PUVEREL S. 2004 - The Scleractinian coral biomineralization, organic matrix and transport of ions study. PhD these. Nice Sophia-Antipolis University. 178 p.

ABSTRACT

Biominerals are mineral structures made by organisms that are very widespread in the living world. In Scleractinian corals, biomineralization leads to the formation of an exoskeleton composed of aragonitic calcium carbonate. As in all biominerals, the mineralization process is controlled by an organic fraction called organic matrix and requires calcium and bicarbonate transport towards the mineralization site. This work focuses on these two aspects of the biomineralization process in Scleractinian corals.
Using polyclonal antibodies raised against the organic matrix extracted from the coral exoskeleton, we showed that coral biomineralization is a biologically-controlled process and that the calicoblastic ectoderm is the site of organic matrix synthesis and secretion. Moreover, we studied matrix proteins from the corals Stylophora pistillata and Pavona cactus, and obtained six microsequences which will be used to characterize these proteins. In addition, by labelling coral organic matrix proteins with radioactive amino acids, we showed the presence of low molecular weight proteins within a biomineral. We also observed the expression of a BMP (Bone Morphogenetic Protein) in the adult coral Acropora sp. and have begun to study the potential role of this protein in coral skeletal formation. Concerning the supply of ions essential to biomineralization, we investigated the molecular mechanisms of calcium transport. We characterized a calcium-ATPase that is located in the calicoblastic ectoderm, suggesting that this protein is involved in calcium transport toward the mineralization site.

Key-words: biomineralization / organic matrix / coral / exoskeleton / calicoblastic ectoderm / calcium-ATPase.