Project description:The declining health of coral reefs worldwide is likely to intensify in response to continued anthropogenic disturbance from coastal development, pollution, and climate change. In response to these stresses, reef-building corals may exhibit bleaching, which marks the breakdown in symbiosis between coral and zooxanthellae. Mass coral bleaching due to elevated water temperature can devastate coral reefs on a large geographic scale. In order to understand the molecular and cellular basis of bleaching in corals, we have measured gene expression changes associated with thermal stress and bleaching using a cDNA microarray containing 1,310 genes of the Caribbean coral Montastraea faveolata. In a first experiment, we identified differentially expressed genes by comparing experimentally bleached M. faveolata fragments to control non-heat-stressed fragments. We also identified differentially expressed genes during a time course experiment with four time points across nine days. Results suggest that thermal stress and bleaching in M. faveolata affect the following processes: oxidative stress, Ca2+ homeostasis, cytoskeletal organization, cell death, calcification, metabolism, protein synthesis, heat shock protein activity, and transposon activity. These results represent the first large-scale transcriptomic study focused on revealing the cellular foundation of thermal stress-induced coral bleaching. We postulate that oxidative stress in thermal-stressed corals causes a disruption of Ca2+ homeostasis, which in turn leads to cytoskeletal and cell adhesion changes, decreased calcification, and the initiation of cell death via apoptosis and necrosis. Keywords: thermal stress response, time course, coral bleaching
Project description:The declining health of coral reefs worldwide is likely to intensify in response to continued anthropogenic disturbance from coastal development, pollution, and climate change. In response to these stresses, reef-building corals may exhibit bleaching, which marks the breakdown in symbiosis between coral and zooxanthellae. Mass coral bleaching due to elevated water temperature can devastate coral reefs on a large geographic scale. In order to understand the molecular and cellular basis of bleaching in corals, we have measured gene expression changes associated with thermal stress and bleaching using a cDNA microarray containing 1,310 genes of the Caribbean coral Montastraea faveolata. In a first experiment, we identified differentially expressed genes by comparing experimentally bleached M. faveolata fragments to control non-heat-stressed fragments. We also identified differentially expressed genes during a time course experiment with four time points across nine days. Results suggest that thermal stress and bleaching in M. faveolata affect the following processes: oxidative stress, Ca2+ homeostasis, cytoskeletal organization, cell death, calcification, metabolism, protein synthesis, heat shock protein activity, and transposon activity. These results represent the first large-scale transcriptomic study focused on revealing the cellular foundation of thermal stress-induced coral bleaching. We postulate that oxidative stress in thermal-stressed corals causes a disruption of Ca2+ homeostasis, which in turn leads to cytoskeletal and cell adhesion changes, decreased calcification, and the initiation of cell death via apoptosis and necrosis. Keywords: thermal stress response; coral bleaching
Project description:The declining health of coral reefs worldwide is likely to intensify in response to continued anthropogenic disturbance from coastal development, pollution, and climate change. In response to these stresses, reef-building corals may exhibit bleaching, which marks the breakdown in symbiosis between coral and zooxanthellae. Mass coral bleaching due to elevated water temperature can devastate coral reefs on a large geographic scale. In order to understand the molecular and cellular basis of bleaching in corals, we have measured gene expression changes associated with thermal stress and bleaching using a cDNA microarray containing 1,310 genes of the Caribbean coral Montastraea faveolata. In a first experiment, we identified differentially expressed genes by comparing experimentally bleached M. faveolata fragments to control non-heat-stressed fragments. We also identified differentially expressed genes during a time course experiment with four time points across nine days. Results suggest that thermal stress and bleaching in M. faveolata affect the following processes: oxidative stress, Ca2+ homeostasis, cytoskeletal organization, cell death, calcification, metabolism, protein synthesis, heat shock protein activity, and transposon activity. These results represent the first large-scale transcriptomic study focused on revealing the cellular foundation of thermal stress-induced coral bleaching. We postulate that oxidative stress in thermal-stressed corals causes a disruption of Ca2+ homeostasis, which in turn leads to cytoskeletal and cell adhesion changes, decreased calcification, and the initiation of cell death via apoptosis and necrosis. Keywords: thermal stress response; coral bleaching 5 control and 5 heat-stressed RNA samples were hybridized in a 5-replicate dye-swap design (10 total hyb's).
Project description:The declining health of coral reefs worldwide is likely to intensify in response to continued anthropogenic disturbance from coastal development, pollution, and climate change. In response to these stresses, reef-building corals may exhibit bleaching, which marks the breakdown in symbiosis between coral and zooxanthellae. Mass coral bleaching due to elevated water temperature can devastate coral reefs on a large geographic scale. In order to understand the molecular and cellular basis of bleaching in corals, we have measured gene expression changes associated with thermal stress and bleaching using a cDNA microarray containing 1,310 genes of the Caribbean coral Montastraea faveolata. In a first experiment, we identified differentially expressed genes by comparing experimentally bleached M. faveolata fragments to control non-heat-stressed fragments. We also identified differentially expressed genes during a time course experiment with four time points across nine days. Results suggest that thermal stress and bleaching in M. faveolata affect the following processes: oxidative stress, Ca2+ homeostasis, cytoskeletal organization, cell death, calcification, metabolism, protein synthesis, heat shock protein activity, and transposon activity. These results represent the first large-scale transcriptomic study focused on revealing the cellular foundation of thermal stress-induced coral bleaching. We postulate that oxidative stress in thermal-stressed corals causes a disruption of Ca2+ homeostasis, which in turn leads to cytoskeletal and cell adhesion changes, decreased calcification, and the initiation of cell death via apoptosis and necrosis. Keywords: thermal stress response, time course, coral bleaching Time course with 4 time points and 4 biological replicates per time point. Each biological replicate at each time point was hybridized to a pooled reference control sample containing RNA from all control non-heat-stressed coral fragments.
Project description:Coral reefs worldwide are facing rapid decline due to coral bleaching. However, knowledge of the physiological characteristics and molecular mechanisms of coral symbionts respond to stress is scarce. Here, metagenomic and metaproteomic approach were utilized to shed light on the changes in the composition and functions of coral symbionts during coral bleaching. The results demonstrated that coral bleaching significantly affected the composition of symbionts, with bacterial communities dominating in bleached corals. Difference analysis of gene and protein indicated that symbiont functional disturbances in response to heat stress, resulting in abnormal energy metabolism that could potentially compromise symbiont health and resilience. Furthermore, our findings highlighted the highly diverse microbial communities of coral symbionts, with beneficial bacteria provide critical services to corals in stress responses, while pathogenic bacteria drive coral bleaching. This study provides comprehensive insights into the complex response mechanisms of coral symbionts under thermal stress and offers fundamental data for future monitoring of coral health.
Project description:Coral bleaching occurs in response to numerous abiotic stressors, the ecologically most relevant of which is hyperthermic stress due to increasing seawater temperatures. Bleaching events can span large geographic areas and are currently a potent threat to coral reefs worldwide. Much effort has been focused on understanding the molecular and cellular events underlying bleaching, and these studies have mainly utilized heat and light stress regimes. In an effort to determine whether different stressors share common bleaching mechanisms, we used cDNA microarrays for the corals Acropora palmata and Montastraea faveolata (containing > 10,000 features) to measure differential gene expression during darkness stress. This is the first coral microarray experiment aimed at darkness stress, and the first for these species to interrogate gene expression at such a large scale. Our results reveal a striking transcriptomic response to darkness in A. palmata involving chaperone and antioxidant up-regulation, growth arrest, and metabolic modifications. As these responses were also measured during thermal stress, our results suggest that different stressors may share common bleaching mechanisms. Furthermore, our results point to ER stress as a critical cellular event involved in darkness-specific (and possibly more general) molecular bleaching mechanisms. On the other hand, we identified a meager transcriptomic response to darkness in M. faveolata where gene expression differences between host colonies and/or sampling locations were greater than differences between control and stressed fragments. To this end, we discuss the importance of factors related to host genotype, Symbiodinium genotype, and the abiotic environment that influence host gene expression and thereby can hinder an investigator’s ability to measure gene expression during a condition of interest.
Project description:Coral bleaching occurs in response to numerous abiotic stressors, the ecologically most relevant of which is hyperthermic stress due to increasing seawater temperatures. Bleaching events can span large geographic areas and are currently a potent threat to coral reefs worldwide. Much effort has been focused on understanding the molecular and cellular events underlying bleaching, and these studies have mainly utilized heat and light stress regimes. In an effort to determine whether different stressors share common bleaching mechanisms, we used cDNA microarrays for the corals Acropora palmata and Montastraea faveolata (containing > 10,000 features) to measure differential gene expression during darkness stress. This is the first coral microarray experiment aimed at darkness stress, and the first for these species to interrogate gene expression at such a large scale. Our results reveal a striking transcriptomic response to darkness in A. palmata involving chaperone and antioxidant up-regulation, growth arrest, and metabolic modifications. As these responses were also measured during thermal stress, our results suggest that different stressors may share common bleaching mechanisms. Furthermore, our results point to ER stress as a critical cellular event involved in darkness-specific (and possibly more general) molecular bleaching mechanisms. On the other hand, we identified a meager transcriptomic response to darkness in M. faveolata, where gene expression differences between host colonies and/or sampling locations were greater than differences between control and stressed fragments. To this end, we discuss the importance of factors related to host genotype, Symbiodinium genotype, and the abiotic environment that influence host gene expression and thereby can hinder an investigator’s ability to measure gene expression during a condition of interest.
Project description:A mutualistic relationship between reef-building corals and endosymbiotic algae (Symbiodinium spp.) forms the basis for the existence of coral reefs. Genotyping tools for Symbiodinium spp. have added a new level of complexity to studies concerning cnidarian growth, nutrient acquisition, and stress. For example, the response of the coral holobiont to thermal stress is connected to the host-Symbiodinium genotypic combination, as different partnerships can have different bleaching susceptibilities. If, and to what extent, differences in algal symbiont clade contents can exert effects on the coral host transcriptome is currently unknown. In this study, we monitored algal physiological parameters and profiled the coral host transcriptional responses in acclimated, thermally stressed, and recovered coral fragments using a custom cDNA gene expression microarray. Combining these analyses with results from algal and host genotyping revealed a striking symbiont effect on both the acclimated coral host transcriptome and the magnitude of the thermal stress response. This is the first study that links coral host transcriptomic patterns to the clade content of their algal symbiont community. Our data provide a critical step to elucidating the molecular basis of the apparent variability seen among different coral-algal partnerships.
Project description:Coral bleaching occurs in response to numerous abiotic stressors, the ecologically most relevant of which is hyperthermic stress due to increasing seawater temperatures. Bleaching events can span large geographic areas and are currently a potent threat to coral reefs worldwide. Much effort has been focused on understanding the molecular and cellular events underlying bleaching, and these studies have mainly utilized heat and light stress regimes. In an effort to determine whether different stressors share common bleaching mechanisms, we used cDNA microarrays for the corals Acropora palmata and Montastraea faveolata (containing > 10,000 features) to measure differential gene expression during darkness stress. This is the first coral microarray experiment aimed at darkness stress, and the first for these species to interrogate gene expression at such a large scale. Our results reveal a striking transcriptomic response to darkness in A. palmata involving chaperone and antioxidant up-regulation, growth arrest, and metabolic modifications. As these responses were also measured during thermal stress, our results suggest that different stressors may share common bleaching mechanisms. Furthermore, our results point to ER stress as a critical cellular event involved in darkness-specific (and possibly more general) molecular bleaching mechanisms. On the other hand, we identified a meager transcriptomic response to darkness in M. faveolata where gene expression differences between host colonies and/or sampling locations were greater than differences between control and stressed fragments. To this end, we discuss the importance of factors related to host genotype, Symbiodinium genotype, and the abiotic environment that influence host gene expression and thereby can hinder an investigator’s ability to measure gene expression during a condition of interest. We employed a reference design where all control and dark-stressed samples were compared to a pooled reference aRNA sample composed of aRNA from all fragments. Since all RNA samples were compared to the reference sample, direct comparisons of gene expression across all time points and conditions can be performed.