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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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Molecular composition of the skeletal organic matrix from A. millepora.(A) Analysis of electrophoresis on gel after AgNO3 staining.(B) PVDF membrane revealed by autoradiography with 45Ca, calmodulin (CaM)was used as positive control. (C) Infrared absorption spectra of ASM and AIM fractions with assignment of the main peaks. MM – Molecular marker, ASM – Acid soluble matrix, AIM – Acid insoluble matrix.
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pone-0097454-g002: Molecular composition of the skeletal organic matrix from A. millepora.(A) Analysis of electrophoresis on gel after AgNO3 staining.(B) PVDF membrane revealed by autoradiography with 45Ca, calmodulin (CaM)was used as positive control. (C) Infrared absorption spectra of ASM and AIM fractions with assignment of the main peaks. MM – Molecular marker, ASM – Acid soluble matrix, AIM – Acid insoluble matrix.

Mentions: The extraction of the skeletal organic matrix from fine skeleton powder yielded 0.034±0.01% of ASM and 0.23±0.03% of AIM (w/w of the dry powder), corresponding to a AIM/ASM ratio between 6 and 7. The analysis of the ASM on mono-dimensional gel (Figure 2 A) stained with AgNO3 revealed a profile comprising 3 main diffuse bands at approximately 120, 90 and 64 kDa in a smear of polydisperse macromolecules that stains preferentially around high molecular weights. Between 20 and 40 kDa, the ASM is hardly stained or tends to stain negatively. On AgNO3-stained gel, the profile of the AIM is uniformly stained and shows exclusively polydisperse molecules. Both fractions exhibit a calcium-binding ability, when labeled with 45Ca (Figure 2 B). In the ASM, the 64 kDa band shows a strong Ca-binding signal while two other non discrete signals are detected for high (above 170 kDa) and low (below 17 kDa) molecular weights components. In addition, the two other discrete bands (at 120 and 90 kDa respectively) exhibit fainter Ca-binding signals. In the AIM, only a significant signal is observed at high molecular weights (above ∼172 kDa). This signal is concentrated in a short smear and in two distinct discrete bands, which in turn are not stained with silver nitrate.


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)

Molecular composition of the skeletal organic matrix from A. millepora.(A) Analysis of electrophoresis on gel after AgNO3 staining.(B) PVDF membrane revealed by autoradiography with 45Ca, calmodulin (CaM)was used as positive control. (C) Infrared absorption spectra of ASM and AIM fractions with assignment of the main peaks. MM – Molecular marker, ASM – Acid soluble matrix, AIM – Acid insoluble matrix.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0097454-g002: Molecular composition of the skeletal organic matrix from A. millepora.(A) Analysis of electrophoresis on gel after AgNO3 staining.(B) PVDF membrane revealed by autoradiography with 45Ca, calmodulin (CaM)was used as positive control. (C) Infrared absorption spectra of ASM and AIM fractions with assignment of the main peaks. MM – Molecular marker, ASM – Acid soluble matrix, AIM – Acid insoluble matrix.
Mentions: The extraction of the skeletal organic matrix from fine skeleton powder yielded 0.034±0.01% of ASM and 0.23±0.03% of AIM (w/w of the dry powder), corresponding to a AIM/ASM ratio between 6 and 7. The analysis of the ASM on mono-dimensional gel (Figure 2 A) stained with AgNO3 revealed a profile comprising 3 main diffuse bands at approximately 120, 90 and 64 kDa in a smear of polydisperse macromolecules that stains preferentially around high molecular weights. Between 20 and 40 kDa, the ASM is hardly stained or tends to stain negatively. On AgNO3-stained gel, the profile of the AIM is uniformly stained and shows exclusively polydisperse molecules. Both fractions exhibit a calcium-binding ability, when labeled with 45Ca (Figure 2 B). In the ASM, the 64 kDa band shows a strong Ca-binding signal while two other non discrete signals are detected for high (above 170 kDa) and low (below 17 kDa) molecular weights components. In addition, the two other discrete bands (at 120 and 90 kDa respectively) exhibit fainter Ca-binding signals. In the AIM, only a significant signal is observed at high molecular weights (above ∼172 kDa). This signal is concentrated in a short smear and in two distinct discrete bands, which in turn are not stained with silver nitrate.

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