Project description:Coral reefs are based on the symbiotic relationship between corals and photosynthetic dinoflagellates of the genus Symbiodinium. We followed gene expression of coral larvae of Acropora palmata and Montastraea faveolata after exposure to Symbiodinium strains that differed in their ability to establish symbioses. We show that the coral host transcriptome remains almost unchanged during infection by competent symbionts, but is massively altered by symbionts that fail to establish symbioses. Our data suggest that successful coral-algal symbioses depend mainly on the symbionts' ability to enter the host in a stealth manner rather than a more active response from the coral host.
Project description:Scleractinian corals are the major builders of the complex structural framework of coral reefs. They live in tropical waters around the globe where they are frequently exposed to potentially harmful ultraviolet radiation (UVR). Coral eggs and early embryonic stages are thought to be the most sensitive life stages of corals to UVR given that they are highly buoyant and remain near the sea surface for prolonged periods of time. Here we analyzed gene expression changes in different larval stages of the Caribbean coral Montastraea faveolata to natural levels of UVR using high-density cDNA microarrays (10,930 clones). We found that larvae exhibit low sensitivity to natural levels of UVR during most time points analyzed as reflected by comparatively few transcriptomic changes in response to UVR. However, we identified a time window of high UVR sensitivity that coincides with the motile planula stage and the onset of larval competence. These processes have been shown to be affected upon UVR exposure, and the transcriptional changes we identified explain these observations well. Our analysis of differentially expressed genes indicates that UVR induces a stress response and affects the expression of neurogenesis-related genes that can be linked to swimming and settlement behavior at later stages. Taken together, our study provides further data to the impact of natural levels of UVR on coral larvae. Furthermore, our results might allow a better prediction of settlement and recruitment rates after coral spawning events based on UVR climate data.
2011-05-15 | GSE24949 | GEO
Project description:Plankton diversity on the coral reefs of South China Sea
Project description:Florida’s coral reefs are currently experiencing a multi-year disease-related mortality event, that has resulted in massive die-offs in multiple coral species. Coral monitoring data and disease prevention/treatment efforts from recent years have identified individual Orbicella faveolata that possess high, moderate, or low resistance to stony coral tissue loss disease (SCTLD). Ninety samples of high, moderate, or low SCTLD resistance were collected from 3 reefs for bottom-up LC-MS/MS analysis (n=30 for each resistance category).
Project description:Background Coral reefs are expected to be severely impacted by rising seawater temperatures associated with climate change. This study used cDNA microarrays to investigate transcriptional effects of thermal stress in embryos of the coral Montastraea faveolata. Embryos were exposed to 27.5C, 29.0C, and 31.5C directly after fertilization. Differences in gene expression were measured after 12 and 48 hours. Results Analysis of differentially expressed genes indicated that increased temperatures may lead to oxidative stress, apoptosis, and a structural reconfiguration of the cytoskeletal network. Metabolic processes were downregulated, and the action of histones and zinc finger-containing proteins may have played a role in the long-term regulation upon heat stress. Conclusions Embryos responded differently depending on exposure time and temperature level. Embryos showed expression of stress-related genes already at a temperature of 29.0C, but seemed to be able to counteract the initial response over time. By contrast, embryos at 31.5C displayed continuous expression of stress genes. The genes that played a role in the response to elevated temperatures consisted of both highly conserved and coral-specific genes. These genes might serve as a basis for research into coral-specific adaptations to stress responses and global climate change.
Project description:Naval training exercises involving live ordnance can introduce munitions constituents (MCs) such as 1,3,5-trinitro-1,3,5 triazine (RDX) into the marine environment posing a potential environmental hazard to reef organisms, including corals. We developed a bioinformatic infrastructure and high-density microarray for a coral consortium and assessed the effects of RDX bioaccumulation on gene expression related to coral and endosymbiont health in the reef building coral (Acropora formosa). High-throughput sequencing and assembly of the transcriptomes for A. formosa and all eukaryotic endosymbionts yielded 189,616 unique sequences and 25,003 significant functional matches to protein-coding genes. Functional annotation and metabolic pathway associations were also developed. The bioinformatics base was transitioned to custom 15,000 probe microarrays that were used to assess RDX effects on gene expression in the A. formosa coral consortium. Coral fragments were exposed to RDX (0.5, 1, 2, 4, and 8 mg/L) for 5d in a controlled laboratory experiment. RDX readily accumulated into coral tissues; however, bioconcentration was minimal (bioconcentration factor = 1.09-1.50). RDX caused no significant changes in zooxanthellae tissue densities, however a significant (p<0.05) 40% increase in mucocytes was observed in the 8 mg/L exposure indicating a mucosal protective response to RDX exposure. Investigation of T-RFLP profiles indicated significant differences in bacterial community composition inhabiting the coral surface microlayer of Acropora sp. between control and RDX-exposed coral as among exposure concentrations. Differential expression of transcripts increased with increasing RDX concentration where 126, 195 and 272 transcripts were differentially expressed in the 0.5, 2.0 and 8 mg/L RDX treatments, respectively. The commonality in differentially expressed transcripts (DET) among exposure concentrations ranged from 9.9 to 29.0% where the lowest commonality was observed between the most disparate RDX exposure concentrations. Increasing RDX concentrations caused an increasing proportion of the number of transcripts differentially expressed in symbionts relative to corals. Further, a trend toward decreased transcript expression in symbionts in response to increasing RDX concentration was observed where 20.0% of differentially expressed transcripts had decreased expression at the 0.5 mg/L concentration, whereas 80.4% had decreased expression at the 8 mg/L concentration. Investigation of KEGG orthology for DET indicated potential impacts of RDX on a variety of molecular pathways, predominantly in endosymbionts compared to the coral host. Prominent effects of RDX exposure on pathways included enrichment of DET involved in carbohydrate metabolism, amino acid metabolism, energy metabolism, lipid metabolism, metabolism of cofactors and vitamins, environmental information processing and cellular processes. Fragments of the living branched coral Acropora formosa were obtained from Oceans, Reefs and Aquaria (http://www.orafarm.com). Ten gallon aquaria were used to expose 5 coral fragments to control or RDX exposure conditions (0.49, 0.93, 1.77, 3.67 and 7.18 mg/L, measured concentrations). The microarray hybridization experiment included 3 biological replicates for the 0.5, 2, and 8 mg/L RDX conditions and 4 biological replicates for the control.
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.