Genetic coadaptation of the amylase gene system in Drosophila melanogaster:: Evidence for the selective advantage of the lowest AMY activity and of its epistatic genetic background
Genetic coadaptation of the amylase gene system in Drosophila melanogaster:: Evidence for the selective advantage of the lowest AMY activity and of its epistatic genetic background
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DOI：
10.1093/jhered/esi051
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发表时间：
2005-07-01
影响因子：
3.1
通讯作者：
Yamazaki, T
中科院分区：
文献类型：
--
作者：
Araki, H;Yoshizumi, S;Yamazaki, T
在黑腹果蝇的自然种群中，具有最低α-淀粉酶活性的淀粉酶同工酶（AMY（1，1））占优势。为了评估AMY（1，1）及其调节因子的选择意义，我们在两种不同的食物环境中对实验室种群进行了选择实验。300代后，AMY（1，1）在富含葡萄糖（AMY的产物）的环境中成为优势（89%），而具有较高α-淀粉酶活性的同工酶AMY（1，6）在富含淀粉（底物）的环境中成为优势（83%）。我们发现，相同的等位基因的淀粉酶（艾米）基因，编码AMY（1，1）和AMY（1，6），共享两个群体之间在不同的食物环境，采用重复的艾米基因的核苷酸测序。然而，在富含淀粉的环境中选择的AMY（1，6）纯合子的AMY酶活性比在富含葡萄糖的环境中选择的高两倍，这表明编码区及其调控因子在遗传背景上的共适应。在AMY（1，1）纯合子之间没有检测到AMY酶活性的这种差异，这表明遗传背景的影响是上位性的。我们的研究结果表明，自然选择是对艾米基因系统作为一个整体的苍蝇，以适应当地人口的各种食物环境。
In natural populations of Drosophila melanogaster, an amylase isozyme with the lowest alpha-amylase activity (AMY(1,1)) is predominant. To evaluate the selective significance of AMY(1,1) and its regulatory factor(s), we examined selection experiments in laboratory populations on two distinct food environments. After 300 generations, AMY(1,1) became predominant (89%) in a glucose (a product of AMY)-rich environment, while an isozyme with higher alpha-amylase activity, AMY(1,6), became predominant (83%) in a starch (substrate)-rich environment. We found that the identical alleles of the amylase (Amy) gene, which encodes each of AMY(1,1) and AMY(1,6), were shared between the two populations in the different food environments, employing the nucleotide sequencing of the duplicated Amy genes. Nevertheless, AMY(1,6) homozygotes selected in the starch-rich environment had a twofold higher AMY enzyme activity than those selected in the glucose-rich environment, suggesting a coadaptation of the coding region and its regulatory factor(s) on the genetic background. Such a difference in AMY enzyme activity was not detected between AMY(1,1) homozygotes, suggesting that the effect of the genetic background is epistatic. Our results indicate that natural selection is working on the Amy gene system as a whole for flies to adapt to the various food environments of local populations.