Department of Biology, University of Rochester, Rochester, NY 14627, USA.
Mol Ecol. 2012 Sep;21(17):4287-99. doi: 10.1111/j.1365-294X.2012.05697.x. Epub 2012 Jul 9.
Gene expression responds to the environment and can also evolve rapidly in response to altered selection regimes. Little is known, however, about the extent to which evolutionary adaptation to a particular type of stress involves changes in the within-generation ('plastic') responses of gene expression to the stress. We used microarrays to quantify gene expression plasticity in response to ethanol in laboratory populations of Drosophila melanogaster differing in their history of ethanol exposure. Two populations ('R' populations) were maintained on regular medium, two ('E') were maintained on medium supplemented with ethanol, and two ('M') were maintained in a mixed regime in which half of the population was reared on one medium type, and half on the other, each generation. After more than 300 generations, embryos from each population were collected and exposed to either ethanol or water as a control, and RNA was extracted from the larvae shortly after hatching. Nearly 2000 transcripts showed significant within-generation responses to ethanol exposure. Evolutionary history also affected gene expression: the E and M populations were largely indistinguishable in expression, but differed significantly in expression from the R populations for over 100 transcripts, the majority of which did not show plastic responses. Notably, in no case was the interaction between selection regime and ethanol exposure significant after controlling for multiple comparisons, indicating that adaptation to ethanol in the E and M populations did not involve substantial changes in gene expression plasticity. The results give evidence that expression plasticity evolves considerably more slowly than mean expression.
基因表达会对环境做出响应，而且在应对改变的选择压力时也能迅速进化。然而，人们对于特定类型的压力下，基因表达在代内（“可塑性”）对压力的响应发生变化的程度，以及这种变化在多大程度上涉及进化适应，知之甚少。我们使用微阵列来量化实验室中不同乙醇暴露史的黑腹果蝇（Drosophila melanogaster）种群对乙醇的基因表达可塑性。两个种群（“R 种群”）在常规培养基上培养，两个种群（“E 种群”）在添加乙醇的培养基上培养，两个种群（“M 种群”）在混合培养条件下培养，其中一半的种群在一种培养基中饲养，另一半在另一种培养基中饲养，每一代都是如此。经过 300 多代后，从每个种群收集胚胎并暴露于乙醇或水（对照）中，然后在孵化后不久从幼虫中提取 RNA。近 2000 个转录本显示出对乙醇暴露的显著代内响应。进化历史也影响了基因表达：E 种群和 M 种群在表达上基本没有区别，但与 R 种群在超过 100 个转录本上的表达存在显著差异，其中大多数转录本没有表现出可塑性响应。值得注意的是，在控制多重比较后，选择压力和乙醇暴露之间的相互作用在任何情况下都不显著，这表明 E 种群和 M 种群对乙醇的适应并没有涉及基因表达可塑性的实质性变化。研究结果表明，与平均表达相比，表达可塑性的进化速度要慢得多。
