Gene expression under chronic heat stress in populations of the mustard hill coral (Porites astreoides) from different thermal environments

Abstract

Recent evidence suggests that corals can acclimatize or adapt to local stress factors through differential regulation of their gene expression. Profiling gene expression in corals from diverse environments can elucidate the physiological processes that may be responsible for maximizing coral fitness in their natural habitat and lead to a better understanding of the coral's capacity to survive the effects of global climate change. In an accompanying paper, we show that Porites astreoides from thermally different reef habitats exhibit distinct physiological responses when exposed to 6 weeks of chronic temperature stress in a common garden experiment. Here, we describe expression profiles obtained from the same corals for a panel of 9 previously reported and 10 novel candidate stress response genes identified in a pilot RNA-Seq experiment. The strongest expression change was observed in a novel candidate gene potentially involved in calcification, SLC26, a member of the solute carrier family 26 anion exchangers, which was down-regulated by 92-fold in bleached corals relative to controls. The most notable signature of divergence between coral populations was constitutive up-regulation of metabolic genes in corals from the warmer inshore location, including the gluconeogenesis enzymes pyruvate carboxylase and phosphoenolpyruvate carboxykinase and the lipid beta-oxidation enzyme acyl-CoA dehydrogenase. Our observations highlight several molecular pathways that were not previously implicated in the coral stress response and suggest that host management of energy budgets might play an adaptive role in holobiont thermotolerance.

Heritable differences in fitness-related traits among populations of the mustard hill coral, Porites astreoides

“…Inshore and offshore adult P. astreoides display gene expression patterns that may reflect alternative energy allocation strategies (Kenkel et al, 2013b). Similar variation in recruit populations could underpin the differences in growth rates through time and in response to temperature stress, but additional transcriptomic studies are needed to validate this hypothesis.…”

“…These populations harbor indistinguishable Symbiodinium phylotypes but hosts are significantly genetically differentiated (Kenkel et al, 2013a) and exhibit divergent gene expression patterns (Kenkel et al, 2013b) suggesting that the coral host has a more prominent role in thermal adaptation in this species. However, it is not clear if observed thermotolerance differences in these populations are the result of heritable genetic variation or long-term acclimatization to their native habitat.…”

Investigating the Driving Mechanisms Behind Differences in Bleaching and Disease Susceptibility Between Two Scleractinian Corals, Pseudodiploria Strigosa and Diploria Labyrinthiformis

“…For example, the upregulation of collagen-associated proteins has been found in more thermally-tolerant individuals , Kenkel et al 2013. However, in the present study collagen was upregulated for both species in Summer 2013, suggesting that collagen does not play a role in the different susceptibilities of D. labyrinthiformis and P. strigosa.…”

“…Heat shock proteins (HSPs) are commonly the focus of cnidarian thermal stress studies (Leggat et al 2011), however they may not tell the entire story, as they are absent in several studies of coral heat stress (the present study and , and have been shown to decrease in expression levels a mere 10 hours after the initial temperature change (Rodriguez-Lanetty et al 2009). Heat shock proteins can also be unexpectedly downregulated, for example HSP90 was downregulated in Porites astreoides (Kenkel et al 2013). Sharp et al (1997) reported a downregulated in HSP70 in Goniopora dljiboutiensis.…”

“…astreoides (Kenkel et al 2013), and the ubiquitin conjugating enzyme E2 was downregulated in larval A. millepora subject to thermal stress (Meyer et al 2011). …”