Publication Date:
2012-09-06
Description:
Background: Geographic variation in the thermal environment impacts a broad range of biochemical andphysiological processes and can be a major selective force leading to local populationadaptation. In the intertidal copepod Tigriopus californicus, populations along the coast ofCalifornia show differences in thermal tolerance that are consistent with adaptation, i.e.,southern populations withstand thermal stresses that are lethal to northern populations. Tounderstand the genetic basis of these physiological differences, we use an RNA-seq approachto compare genome-wide patterns of gene expression in two populations known to differ inthermal tolerance. Results: Observed differences in gene expression between the southern (San Diego) and the northern(Santa Cruz) populations included both the number of affected loci as well as the identity ofthese loci. However, the most pronounced differences concerned the amplitude of upregulationof genes producing heat shock proteins (Hsps) and genes involved inubiquitination and proteolysis. Among the hsp genes, orthologous pairs show markedlydifferent thermal responses as the amplitude of hsp response was greatly elevated in the SanDiego population, most notably in members of the hsp70 gene family. There was no evidenceof accelerated evolution at the sequence level for hsp genes. Among other sets of genes,cuticle genes were up-regulated in SD but down-regulated in SC, and mitochondrial geneswere down-regulated in both populations. Conclusions: Marked changes in gene expression were observed in response to acute sub-lethal thermalstress in the copepod T. californicus. Although some qualitative differences were observedbetween populations, the most pronounced differences involved the magnitude of inductionof numerous hsp and ubiquitin genes. These differences in gene expression suggest thatevolutionary divergence in the regulatory pathway(s) involved in acute temperature stressmay offer at least a partial explanation of population differences in thermal toleranceobserved in Tigriopus.
Electronic ISSN:
1471-2148
Topics:
Biology
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