Project description:Two known settlement/metamorphosis inducing stimuli (crustose coralline algae, and ethanolic extract of crustose coralline algae) and one stimulus which just induces metamorphosis (LWamide) were used to stimulate competent planula larvae of the coral Acropora millepora. Samples were taken 0.5h, 4h and 12h post induction isolate the genes controlling settlement and metamorphosis in this coral.
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.
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:Monitoring microbial communities can aid in understanding the state of these habitats. Environmental DNA (eDNA) techniques provide efficient and comprehensive monitoring by capturing broader diversity. Besides structural profiling, eDNA methods allow the study of functional profiles, encompassing the genes within the microbial community. In this study, three methodologies were compared for functional profiling of microbial communities in estuarine and coastal sites in the Bay of Biscay. The methodologies included inference from 16S metabarcoding data using Tax4Fun, GeoChip microarrays, and shotgun metagenomics.
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. Gamete capture and larval rearing Montastraea faveolata gametes were captured and reared as described in Voolstra et al. 2009 (2009a). Briefly, gametes from 10 colonies were captured during a spawning event on the night of the 10th of September 2009 at approximately 22:00 hours using collecting nets attached to plastic enclosures at “La Bocana Chica” (20º50´N, 86º52´W) located in the “Parque Nacional Arrecife de Puerto Morelos”. Within 10 minutes the gametes were brought to the research vessel “Carybdea”, where they were placed in 5 µm filtered sea water (FSW), large zooplankton was removed, and the egg-sperm mixture was mixed gently to enhance the process of fertilization during transportation to the research station (Unidad Académica Puerto Morelos). After 1 hour, the egg-sperm mixture was repeatedly washed with 5 µm FSW to ensure that all unused sperm and remaining zooplankton were removed. The embryos were placed in round, bottomless, incubation bins fitted with 100 µm mesh, which were housed in abundant 5 µm FSW. Fertilization success, measured 6 hours after the washing procedure, was estimated at 95% by counting the number of eggs undergoing division as a proportion of the total number of eggs (dividing + non-dividing). Experimental procedure After 12 hours, the majority of the embryos were in the late blastula stage. A subsample of embryos was taken from different incubation bins and divided into twelve 1 liter containers with 5 µm FSW added to the brim. Each container held approximately 3,000 embryos. All of the containers were placed in 800 L fiber glass aquaria filled with flowing sea water and exposed to natural solar radiation from 9am to 3pm (6h) at 29ºC and 3.5% salinity. Six of the containers were placed under a sheet of 6mm thick Plexiglass G UVT that has a full width at half maximum (FWHM) at 282 nm and is therefore transparent to UVR. The other six containers were placed under a sheet of 4 mm thick Plexiglass G UF-3 that has a FWHM at 390 nm and is therefore opaque to UVR. At the end of the exposure period, the embryos were harvested and preserved in RNAlater (Ambion), placed at 4ºC for 24 hours to ensure infiltration of the fixative and frozen at -80ºC until further processing. The same exposure and fixation procedures were repeated on 36 hours old embryos (late gastrula stage), on 60 hours old non-motile, floating larvae, on 84 hours old motile planulae, and on 132 hours old planulae that are motile, diving, and ready for settlement.
Project description:Corals in nearshore marine environments are increasingly exposed to reduced water quality, which is the major local threat to coral reefs in Hawaii. Corals surviving in such conditions may have adapted to withstand sedimentation, pollutants, and other environmental stressors. Lobe coral (Porites lobata) populations from Maunalua Bay, Hawaii showed clear genetic differentiation along with distinct cellular protein expressions between the 'polluted, high-stress' nearshore site and the 'low-stress' offshore site. To understand the driving force of the observed genetic partitioning, reciprocal transplant and common-garden experiments were conducted using the nearshore and offshore colonies of P. lobata from Maunalua Bay to assess phenotypic differences between the two coral populations. Stress-related physiological and molecular responses were compared between the two populations. Proteomic responses highlighted the inherent differences in the cellular metabolic state and activities between the two populations under the same environmental conditions; nearshore corals did not significantly alter their proteome between the sites, while offshore corals responded to the nearshore transplantation with increased abundances of proteins associated with detoxification, antioxidant, and various metabolic processes. The response differences across multiple phenotypes suggest that the observed genetic partitioning was likely due to local adaptation.
Project description:Background: Anthozoan cnidarians are amongst the simplest animals at the tissue level of organization, but are surprisingly complex and vertebrate-like in terms of gene repertoire. As major components of tropical reef ecosystems, the stony corals are anthozoans of particular ecological significance. To better understand the molecular bases of both cnidarian development in general and coral-specific processes such as skeletogenesis and symbiont acquisition, microarray analysis was carried out through the period of early development – when skeletogenesis is initiated, and symbionts are first acquired. Methodology/ Principal Findings: Of approximately 5600 unique genes represented on the microarrays, 1084 were differentially expressed (P <0.05) in comparisons between four different stages of coral development, spanning key developmental transitions. Genes of likely relevance to the processes of settlement, metamorphosis, calcification and interaction with symbionts were characterised further and their spatial expression patterns investigated using whole-mount in situ hybridisation. Conclusions/Significance: This study is the first large-scale investigation of developmental gene expression for any cnidarian, and has provided candidate genes for key roles in many aspects of coral biology, including calcification, metamorphosis and symbiont uptake. One surprising finding is that some of these genes have clear counterparts in higher animals but are not present in the closely-related sea anemone Nematostella. A second conclusion is that coral-specific processes (i.e. traits which distinguish corals from their close relatives) may be analogous to similar processes in distantly related organisms. This first large-scale application of microarray analysis demonstrates the potential of this approach for investigating many aspects of coral biology, including the effects of stress and disease. Keywords: developmental