Understanding the genetic architecture of the stress response and its ability to evolve in response to different stressors requires an integrative approach. Here we quantify gene expression changes in response to two stressors associated with global climate change and habitat lossheat shock and mutation accumulation. We measure expression levels for two Heat Shock Proteins (HSP90 and HSP60)members of an important family of conserved molecular chaperones that have been shown to play numerous roles in the cell. While HSP90 assists with protein folding, stabilization, and degradation throughout the cell, HSP60 primarily localizes to the mitochondria and mediates de novo folding and stress-induced refolding of proteins. We perform these assays in Daphnia magna originally collected from multiple genotypes and populations along a latitudinal gradient, which differ in their annual mean, maximum, and range of temperatures. We find significant differences in overall expression between loci (10-fold), in response to thermal stress (typically, an order of magnitude) and with mutation accumulation (2-3x increase). Importantly, stressors interact synergistically to increase gene expression levels when more than one is applied. While there is no evidence for differences among the three populations assayed, individual genotypes vary considerably in HSP90 expression. Overall, our results support previous proposals that HSP90 may act as an important buffer against not only heat, but also mutation, and expands this hypothesis to include another member of the gene family.

中文翻译：

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水蚤中热休克蛋白基因的表达随着热应激和突变积累的增加而变化更大

要了解压力反应的遗传结构及其对不同压力源的反应能力，需要采取综合方法。在这里，我们量化了与全球气候变化和栖息地流失，热休克和突变积累相关的两个应激源的基因表达变化。我们测量两个重要分子保守分子伴侣的热休克蛋白（HSP90和HSP60）成员的表达水平，这些分子已显示在细胞中起着许多作用。虽然HSP90有助于整个细胞内的蛋白质折叠，稳定和降解，但HSP60主要定位于线粒体并介导从头折叠和应力诱导的蛋白质重新折叠。我们在大型蚤中进行这些测定最初是从多个基因型和种群沿纬度梯度收集的，它们的年均值，最高值和温度范围不同。我们发现基因座之间的整体表达（10倍），响应热应激（通常为一个数量级）和突变积累（2-3倍增加）之间存在显着差异。重要的是，当施加多个时，应激源协同相互作用以增加基因表达水平。尽管没有证据表明所分析的三个人群之间存在差异，但各个基因型在HSP90表达中差异很大。总的来说，我们的研究结果支持了以前的提议，即HSP90不仅可以抵抗热量，而且可以抵抗突变，并扩大了这一假设，使其包括基因家族的另一个成员。