinct codon-preferences: the G + C use in the third coding positions is increased by 69% in Drosophila relative to Chymomyza or Ceratitis.
我们已经克隆并测序了嗜尸果蝇（Chymomyza amoena）的铜锌超氧化物歧化酶基因。其编码序列的长度与果蝇属物种以及地中海实蝇（Ceratitis capitata）中的相同。有两个内含子，其位置与地中海实蝇中的相同。果蝇属中不存在第二个内含子：这表明嗜尸果蝇处于果蝇谱系之外，这与基于解剖学和其他证据的推测相反。核苷酸或氨基酸距离支持这样一种系统发育关系，即地中海实蝇首先从共同主干分支出来，然后嗜尸果蝇在两个主要果蝇亚属分化之前分裂。估计嗜尸果蝇与果蝇的分化时间为5800万年；果蝇亚属的分化时间为4800万年。在这期间的1000万年里，果蝇谱系丢失了第二个内含子并进化出了不同的密码子偏好：相对于嗜尸果蝇或地中海实蝇，果蝇在第三个编码位置的G + C使用量增加了69%。
