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:Thermal history plays a role in the response of corals to subsequent heat stress. Prior heat stress can have a profound impact on later thermal tolerance, but the mechanism for this plasticity is not clear. The understanding of gene expression changes behind physiological acclimatization is critical in forecasts of coral health in impending climate change scenarios. Acropora millepora fragments were preconditioned to sublethal bleaching threshold stress for a period of 10 days; this prestress conferred bleaching resistance in subsequent thermal challenge, in which non-preconditioned coral bleached. Using microarrays, we analyze the transcriptomes of the coral host, comparing the bleaching-resistant preconditioned treatment to non-preconditioned and control treatments.
Project description:Thermal history plays a role in the response of corals to subsequent heat stress. Prior heat stress can have a profound impact on later thermal tolerance, but the mechanism for this plasticity is not clear. The understanding of gene expression changes behind physiological acclimatization is critical in forecasts of coral health in impending climate change scenarios. Acropora millepora fragments were preconditioned to sublethal bleaching threshold stress for a period of 10 days; this prestress conferred bleaching resistance in subsequent thermal challenge, in which non-preconditioned coral bleached. Using microarrays, we analyze the transcriptomes of the coral host, comparing the bleaching-resistant preconditioned treatment to non-preconditioned and control treatments. This experiment compared host gene expression of Acropora millepora across control, non-preconditioned, and preconditioned treatments. Fragments were sampled prior to preconditioning (Day 4), following 10 days of thermal preconditioning (Day 20), and after two (Day 23), four (Day 25), and eight days (Day 29) of 31M-BM-0C thermal challenge. The analysis implements 45 arrays, representing 5 sampling points of three treatments (n=3).
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: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.
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.
Project description:Abstract The coral–dinoflagellate symbiosis is increasingly disrupted by global and local anthropogenic stressors. Coral bleaching is primarily a result of high sea surface temperatures, while eutrophication is associated with reef ecosystem degradation. Excess inorganic nitrogen relative to phosphate has been proposed to directly sensitise corals to thermal bleaching and accelerate reef decline. We assessed the proteomic response of the dinoflagellate coral symbiont Symbiodinium microadriaticum to elevated temperatures under multiple nutrient conditions by mass spectrometry. Elevated temperatures resulted in reductions of many chloroplast proteins, particularly light-harvesting complexes, with simultaneous increases in chaperone proteins. N:P imbalance had a larger effect on the proteome than temperature, but the biological processes and proteins responding to each stressor largely overlapped. The proteomes were highly similar at low N:P ratios but were strongly affected by phosphate starvation. High N:P ratios inhibited cell division, reflected by changes in proteins involved in protein translation. Imbalanced N:P did not increase sensitivity to high temperatures as measured by physiological means; however, imbalanced N:P strongly upregulated cell redox homeostasis proteins at high temperatures. As redox balance is critical during thermal bleaching, these data provide insight into the mechanisms of cellular responses to thermal and multiple stresses in the coral–dinoflagellate symbiosis.