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Valerie J. Paul - One of the best experts on this subject based on the ideXlab platform.
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differential gene expression during substrate probing in larvae of the caribbean coral Porites Astreoides
Molecular Ecology, 2019Co-Authors: Jennifer M Sneed, Valerie J. Paul, Nia S Walker, Rosa Fernandez, Gonzalo Giribet, David J ComboschAbstract:The transition from larva to adult is a critical step in the life history strategy of most marine animals. However, the genetic basis of this life history change remains poorly understood in many taxa, including most coral species. Recent evidence suggests that coral planula larvae undergo significant changes at the physiological and molecular levels throughout the development. To investigate this, we characterized differential gene expression (DGE) during the transition from planula to adult polyp in the abundant Caribbean reef-building coral Porites Astreoides, that is from nonprobing to actively substrate-probing larva, a stage required for colony initiation. This period is crucial for the coral, because it demonstrates preparedness to locate appropriate substrata for settlement based on vital environmental cues. Through RNA-Seq, we identified 860 differentially expressed holobiont genes between probing and nonprobing larvae (p ≤ .01), the majority of which were upregulated in probing larvae. Surprisingly, differentially expressed genes of endosymbiotic dinoflagellate origin greatly outnumbered coral genes, compared with a nearly 1:1 ratio of coral-to-dinoflagellate gene representation in the holobiont transcriptome. This unanticipated result suggests that dinoflagellate endosymbionts may play a significant role in the transition from nonprobing to probing behaviour in dinoflagellate-rich larvae. Putative holobiont genes were largely involved in protein and nucleotide binding, metabolism and transport. Genes were also linked to environmental sensing and response and integral signalling pathways. Our results thus provide detailed insight into molecular changes prior to larval settlement and highlight the complex physiological and biochemical changes that occur in early transition stages from pelagic to benthic stages in corals, and perhaps more importantly, in their endosymbionts.
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Macroalgal extracts induce bacterial assemblage shifts and sublethal tissue stress in Caribbean corals. PLoS One 2012
2016Co-Authors: Kathleen M. Morrow, Cliff Ross, Raphael Ritson-williams, Mark R. Liles, Valerie J. PaulAbstract:Benthic macroalgae can be abundant on present-day coral reefs, especially where rates of herbivory are low and/or dissolved nutrients are high. This study investigated the impact of macroalgal extracts on both coral-associated bacterial assemblages and sublethal stress response of corals. Crude extracts and live algal thalli from common Caribbean macroalgae were applied onto the surface of Montastraea faveolata and Porites Astreoides corals on reefs in both Florida and Belize. Denaturing gradient gel electrophoresis (DGGE) of 16S rRNA gene amplicons was used to examine changes in the surface mucus layer (SML) bacteria in both coral species. Some of the extracts and live algae induced detectable shifts in coral-associated bacterial assemblages. However, one aqueous extract caused the bacterial assemblages to shift to an entirely new state (Lobophora variegata), whereas other organic extracts had little to no impact (e.g. Dictyota sp.). Macroalgal extracts more frequently induced sublethal stress responses in M. faveolata than in P. Astreoides corals, suggesting that cellular integrity can be negatively impacted in selected corals when comparing co-occurring species. As modern reefs experience phase-shifts to a higher abundance of macroalgae with potent chemical defenses, these macroalgae are likely impacting the composition of microbial assemblages associated with corals and affecting overall ree
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differential larval settlement responses of Porites Astreoides and acropora palmata in the presence of the green alga halimeda opuntia
Coral Reefs, 2016Co-Authors: Jennifer M Sneed, Kevin Olsen, Valerie J. PaulAbstract:Settlement is critical to maintaining coral cover on reefs, yet interspecific responses of coral planulae to common benthic macroalgae are not well characterized. Larval survival and settlement of two Caribbean reef-building corals, the broadcast-spawner Acropora palmata and the planulae-brooder Porites Astreoides, were quantified following exposure to plastic algae controls and the green macroalga Halimeda opuntia. Survival and settlement rates were not significantly affected by the presence of H. opuntia in either species. However, ~10 % of P. Astreoides larvae settled on the surface of the macroalga, whereas larvae of A. palmata did not. It is unlikely that corals that settle on macroalgae will survive post-settlement; therefore, H. opuntia may reduce the number of P. Astreoides and other non-discriminatory larvae that survive to adulthood. Our results suggest that the presence of macroalgae on impacted reefs can have unexpected repercussions for coral recruitment and highlight discrepancies in settlement specificity between corals with distinct life history strategies.
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eggs and larvae of acropora palmata and larvae of Porites Astreoides contain high amounts of dimethylsulfoniopropionate
Journal of Experimental Marine Biology and Ecology, 2015Co-Authors: Jennifer L Debose, Ronald P Kiene, Valerie J. PaulAbstract:Abstract Coral holobionts, including their symbionts, are known to produce large amounts of dimethylsulfoniopropionate (DMSP), a compound which some corals use to mitigate oxidative stress; however, very little work has been done on the presence and use of DMSP in early life history stages of coral, such as in eggs and larvae. This study shows that eggs and larvae, from Acropora palmata, and brooded larvae, from Porites Astreoides, also contain high amounts of DMSP. Eggs and larvae of wild A. palmata were collected and contained extremely high levels of DMSP: 1.2 μmol per larva and 359 μmol per 100 μL eggs. Larvae of P. Astreoides were collected in flow-through laboratory tanks, from wild-collected parent colonies, over the course of the larval release cycle. In brooded larvae of P. Astreoides, the amount of DMSP in larvae ranged from 11.6 to 1510 nmol per larva; larval DMSP peaked by the second night of release and then decreased over the following release nights. These high levels in aposymbiotic eggs and larvae of A. palmata and the peaking trend in symbiotic larvae of P. Astreoides are suggestive of parental provisioning. Given the large amounts of DMSP found in eggs and larvae, this study provides further evidence that even early life stages of the coral holobiont may benefit from the presence of DMSP.
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direct effects of elevated temperature reduced ph and the presence of macroalgae dictyota spp on larvae of the caribbean coral Porites Astreoides
Bulletin of Marine Science, 2015Co-Authors: Kevin Olsen, Valerie J. Paul, Cliff RossAbstract:Through an aquarium-based study, we provide evidence that exposure to macroalgae (Dictyota spp.), seawater with reduced pH (7.6 vs 8.1), and elevated temperature (31.8 vs 28.8 °C) causes distinct and additive repercussions for larval settlement and condition (photochemical efficiency and oxidative stress). Larvae from the common Caribbean coral Porites Astreoides (Lamarck, 1816) were provided settlement substrate and exposed to each factor for 72 hrs in isolation and combination under an orthogonal design. Largely, biotic and abiotic factors did not interact in their impact on coral planulae; instead, stressors independently affected the survival, condition, and settlement of P. Astreoides. Dictyota spp. and low pH each individually reduced the survival of coral larvae. Furthermore, the presence of Dictyota spp. and elevated temperature distinctly inhibited larval settlement and photochemical efficiency, respectively. When combined, stressors additively increased cellular oxidative damage (lipid peroxidation) approximately four fold compared to larvae maintained under control conditions. The results indicate that each stressor independently impacts distinct and overlapping facets of coral settlement, and suggest that their combined effects could have severe collective consequences for coral demography.
Mikhail V Matz - One of the best experts on this subject based on the ideXlab platform.
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gene expression plasticity as a mechanism of coral adaptation to a variable environment
Nature Ecology and Evolution, 2017Co-Authors: Carly D Kenkel, Mikhail V MatzAbstract:Local adaptation is ubiquitous, but the molecular mechanisms that give rise to this ecological phenomenon remain largely unknown. A year-long reciprocal transplant of mustard hill coral (Porites Astreoides) between a highly environmentally variable inshore habitat and a more stable offshore habitat demonstrated that populations exhibit phenotypic signatures that are consistent with local adaptation. We characterized the genomic basis of this adaptation in both coral hosts and their intracellular symbionts (Symbiodinium sp.) using genome-wide gene expression profiling. Populations differed primarily in their capacity for plasticity: following transplantation to a novel environment, inshore-origin coral expression profiles became significantly more similar to the local population's profiles than those in offshore-origin corals. Furthermore, elevated plasticity of the environmental stress response expression was correlated with lower susceptibility to a natural summer bleaching event, suggesting that plasticity is adaptive in the inshore environment. Our results reveal a novel genomic mechanism of resilience to a variable environment, demonstrating that corals are capable of a more diverse molecular response to stress than previously thought. What are the molecular mechanisms underpinning local adaptation? Reciprocal transplant of mustard hill coral from a variable to a more stable habitat demonstrates that populations exhibit phenotypic signatures consistent with local adaptation.
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enhanced gene expression plasticity as a mechanism of adaptation to a variable environment in a reef building coral
bioRxiv, 2016Co-Authors: Carly D Kenkel, Mikhail V MatzAbstract:Local adaptation is ubiquitous, but the molecular mechanisms giving rise to this ecological phenomenon remain largely unknown. A year-long reciprocal transplant of mustard hill coral (Porites Astreoides) between a highly environmentally variable inshore habitat and more stable offshore habitat demonstrated that both inshore and offshore populations exhibit elevated growth, protein and lipid content in their home reef environment, indicative of local adaptation. Here, we characterized the genomic basis of this adaptation in both coral hosts and their intracellular algal symbionts (Symbiodinium sp.) using genome-wide gene expression profiling and gene coexpression network analysis. Inshore and offshore coral populations differ primarily in their capacity for gene expression plasticity: upon transplantation to a novel environment inshore corals were able to match expression profiles of the local population significantly better than offshore corals. Furthermore, elevated plasticity in expression of environmental stress response (ESR) genes was adaptive in the inshore environment: it correlated with the least susceptibility to a natural summer bleaching event, whereas higher constitutive ESR gene expression ("frontloading" sensu Barshis et al. 2013) did not. Our results reveal a novel genomic mechanism of resilience to a variable environment, demonstrating that corals are capable of a more diverse molecular response to environmental stress than previously thought.
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Pilot RNAseq Data
2016Co-Authors: Carly D Kenkel, Eli Meyer, Mikhail V MatzAbstract:This file contains cleaned SOLiD reads (in colorspace) and a table of read counts mapping to the Porites Astreoides transcriptome as described in the paper
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gene expression under chronic heat stress in populations of the mustard hill coral Porites Astreoides from different thermal environments
Molecular Ecology, 2013Co-Authors: Carly D Kenkel, Eli Meyer, Mikhail V MatzAbstract: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.
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evidence for a host role in thermotolerance divergence between populations of the mustard hill coral Porites Astreoides from different reef environments
Molecular Ecology, 2013Co-Authors: Carly D Kenkel, Gretchen Goodbodygringley, Damien Caillaud, Sarah W Davies, Erich Bartels, Mikhail V MatzAbstract:Studying the mechanisms that enable coral populations to inhabit spatially varying thermal environments can help evaluate how they will respond in time to the effects of global climate change and elucidate the evolutionary forces that enable or constrain adaptation. Inshore reefs in the Florida Keys experience higher temperatures than offshore reefs for prolonged periods during the summer. We conducted a common garden experiment with heat stress as our selective agent to test for local thermal adaptation in corals from inshore and offshore reefs. We show that inshore corals are more tolerant of a 6-week temperature stress than offshore corals. Compared with inshore corals, offshore corals in the 31 °C treatment showed significantly elevated bleaching levels concomitant with a tendency towards reduced growth. In addition, dinoflagellate symbionts (Symbiodinium sp.) of offshore corals exhibited reduced photosynthetic efficiency. We did not detect differences in the frequencies of major (>5%) haplotypes comprising Symbiodinium communities hosted by inshore and offshore corals, nor did we observe frequency shifts (‘shuffling’) in response to thermal stress. Instead, coral host populations showed significant genetic divergence between inshore and offshore reefs, suggesting that in Porites Astreoides, the coral host might play a prominent role in holobiont thermotolerance. Our results demonstrate that coral populations inhabiting reefs <10-km apart can exhibit substantial differences in their physiological response to thermal stress, which could impact their population dynamics under climate change.
Adina Paytan - One of the best experts on this subject based on the ideXlab platform.
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species specific calcification response of caribbean corals after 2 year transplantation to a low aragonite saturation submarine spring
Proceedings of The Royal Society B: Biological Sciences, 2019Co-Authors: Ana Martinez, Elizabeth D. Crook, Laura Hernandez, Daniel J Barshis, Donald C Potts, Mario Rebolledovieyra, Adina PaytanAbstract:Coral calcification is expected to decline as atmospheric carbon dioxide concentration increases. We assessed the potential of Porites Astreoides, Siderastrea siderea and Porites Porites to survive...
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Reduced calcification and lack of acclimatization by coral colonies growing in areas of persistent natural acidification
Proceedings of the National Academy of Sciences of the United States of America, 2013Co-Authors: Elizabeth D. Crook, Laura Hernandez, Anne L. Cohen, Mario Rebolledo-vieyra, Adina PaytanAbstract:As the surface ocean equilibrates with rising atmospheric CO2, the pH of surface seawater is decreasing with potentially negative impacts on coral calcification. A critical question is whether corals will be able to adapt or acclimate to these changes in seawater chemistry. We use high precision CT scanning of skeletal cores of Porites Astreoides, an important Caribbean reef-building coral, to show that calcification rates decrease significantly along a natural gradient in pH and aragonite saturation (Ωarag). This decrease is accompanied by an increase in skeletal erosion and predation by boring organisms. The degree of sensitivity to reduced Ωarag measured on our field corals is consistent with that exhibited by the same species in laboratory CO2 manipulation experiments. We conclude that the Porites corals at our field site were not able to acclimatize enough to prevent the impacts of local ocean acidification on their skeletal growth and development, despite spending their entire lifespan in low pH, low Ωarag seawater.
James M. Cervino - One of the best experts on this subject based on the ideXlab platform.
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Variation in Immune-Related Gene Expression Provides Evidence of Local Adaptation in Porites Astreoides (Lamarck, 1816) between Inshore and Offshore Meta-Populations Inhabiting the Lower Florida Reef Tract, USA
'MDPI AG', 2021Co-Authors: Joshua A. Haslun, Kevin B. Strychar, James M. Cervino, Briana Hauff-salas, Nathaniel E. OstromAbstract:Coral communities of the Florida Reef Tract (FRT) have changed dramatically over the past 30 years. Coral cover throughout the FRT is disproportionately distributed; >70% of total coral cover is found within the inshore patch reef zone (5 km from shore). Coral mortality from disease has been differentially observed between inshore and offshore reefs along the FRT. Therefore, differences between the response of inshore and offshore coral populations to bacterial challenge may contribute to differences in coral cover. We examined immune system activation in Porites Astreoides (Lamarck, 1816), a species common in both inshore and offshore reef environments in the FRT. Colonies from a representative inshore and offshore site were reciprocally transplanted and the expression of three genes monitored biannually for two years (two summer and two winter periods). Variation in the expression of eukaryotic translation initiation factor 3, subunit H (eIF3H), an indicator of cellular stress in Porites Astreoides, did not follow annual patterns of seawater temperatures (SWT) indicating the contribution of other stressors (e.g., irradiance). Greater expression of tumor necrosis factor (TNF) receptor associated factor 3 (TRAF3), a signaling protein of the inflammatory response, was observed among corals transplanted to, or located within the offshore environment indicating that an increased immune response is associated with offshore coral more so than the inshore coral (p < 0.001). Corals collected from the offshore site also upregulated the expression of adenylyl cyclase associated protein 2 (ACAP2), increases which are associated with decreasing innate immune system inflammatory responses, indicating a counteractive response to increased stimulation of the innate immune system. Activation of the innate immune system is a metabolically costly survival strategy. Among the two reefs studied, the offshore population had a smaller mean colony size and decreased colony abundance compared to the inshore site. This correlation suggests that tradeoffs may exist between the activation of the innate immune system and survival and growth. Consequently, immune system activation may contribute to coral community dynamics and declines along the FRT
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site specific variation in gene expression from symbiodinium spp associated with offshore and inshore Porites Astreoides in the lower florida keys is lost with bleaching and disease stress
PLOS ONE, 2017Co-Authors: Briana Hauff Salas, Joshua A. Haslun, Kevin B. Strychar, Peggy H. Ostrom, James M. CervinoAbstract:Scleractinian coral are experiencing unprecedented rates of mortality due to increases in sea surface temperatures in response to global climate change. Some coral species however, survive high temperature events due to a reduced susceptibility to bleaching. We investigated the relationship between bleaching susceptibility and expression of five metabolically related genes of Symbiodinium spp. from the coral Porites Astreoides originating from an inshore and offshore reef in the Florida Keys. The acclimatization potential of Symbiodinium spp. to changing temperature regimes was also measured via a two-year reciprocal transplant between the sites. Offshore coral fragments displayed significantly higher expression in Symbiodinium spp. genes PCNA, SCP2, G3PDH, PCP and psaE than their inshore counterparts (p<0.05), a pattern consistent with increased bleaching susceptibility in offshore corals. Additionally, gene expression patterns in Symbiodinium spp. from site of origin were conserved throughout the two-year reciprocal transplant, indicating acclimatization did not occur within this multi-season time frame. Further, laboratory experiments were used to investigate the influence of acute high temperature (32°C for eight hours) and disease (lipopolysaccharide of Serratia marcescens) on the five metabolically related symbiont genes from the same offshore and inshore P. Astreoides fragments. Gene expression did not differ between reef fragments, or as a consequence of acute exposure to heat or heat and disease, contrasting to results found in the field. Gene expression reported here indicates functional variation in populations of Symbiodinium spp. associated with P. Astreoides in the Florida Keys, and is likely a result of localized adaptation. However, gene expression patterns observed in the lab imply that functional variation in zooxanthellae observed under conditions of chronic moderate stress is lost under the acute extreme conditions studied here.
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Site-specific variation in gene expression from Symbiodinium spp. associated with offshore and inshore Porites Astreoides in the lower Florida Keys is lost with bleaching and disease stress
2017Co-Authors: Briana Hauff Salas, Joshua A. Haslun, Kevin B. Strychar, Peggy H. Ostrom, James M. CervinoAbstract:Scleractinian coral are experiencing unprecedented rates of mortality due to increases in sea surface temperatures in response to global climate change. Some coral species however, survive high temperature events due to a reduced susceptibility to bleaching. We investigated the relationship between bleaching susceptibility and expression of five metabolically related genes of Symbiodinium spp. from the coral Porites Astreoides originating from an inshore and offshore reef in the Florida Keys. The acclimatization potential of Symbiodinium spp. to changing temperature regimes was also measured via a two-year reciprocal transplant between the sites. Offshore coral fragments displayed significantly higher expression in Symbiodinium spp. genes PCNA, SCP2, G3PDH, PCP and psaE than their inshore counterparts (p
Carly D Kenkel - One of the best experts on this subject based on the ideXlab platform.
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gene expression plasticity as a mechanism of coral adaptation to a variable environment
Nature Ecology and Evolution, 2017Co-Authors: Carly D Kenkel, Mikhail V MatzAbstract:Local adaptation is ubiquitous, but the molecular mechanisms that give rise to this ecological phenomenon remain largely unknown. A year-long reciprocal transplant of mustard hill coral (Porites Astreoides) between a highly environmentally variable inshore habitat and a more stable offshore habitat demonstrated that populations exhibit phenotypic signatures that are consistent with local adaptation. We characterized the genomic basis of this adaptation in both coral hosts and their intracellular symbionts (Symbiodinium sp.) using genome-wide gene expression profiling. Populations differed primarily in their capacity for plasticity: following transplantation to a novel environment, inshore-origin coral expression profiles became significantly more similar to the local population's profiles than those in offshore-origin corals. Furthermore, elevated plasticity of the environmental stress response expression was correlated with lower susceptibility to a natural summer bleaching event, suggesting that plasticity is adaptive in the inshore environment. Our results reveal a novel genomic mechanism of resilience to a variable environment, demonstrating that corals are capable of a more diverse molecular response to stress than previously thought. What are the molecular mechanisms underpinning local adaptation? Reciprocal transplant of mustard hill coral from a variable to a more stable habitat demonstrates that populations exhibit phenotypic signatures consistent with local adaptation.
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enhanced gene expression plasticity as a mechanism of adaptation to a variable environment in a reef building coral
bioRxiv, 2016Co-Authors: Carly D Kenkel, Mikhail V MatzAbstract:Local adaptation is ubiquitous, but the molecular mechanisms giving rise to this ecological phenomenon remain largely unknown. A year-long reciprocal transplant of mustard hill coral (Porites Astreoides) between a highly environmentally variable inshore habitat and more stable offshore habitat demonstrated that both inshore and offshore populations exhibit elevated growth, protein and lipid content in their home reef environment, indicative of local adaptation. Here, we characterized the genomic basis of this adaptation in both coral hosts and their intracellular algal symbionts (Symbiodinium sp.) using genome-wide gene expression profiling and gene coexpression network analysis. Inshore and offshore coral populations differ primarily in their capacity for gene expression plasticity: upon transplantation to a novel environment inshore corals were able to match expression profiles of the local population significantly better than offshore corals. Furthermore, elevated plasticity in expression of environmental stress response (ESR) genes was adaptive in the inshore environment: it correlated with the least susceptibility to a natural summer bleaching event, whereas higher constitutive ESR gene expression ("frontloading" sensu Barshis et al. 2013) did not. Our results reveal a novel genomic mechanism of resilience to a variable environment, demonstrating that corals are capable of a more diverse molecular response to environmental stress than previously thought.
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Pilot RNAseq Data
2016Co-Authors: Carly D Kenkel, Eli Meyer, Mikhail V MatzAbstract:This file contains cleaned SOLiD reads (in colorspace) and a table of read counts mapping to the Porites Astreoides transcriptome as described in the paper
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gene expression under chronic heat stress in populations of the mustard hill coral Porites Astreoides from different thermal environments
Molecular Ecology, 2013Co-Authors: Carly D Kenkel, Eli Meyer, Mikhail V MatzAbstract: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.
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evidence for a host role in thermotolerance divergence between populations of the mustard hill coral Porites Astreoides from different reef environments
Molecular Ecology, 2013Co-Authors: Carly D Kenkel, Gretchen Goodbodygringley, Damien Caillaud, Sarah W Davies, Erich Bartels, Mikhail V MatzAbstract:Studying the mechanisms that enable coral populations to inhabit spatially varying thermal environments can help evaluate how they will respond in time to the effects of global climate change and elucidate the evolutionary forces that enable or constrain adaptation. Inshore reefs in the Florida Keys experience higher temperatures than offshore reefs for prolonged periods during the summer. We conducted a common garden experiment with heat stress as our selective agent to test for local thermal adaptation in corals from inshore and offshore reefs. We show that inshore corals are more tolerant of a 6-week temperature stress than offshore corals. Compared with inshore corals, offshore corals in the 31 °C treatment showed significantly elevated bleaching levels concomitant with a tendency towards reduced growth. In addition, dinoflagellate symbionts (Symbiodinium sp.) of offshore corals exhibited reduced photosynthetic efficiency. We did not detect differences in the frequencies of major (>5%) haplotypes comprising Symbiodinium communities hosted by inshore and offshore corals, nor did we observe frequency shifts (‘shuffling’) in response to thermal stress. Instead, coral host populations showed significant genetic divergence between inshore and offshore reefs, suggesting that in Porites Astreoides, the coral host might play a prominent role in holobiont thermotolerance. Our results demonstrate that coral populations inhabiting reefs <10-km apart can exhibit substantial differences in their physiological response to thermal stress, which could impact their population dynamics under climate change.