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The skeleton of the staghorn coral Acropora millepora: molecular and structural characterization.

Ramos-Silva P, Kaandorp J, Herbst F, Plasseraud L, Alcaraz G, Stern C, Corneillat M, Guichard N, Durlet C, Luquet G, Marin F - PLoS ONE (2014)

Bottom Line: Besides secreted proteins, there are a significant number of proteins with membrane attachment sites such as transmembrane domains and GPI anchors as well as proteins with integrin binding sites.Finally, we observe that the interaction of the acetic acid soluble SOM on the morphology of in vitro grown CaCO3 crystals is very pronounced when compared with the calcifying matrices of some mollusks.In light of these results, we wish to commend Acropora millepora as a model for biocalcification studies in scleractinians, from molecular and structural viewpoints.

View Article: PubMed Central - PubMed

Affiliation: UMR 6282 Biogéosciences, Université de Bourgogne, Dijon, France; Section Computational Science, Faculty of Science, University of Amsterdam, Amsterdam, The Netherlands.

ABSTRACT
The scleractinian coral Acropora millepora is one of the most studied species from the Great Barrier Reef. This species has been used to understand evolutionary, immune and developmental processes in cnidarians. It has also been subject of several ecological studies in order to elucidate reef responses to environmental changes such as temperature rise and ocean acidification (OA). In these contexts, several nucleic acid resources were made available. When combined to a recent proteomic analysis of the coral skeletal organic matrix (SOM), they enabled the identification of several skeletal matrix proteins, making A. millepora into an emerging model for biomineralization studies. Here we describe the skeletal microstructure of A. millepora skeleton, together with a functional and biochemical characterization of its occluded SOM that focuses on the protein and saccharidic moieties. The skeletal matrix proteins show a large range of isoelectric points, compositional patterns and signatures. Besides secreted proteins, there are a significant number of proteins with membrane attachment sites such as transmembrane domains and GPI anchors as well as proteins with integrin binding sites. These features show that the skeletal proteins must have strong adhesion properties in order to function in the calcifying space. Moreover this data suggest a molecular connection between the calcifying epithelium and the skeletal tissue during biocalcification. In terms of sugar moieties, the enrichment of the SOM in arabinose is striking, and the monosaccharide composition exhibits the same signature as that of mucus of acroporid corals. Finally, we observe that the interaction of the acetic acid soluble SOM on the morphology of in vitro grown CaCO3 crystals is very pronounced when compared with the calcifying matrices of some mollusks. In light of these results, we wish to commend Acropora millepora as a model for biocalcification studies in scleractinians, from molecular and structural viewpoints.

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Related in: MedlinePlus

Skeleton morphology and microstructure.(A) Skeletal fragments after treatment in NaOCl (5%, vol/vol) for 72 h prior to longitudinal and transversal cuts. Scanning electron microscopy images from the skeleton morphology: (B) Axial corallite, (C) Radial corallites, (D) Closer view into a radial corallite showing different septa. Polished and EDTA-etched sections from a transversal cut (E–G) and longitudinal cut (H–I). EMZ – early mineralization zone.
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pone-0097454-g001: Skeleton morphology and microstructure.(A) Skeletal fragments after treatment in NaOCl (5%, vol/vol) for 72 h prior to longitudinal and transversal cuts. Scanning electron microscopy images from the skeleton morphology: (B) Axial corallite, (C) Radial corallites, (D) Closer view into a radial corallite showing different septa. Polished and EDTA-etched sections from a transversal cut (E–G) and longitudinal cut (H–I). EMZ – early mineralization zone.

Mentions: Prior to further characterizations, the aragonitic nature of the skeleton of Acropora millepora was confirmed by Raman and FTIR spectra (Figure S1) in order to ensure the absence of recrystallization in calcite, or the presence of traces of vaterite. In addition, EDS spot analyses were performed on different points (transects, and points taken randomly, data not shown) for checking the elemental homogeneity of the skeleton. They confirmed that the atomic percentages of minor elements (Mg, Na, Sr, S) did not vary significantly, demonstrating that the skeletal parts were fresh from top to bottom and also in their diameter (see Figure 1 A). This check allowed us to assert with confidence that the fragments used for the subsequent matrix extraction were not submitted to detectable early diagenetic processes, affecting the mineral phase.


The skeleton of the staghorn coral Acropora millepora: molecular and structural characterization.

Ramos-Silva P, Kaandorp J, Herbst F, Plasseraud L, Alcaraz G, Stern C, Corneillat M, Guichard N, Durlet C, Luquet G, Marin F - PLoS ONE (2014)

Skeleton morphology and microstructure.(A) Skeletal fragments after treatment in NaOCl (5%, vol/vol) for 72 h prior to longitudinal and transversal cuts. Scanning electron microscopy images from the skeleton morphology: (B) Axial corallite, (C) Radial corallites, (D) Closer view into a radial corallite showing different septa. Polished and EDTA-etched sections from a transversal cut (E–G) and longitudinal cut (H–I). EMZ – early mineralization zone.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4043741&req=5

pone-0097454-g001: Skeleton morphology and microstructure.(A) Skeletal fragments after treatment in NaOCl (5%, vol/vol) for 72 h prior to longitudinal and transversal cuts. Scanning electron microscopy images from the skeleton morphology: (B) Axial corallite, (C) Radial corallites, (D) Closer view into a radial corallite showing different septa. Polished and EDTA-etched sections from a transversal cut (E–G) and longitudinal cut (H–I). EMZ – early mineralization zone.
Mentions: Prior to further characterizations, the aragonitic nature of the skeleton of Acropora millepora was confirmed by Raman and FTIR spectra (Figure S1) in order to ensure the absence of recrystallization in calcite, or the presence of traces of vaterite. In addition, EDS spot analyses were performed on different points (transects, and points taken randomly, data not shown) for checking the elemental homogeneity of the skeleton. They confirmed that the atomic percentages of minor elements (Mg, Na, Sr, S) did not vary significantly, demonstrating that the skeletal parts were fresh from top to bottom and also in their diameter (see Figure 1 A). This check allowed us to assert with confidence that the fragments used for the subsequent matrix extraction were not submitted to detectable early diagenetic processes, affecting the mineral phase.

Bottom Line: Besides secreted proteins, there are a significant number of proteins with membrane attachment sites such as transmembrane domains and GPI anchors as well as proteins with integrin binding sites.Finally, we observe that the interaction of the acetic acid soluble SOM on the morphology of in vitro grown CaCO3 crystals is very pronounced when compared with the calcifying matrices of some mollusks.In light of these results, we wish to commend Acropora millepora as a model for biocalcification studies in scleractinians, from molecular and structural viewpoints.

View Article: PubMed Central - PubMed

Affiliation: UMR 6282 Biogéosciences, Université de Bourgogne, Dijon, France; Section Computational Science, Faculty of Science, University of Amsterdam, Amsterdam, The Netherlands.

ABSTRACT
The scleractinian coral Acropora millepora is one of the most studied species from the Great Barrier Reef. This species has been used to understand evolutionary, immune and developmental processes in cnidarians. It has also been subject of several ecological studies in order to elucidate reef responses to environmental changes such as temperature rise and ocean acidification (OA). In these contexts, several nucleic acid resources were made available. When combined to a recent proteomic analysis of the coral skeletal organic matrix (SOM), they enabled the identification of several skeletal matrix proteins, making A. millepora into an emerging model for biomineralization studies. Here we describe the skeletal microstructure of A. millepora skeleton, together with a functional and biochemical characterization of its occluded SOM that focuses on the protein and saccharidic moieties. The skeletal matrix proteins show a large range of isoelectric points, compositional patterns and signatures. Besides secreted proteins, there are a significant number of proteins with membrane attachment sites such as transmembrane domains and GPI anchors as well as proteins with integrin binding sites. These features show that the skeletal proteins must have strong adhesion properties in order to function in the calcifying space. Moreover this data suggest a molecular connection between the calcifying epithelium and the skeletal tissue during biocalcification. In terms of sugar moieties, the enrichment of the SOM in arabinose is striking, and the monosaccharide composition exhibits the same signature as that of mucus of acroporid corals. Finally, we observe that the interaction of the acetic acid soluble SOM on the morphology of in vitro grown CaCO3 crystals is very pronounced when compared with the calcifying matrices of some mollusks. In light of these results, we wish to commend Acropora millepora as a model for biocalcification studies in scleractinians, from molecular and structural viewpoints.

Show MeSH
Related in: MedlinePlus