Transcriptomic responses to heat stress in invasive and native blue mussels (genus Mytilus): molecular correlates of invasive success

Abstract

SUMMARYInvasive species are increasingly prevalent in marine ecosystems worldwide. Although many studies have examined the ecological effects of invasives, little is known about the physiological mechanisms that might contribute to invasive success. The mussel Mytilus galloprovincialis, a native of the Mediterranean Sea, is a successful invader on the central and southern coasts of California, where it has largely displaced the native congener, Mytilus trossulus. It has been previously shown that thermal responses of several physiological traits may underlie the capacity of M. galloprovincialis to out-compete M. trossulus in warm habitats. To elucidate possible differences in stress-induced gene expression between these congeners, we developed an oligonucleotide microarray with 8874 probes representing 4488 different genes that recognized mRNAs of both species. In acute heat-stress experiments, 1531 of these genes showed temperature-dependent changes in expression that were highly similar in the two congeners. By contrast, 96 genes showed species-specific responses to heat stress, functionally characterized by their involvement in oxidative stress, proteolysis, energy metabolism, ion transport, cell signaling and cytoskeletal reorganization. The gene that showed the biggest difference between the species was the gene for the molecular chaperone small heat shock protein 24, which was highly induced in M. galloprovincialis and showed only a small change in M. trossulus. These different responses to acute heat stress may help to explain -and predict -the invasive success of M. galloprovincialis in a warming world. Supplementary material available online at

Temperature and CO2additively regulate physiology, morphology and genomic responses of larval sea urchins,Strongylocentrotus purpuratus

“…Transcriptomic and proteomic analysis of mussels (Mytilus spp.) from the California Current supports this hypothesis and indicates that the protection of the cytoskeleton is not only a key response to acute heat stress but may also underlie the evolution of increased thermotolerance [71,72]. Nonetheless, the induction of cytoskeletal proteins was lower when both temperature and pCO 2 were increased, implying that simultaneous exposure to high temperature and pCO 2 can affect the cytoskeleton differently than when either stressor is applied independently, and given the role played by the cytoskeleton in basic cellular processes, this may have unresolved consequences for cell function in future oceans.…”

Genomic mechanisms of evolved physiological plasticity in killifish distributed along an environmental salinity gradient

“…However, these studies have tended to compare gene expression across taxa in static common-garden environments. In contrast, much functionally relevant variation is likely to be revealed within experimental designs that manipulate environmental conditions such that transcriptomewide norms of reaction can be compared across taxa (49)(50)(51). These designs, including the experiments presented here, promise to offer more nuanced insight into the functional relevance of genes with expression patterns that vary in response to the environment and vary across taxa from different native environments.…”

Micro-scale environmental variation amplifies physiological variation among individual mussels

“…The rate of production of ROS is inherently linked to metabolism [32,33], and it tends to increase when organisms are pushed towards their thermal limits and/or when they are exposed to cycles of hypoxia and reoxygenation [32][33][34][35]. Although mussels' physiologies appear well suited to the oxidative stress potentially engendered by their intermittently warm and hypoxic lifestyle (coinciding when the shell valves are closed at low tide; [36,37]), available data support a role for variation in susceptibility to oxidative stress in setting different thermal tolerance limits among Mytilus congeners [38,39]. We quantify biochemical indices of variation among individuals in the antioxidant capacity to cope with sublethal thermal stress.…”