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Identifying Genes Associated with the Molecular Scleractinian Coral Calcification Process (Stylophora pistillata study case)

ABSTRACT: Increasing seawater’s calcium concentration has shown to increase reef building (scleractinian) coral’s calcification rates. In this way the expression of the genes that are associated with the calcification process also altered and, thus can be identified. Needless to say that the overall gene repertoire that participate in the coral calcification process and its molecular mechanisms have not yet been revealed, although sporadic genes that are related to the process have been discovered and investigated. In this study, nubbins of the Red Sea scleractinian coral, Stylophora pistillata were treated with increased calcium concentrations seawater (addition of 100 gm/L) and the genes that have been up-regulated were compared to the genes expression profile of corals with natural seawater calcium concentration. Measurements of AT were taken at mid-day (11:00) and in nighttime (23:00), to record the calcification rates of coral individuals under normal and increased calcium seawater concentrations. In order to reveal the gene involved in the calcification process, S. pistillata fragments of normal and of increased calcium concentrations were sampled for microarray RNA transcriptional profiling at two time-points (mid-day and nighttime).Results of this study have revealed that Smad genes may play a role in the coral skeletal growth apparatus. This study show that the calcification molecular mechanism is conserved Among identified genes are large group of genes that are characterized in the TGF-b/BMP signal transduction pathways which have been revealed in other organisms to participate in bone and cartilage tissue development molecular processes.

ORGANISM(S): Stylophora pistillata

PROVIDER: GSE87159 | GEO | 2017/06/29

SECONDARY ACCESSION(S): PRJNA343739

REPOSITORIES: GEO

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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:The process of calcium carbonate biomineralization has arisen multiple times during metazoan evolution. In the phylum Cnidaria, biomineralization has mostly been studied in the subclass Hexacorallia (i.e. stony corals) in comparison to the subclass Octocorallia (i.e. red corals); the two diverged approximately 600 million years ago. The precious Mediterranean red coral, Corallium rubrum, is an octocorallian species, which produces two distinct high-magnesium calcite biominerals, the axial skeleton and the sclerites. In order to gain insight into the red coral biomineralization process and cnidarian biomineralization evolution, we studied the protein repertoire forming the organic matrix (OM) of its two biominerals. We combined High-Resolution Mass Spectrometry and transcriptome analysis to study the OM composition of the axial skeleton and the sclerites. We identified a total of 102 OM proteins, 52 are shared between the two red coral biominerals with scleritin being the most abundant protein in each fraction. Contrary to reef building corals, the red coral is collagen-rich (10 collagen-like proteins). Agrin-like glycoproteins and proteins with sugar-binding domains are also predominant. Twenty-seven and 23 proteins were uniquely assigned to the axial skeleton and the sclerites, respectively. Their inferred regulatory function suggests that the difference between the two biominerals rather relies on the modeling of the matrix network than on specific structural components. At least one OM component appears to have been horizontally transferred from prokaryotes early during Octocorallia evolution. Our results support the view that calcification of the red coral axial skeleton likely represents a secondary calcification of an ancestral gorgonian horny axis. In addition, the comparison with stony coral skeletomes highlighted the low proportion of similar proteins between the biomineral OMs of hexacorallian and octocorallian corals, suggesting an independent acquisition of calcification in anthozoans.

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Identifying Genes Associated with the Molecular Scleractinian Coral Calcification Process (Stylophora pistillata study case)

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