Gleason Lani U, Burton Ronald S
Marine Biology Research Division, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA, 92093-0202, USA.
Mol Ecol. 2015 Feb;24(3):610-27. doi: 10.1111/mec.13047.
To investigate the role of gene expression in adaptation of marine ectotherms to different temperatures, we examined the transcriptome-wide thermal stress response in geographically separated populations of the intertidal snail Chlorostoma funebralis. Snails from two southern (heat tolerant) and two northern (heat sensitive) populations were acclimated to a common thermal environment, exposed to an environmentally relevant thermal stress and analysed using RNA-seq. Pooling across all populations revealed 306 genes with differential expression between control and heat-stressed samples, including 163 significantly upregulated and 143 significantly downregulated genes. When considered separately, regional differences in response were widely apparent. Heat shock proteins (Hsps) were upregulated in both regions, but the magnitude of response was significantly greater in northern populations for most Hsp70s, while the southern populations showed greater upregulation for approximately half of the Hsp40s. Of 177 stress-responsive genes in northern populations, 55 responded to heat stress only in northern populations. Several molecular chaperones and antioxidant genes that were not differentially expressed in southern populations showed higher expression under control conditions compared with northern populations. This suggests that evolution of elevated expression of these genes under benign conditions preadapts the southern populations to frequent heat stress and contributes to their higher thermal tolerance. These results indicate that evolution has resulted in different transcriptome responses across populations, including upregulation of genes in response to stress and preadaptation of genes in anticipation of stress (based on evolutionary history of frequent heat exposure). The relative importance of the two mechanisms differs among gene families and among populations.
为了研究基因表达在海洋变温动物适应不同温度过程中的作用，我们检测了潮间带蜗牛加州笠螺地理隔离种群全转录组范围的热应激反应。来自两个南方（耐热）种群和两个北方（热敏感）种群的蜗牛被驯化到一个共同的热环境中，暴露于与环境相关的热应激下，并使用RNA测序进行分析。汇总所有种群的数据后发现，对照样本和热应激样本之间有306个基因存在差异表达，其中163个基因显著上调，143个基因显著下调。单独考虑时，反应的区域差异非常明显。热休克蛋白（Hsps）在两个区域均上调，但对于大多数Hsp70而言，北方种群的反应幅度显著更大，而南方种群中约一半的Hsp40上调幅度更大。在北方种群的177个应激反应基因中，有55个仅在北方种群中对热应激有反应。一些在南方种群中无差异表达的分子伴侣和抗氧化基因，与北方种群相比，在对照条件下表达更高。这表明这些基因在良性条件下表达升高的进化使南方种群预先适应频繁的热应激，并有助于它们具有更高的热耐受性。这些结果表明，进化导致了不同种群间转录组反应的差异，包括对应激的基因上调和对应激的预先适应（基于频繁热暴露的进化历史）。这两种机制的相对重要性在基因家族和种群之间有所不同。
