Laurie C C, Heath E M, Jacobson J W, Thomson M S
Department of Zoology, Duke University, Durham, NC 27706.
Proc Natl Acad Sci U S A. 1990 Dec;87(24):9674-8. doi: 10.1073/pnas.87.24.9674.
Drosophila melanogaster and its sibling species, Drosophila simulans, differ in expression of the enzyme alcohol dehydrogenase (ADH). Adult melanogaster flies that are homozygous for the Slow allozyme have approximately twice the level of ADH activity and crossreacting material as simulans adults. There is no corresponding difference in ADH mRNA, however, so this difference in ADH protein level is evidently due to a difference in the rate of translation of the two RNAs and/or to a difference in protein stability. Here we report an interspecific gene-transfer experiment, using P-element transformation, to determine whether this expression difference is due to genetic background differences between the species (trans-acting modifiers) or to cis-acting factors within the Adh gene. When the Adh genes from D. melanogaster and D. simulans are put into the same genetic background, there is no detectable difference in their level of expression. The level is relatively high in the melanogaster background and relatively low in the simulans background. Therefore, the interspecific difference in Adh expression is due entirely to trans-acting modifiers, in spite of the many sequence differences between the Adh genes of the two species, which include two amino acid substitutions.
黑腹果蝇及其近缘种拟果蝇在乙醇脱氢酶（ADH）的表达上存在差异。纯合慢等位基因的成年黑腹果蝇的ADH活性水平和交叉反应物质大约是拟果蝇成虫的两倍。然而，ADH mRNA没有相应的差异，所以ADH蛋白水平的这种差异显然是由于两种RNA翻译速率的差异和/或蛋白质稳定性的差异。在此，我们报告一项种间基因转移实验，利用P因子转化来确定这种表达差异是由于物种间的遗传背景差异（反式作用修饰因子）还是由于Adh基因内的顺式作用因子。当将黑腹果蝇和拟果蝇的Adh基因置于相同的遗传背景中时，它们的表达水平没有可检测到的差异。在黑腹果蝇背景中水平相对较高，在拟果蝇背景中相对较低。因此，尽管两个物种的Adh基因之间存在许多序列差异，包括两个氨基酸替换，但Adh表达的种间差异完全是由于反式作用修饰因子。
