Project description:Since the discovery of Chromera velia as a novel coral-associated microalga, this organism has attracted interest because of its unique evolutionary position between the photosynthetic dinoflagellates and the parasitic apicomplexans. The nature of the relationship between Chromera and its coral host is controversial. Is it a mutualism, from which both participants benefit, or is Chromera a parasite, harming its host? To better understand the interaction, larvae of the common Indo-Pacific reef-building coral Acropora digitifera were experimentally infected with Chromera and the impact on the host transcriptome assessed at 4, 12, and 48 h post-infection using Illumina RNA-Seq technology. The transcriptomic response of the coral to Chromera was complex and implies that host immunity is strongly suppressed, and both phagosome maturation and the apoptotic machinery modified. These responses differ markedly from those described for infection with a competent strain of the coral symbiont Symbiodinium, instead resembling those of vertebrate hosts to parasites and/or pathogens such as Mycobacterium tuberculosis. Consistent with ecological studies suggesting that the association may be accidental, the transcriptional response of A. digitifera larvae leads us to conclude that Chromera is more likely to be a coral parasite, commensal, or accidental bystander, but certainly not a beneficial mutualist
Project description:Coral reefs are declining globally. Temperature anomalies disrupt coral-algal symbioses at the molecular level, causing bleaching and mortality events. In terrestrial mutualisms, diversity in pairings of host and symbiont individuals (genotypes) results in ecologically and evolutionarily relevant stress response differences. The extent to which such intraspecific diversity provides functional variation in coral-algal systems is unknown. Here we assessed functional diversity among unique pairings of coral and algal individuals (holobionts). We targeted six genetically distinct Acropora palmata coral colonies that all associated with a single, clonal Symbiodinium ‘fitti’ strain in a natural common garden. No other species of algae or other strains of S. ‘fitti’ could be detected in host tissues. When colony branches were experimentally exposed to cold stress, host genotype influenced the photochemical efficiency of the symbiont strain, buffering the stress response to varying degrees. Gene expression differences among host individuals with buffered vs. non-buffered symbiont responses included biochemical pathways that mediate iron availability and oxygen stress signaling—critical components of molecular interactions with photosynthetic symbionts. Spawning patterns among hosts reflected symbiont performance differences under stress. These data are some of the first to indicate that genetic interactions below the species level affect coral holobiont performance. Intraspecific diversity serves as an important but overlooked source of physiological variation in this system, contributing raw material available to natural selection. Note: in the final publication, only ambient and cold treatments are discussed, but there was an additional hot treatment for each genotype at 34C. Most colonies expired after 6 hours, so PAM data could not be collected. The microarray data from 3.5 hours are included here.
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. Acropora palmata Samples: Three biological replicates of pooled larvae from each species and condition (i.e. untreated control, inoculated with competent Symbiodinium strain, inoculated with incompetent Symbiodinium strain) for both time points were hybridized against a pooled reference. Pooled references were constructed by combining equal amounts of aRNA from all control samples from A. palmata. References were labeled with Cy3, samples with Cy5. Montastraea faveolata Samples: Three biological replicates of pooled larvae from each species and condition (i.e. untreated control, inoculated with competent Symbiodinium strain, inoculated with incompetent Symbiodinium strain) for both time points were hybridized against a pooled reference. Pooled references were constructed by combining equal amounts of aRNA from all control samples from M. faveolata. References were labeled with Cy3, samples with Cy5. Symbiodinium sp. CassKB8: competent strain Symbiodinium sp. EL1: incompetent strain Symbiodinium sp. Mf1.05b: competent strain
Project description:Here we report the first recovery, sequencing, and identification of fossil biomineral proteins from a Pleistocene invertebrate. Fossils of the Caribbean stony coral Orbicella annularis retain total hydrolyzable amino acids of a similar composition to extracts from modern O. annularis skeletons and ~10% of the modern skeletal proteome was sequenced by LC-MS/MS over multiple trials in the best-preserved fossil coral specimen. The data are rich in acidic amino acids such as aspartate and glutamate typical of skeletal proteins, and one of the four sequenced fossil proteins, a highly acidic protein, has been previously characterized in modern coral skeletons. A combination of degradation, or amino acid racemization inhibition of trypsin digestion, appears to limit greater recovery. Nevertheless, our workflow determines optimal samples for effective sequencing of fossil coral proteins, allowing comparison of modern and fossil invertebrate protein sequences, and will likely lead to further improvements of the methods. Sequencing of endogenous organic molecules in fossil biominerals provides an ancient record of composition, potentially clarifying evolutionary changes and biotic responses to paleoenvironments.
Project description:Short title: Coral Meta-Transcriptomics Reveal Pollutant Stress Background: Corals represent symbiotic meta-organisms that require harmonization among the coral animal, photosynthetic zooxanthellae and associated microbes to survive environmental stresses. We investigated integrated-responses among coral and zooxanthellae in the scleractinian coral Acropora formosa in response to an emerging marine pollutant, the munitions constituent, 1,3,5-trinitro-1,3,5 triazine (RDX; 5 day exposures to 0 (control), 0.5, 0.9, 1.8, 3.7, and 7.2 mg/L, measured in seawater). Results: RDX accumulated readily in coral soft tissues with bioconcentration factors ranging from 1.1 to 1.5). Next-generation sequencing of a normalized meta-transcriptomic library developed for the eukaryotic components of the A. formosa coral holobiont was leveraged to conduct microarray-based global transcript expression analysis of integrated coral / zooxanthellae responses to the RDX exposure. Total differentially expressed transcripts (DET) increased with increasing RDX exposure concentrations as did the proportion of zooxanthellae DET relative to the coral animal. Transcriptional responses in the coral demonstrated higher sensitivity to RDX compared to zooxanthellae where increased expression of gene transcripts coding xenobiotic detoxification mechanisms (ie. cytochrome P450 and UDP glucuronosyltransferase 2) were initiated at the lowest exposure concentration. Increased expression of these detoxification mechanisms was sustained at higher RDX concentrations as well as production of a physical barrier to exposure through a 40% increase in mucocyte density at the maximum RDX exposure. At and above the 1.8 mg/L exposure concentration, DET coding for genes involved in central energy metabolism, including photosynthesis, glycolysis and electron-transport functions, were decreased in zooxanthellae although preliminary data indicated that zooxanthellae densities were not affected. In contrast, significantly increased transcript expression for genes involved in cellular energy production including glycolysis and electron-transport pathways was observed in the coral animal. Conclusions: Transcriptional network analysis for central energy metabolism demonstrated highly correlated responses to RDX among the coral animal and zooxanthellae indicative of potential compensatory responses to lost photosynthetic potential within the holobiont. These observations underscore the potential for complex integrated responses to RDX exposure among species comprising the coral holobiont and highlight the need to understand holobiont-species interactions to accurately assess pollutant impacts.
Project description:Here we report the first recovery, sequencing, and identification of fossil biomineral proteins from a Pleistocene invertebrate. Fossils of the Caribbean stony coral Orbicella annularis retain total hydrolyzable amino acids of a similar composition to extracts from modern O. annularis skeletons and ~10% of the modern skeletal proteome was sequenced by LC-MS/MS over multiple trials in the best-preserved fossil coral specimen. The data are rich in acidic amino acids such as aspartate and glutamate typical of skeletal proteins, and one of the four sequenced fossil proteins, a highly acidic protein, has been previously characterized in modern coral skeletons. A combination of degradation, or amino acid racemization inhibition of trypsin digestion, appears to limit greater recovery. Nevertheless, our workflow determines optimal samples for effective sequencing of fossil coral proteins, allowing comparison of modern and fossil invertebrate protein sequences, and will likely lead to further improvements of the methods. Sequencing of endogenous organic mand biotic responses to paleoenvironments.
Project description:The bacterial pathogen Vibrio coralliilyticus infects a variety of marine organisms globally and causes early onset of disease in multiple coral species. The etiology of coral disease and relative pathogenicity of V. coralliilyticus strains is well-documented, but the mechanisms of V. coralliilyticus coral colonization, virulence factor production, and interactions with coral microbiome are understudied. Many virulence factors responsible for pathogenic behaviors are controlled through a density-dependent, bacterial communication system called quorum sensing (QS). In other Vibrio species, behaviors like bioluminescence, biofilm formation, toxin secretion, and protease production are controlled via the master quorum sensing transcriptional regulator called LuxR/HapR. Comparative genomics indicated that V. coralliilyticus genomes share high sequence identity for most of the QS signaling and regulatory components identified in other Vibrio species. Here, we characterize active components of the V. coralliilyticus QS system and identify the VcpR (LuxR/HapR homolog) regulons in two strains with distinct infection etiologies. We show that VcpR transcription is dependent on signaling by autoinducer AI-2, whereas we were unable to detect production of acyl-homoserine lactone autoinducers. The VcpR regulator controls expression of >200 genes in both the type strain BAA-450 and isolate OCN008, including two genes encoding proteases (VcpA and VcpB) known to impact coral infection. In both isolates, VcpR activates the expression of Type VI Secretion System genes from both systems 1 and 2, which results in interbacterial competition and killing of prey bacteria. We conclude that the QS system in V. coralliilyticus is active and controls expression of genes involved in relevant bacterial behaviors that may influence coral infection.
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. Approximately 21 species of coral, including both Endangered Species Act-listed and the primary reef-building species, have displayed tissue loss lesions which often result in whole colony mortality [Stony Coral Tissue Loss Disease (SCTLD)]. Determining the causative agent(s) of coral disease relies on a multidisciplinary approach since the causation may be a combination of abiotic, microbial or viral agents. Metaproteomics was used to survey changes in the molecular landscape in the coral holobiont with the goal of providing useful information not only in diagnosis, but for prediction and prognosis. Specifically, in the case of SCTLD, defining molecular changes in the coral holobiont will help define disease progression and aid in identifying the causative agent by clearly defining traits of disease progression shared across affected species. Using samples from nine coral species (46 samples total; those appearing healthy, n = 23, and diseased, n = 23), analysis of the coral and its associated microbiome were performed using bottom-up proteomics. Ongoing analysis (including improving coral holobiont genome-based search space) will demonstrate the utility of this approach and help define improved future experiments.