Project description:Southern California (USA) populations of the intertidal marine snail Chlorostoma (formerly Tegula) funebralis are generally exposed to higher air and water temperatures than northern California populations. Previous studies have shown that southern populations are more tolerant of heat stress than northern populations. To assess the potential role of gene regulation in these regional differences, we examined transcriptome responses to thermal stress in two southern and two northern populations of C. funebralis. Snails from the four populations were acclimated to a common lab environment, exposed to a heat stress representative of natural low tide conditions, and then analyzed using RNA-Seq to characterize changes in gene expression associated with stress and differences in expression across geographic regions. Changes in expression following stress were dominated by genes involved in apoptosis, the inflammatory response, response to mis and unfolded proteins, and ubiquitination of proteins. Heat shock proteins (Hsps) were up-regulated in both northern and southern populations. However, while the magnitude of the response was significantly greater in northern populations for the majority of Hsp70s, the southern populations showed a greater up-regulation for roughly half of the Hsp40s, which are co-chaperones for Hsp70s. Differential expression analysis of the control versus treatment genes in the northern and southern populations respectively revealed that 56 genes, many involved in the inflammation and immune response, responded to heat stress only in the northern populations. Moreover, several of the molecular chaperones and antioxidant genes that were not differentially expressed in the southern populations instead showed higher constitutive expression under control conditions compared to the northern populations. The expression levels of some of these constitutive genes such as superoxide dismutase were also found to positively correlate with survival following heat stress. This suggests that expression of these genes has evolved a degree of M-bM-^@M-^\frontloadingM-bM-^@M-^] that may contribute to the higher thermal tolerance of southern populations. mRNA profiles of northern and southern California heat-stressed and control C. funebralis were generated by 100bp paired end sequencing, in duplicate, using Illumina HiSeq2000.

Project description:Southern California (USA) populations of the intertidal marine snail Chlorostoma (formerly Tegula) funebralis are generally exposed to higher air and water temperatures than northern California populations. Previous studies have shown that southern populations are more tolerant of heat stress than northern populations. To assess the potential role of gene regulation in these regional differences, we examined transcriptome responses to thermal stress in two southern and two northern populations of C. funebralis. Snails from the four populations were acclimated to a common lab environment, exposed to a heat stress representative of natural low tide conditions, and then analyzed using RNA-Seq to characterize changes in gene expression associated with stress and differences in expression across geographic regions. Changes in expression following stress were dominated by genes involved in apoptosis, the inflammatory response, response to mis and unfolded proteins, and ubiquitination of proteins. Heat shock proteins (Hsps) were up-regulated in both northern and southern populations. However, while the magnitude of the response was significantly greater in northern populations for the majority of Hsp70s, the southern populations showed a greater up-regulation for roughly half of the Hsp40s, which are co-chaperones for Hsp70s. Differential expression analysis of the control versus treatment genes in the northern and southern populations respectively revealed that 56 genes, many involved in the inflammation and immune response, responded to heat stress only in the northern populations. Moreover, several of the molecular chaperones and antioxidant genes that were not differentially expressed in the southern populations instead showed higher constitutive expression under control conditions compared to the northern populations. The expression levels of some of these constitutive genes such as superoxide dismutase were also found to positively correlate with survival following heat stress. This suggests that expression of these genes has evolved a degree of “frontloading” that may contribute to the higher thermal tolerance of southern populations.

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