Loggerhead sea turtle embryos (Caretta caretta) regulate expression of stress response and developmental genes when exposed to a biologically realistic heat stress

Abstract

Oviparous reptile embryos are expected to breach their critical thermal maxima if temperatures reach those predicted under current climate change models due to the lack of the maternal buffering processes and parental care. Heat-shock proteins (HSPs) are integral in the molecular response to thermal stress, and their expression is heritable, but the roles of other candidate families such as the heat-shock factors (HSFs) have not been determined in reptiles. Here, we subject embryonic sea turtles (Caretta caretta) to a biologically realistic thermal stress and employ de novo transcriptomic profiling of brain tissue to investigate the underlying molecular response. From a reference transcriptome of 302 293 transcripts, 179 were identified as differentially expressed between treatments. As anticipated, genes enriched in the heat-shock treatment were primarily associated with the Hsp families, or were genes whose products play similar protein editing and chaperone functions (e.g. bag3, MYOC and serpinh1). Unexpectedly, genes encoding the HSFs were not significantly upregulated under thermal stress, indicating their presence in unstressed cells in an inactive state. Genes that were downregulated under thermal stress were less well functionally defined but were associated with stress response, development and cellular organization, suggesting that developmental processes may be compromised at realistically high temperatures. These results confirm that genes from the Hsp families play vital roles in the thermal tolerance of developing reptile embryos and, in addition with a number of other genes, should be targets for evaluating the capacity of oviparous reptiles to respond adaptively to the effects of climate change.

Managing consequences of climate‐driven species redistribution requires integration of ecology, conservation and social science

“…The mechanistic basis behind variability in thermal tolerance remains poorly understood (Clark, Sandblom & Jutfelt, ) but may be revealed through new genetic tools (Bentley et al, ). Measuring genetic diversity as organisms expand their range and documenting genetic structure during and after colonisation can provide a wealth of information on evolutionary dynamics of range shifts (McInerny et al, ; Sexton, Strauss & Rice, ; Duputié et al, ), but requires new, dedicated research programs and/or careful analysis of historical museum collections.…”

Comparative transcriptional profiling analysis of the effect of heat waves during embryo incubation on the hatchlings of the Chinese soft‐shelled turtle (Pelodiscus sinensis)

“…Heat‐shock proteins are also associated with changes in temperature. In loggerhead sea turtle, the expression of genes in the heat‐shock protein family was upregulated after heat‐shock treatment (Bentley, Haas, Tedeschi, & Berry, ), and in invertebrates, heat‐shock proteins were found to be differentially expressed after heat treatment (DeSalvo et al., ; Gleason & Burton, ; Huang et al., ). However, we did not observe differential expression of heat‐shock proteins in Chinese soft‐shelled turtles.…”

Genetic adaptation as a biological buffer against climate change: Potential and limitations

“…Mechanisms that may lead to higher heat tolerance involve biochemical adaptation (e.g. heat shock proteins; Tomanek 2010; Bentley et al 2017) and a smaller body size (Daufresne et al 2009;Brans et al 2017a). Evolution of heat tolerance is especially important for species already close to their upper thermal boundaries where plasticity in upper thermal limits is unlikely to effectively buffer effects of global warming (Tewksbury et al 2008;Araújo et al 2013;Sørensen et al 2015;van Heerwaarden et al 2016) and may be enhanced by exposure of hidden genetic variation ).…”