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1 March 2007 Identification of a Novel Yolk Protein in the Hermatypic Coral Galaxea fascicularis
Hideki Hayakawa, Tadashi Andoh, Toshiki Watanabe
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The reef-building (or hermatypic) coral Galaxea fascicularis (Anthozoa, Hexacorallia, Scleractinia) has an annual reproductive cycle. Females of G. fascicularis release packages (or ‘bundles’) of eggs for external fertilization, whereas male individuals form bundles consisting of sperm and infertile ‘pseudo-eggs’ that are thought to confer buoyancy to the male bundle. In the egg of G. fascicularis, four proteins (GfEP-1 to 4) were found to be stored in high abundance, and three of them (GfEP-1, 2 and 3) are generated by processing of a vitellogenin (Vg)-like precursor. In the present study, a cDNA encoding GfEP-4 was cloned and its sequence determined (GenBank/EMBL/DDBJ accession no. AB259859). The amino acid sequence of this protein does not exhibit similarity to known proteins, including Vgs or other yolk proteins found in some invertebrates. The expression of GfEP-4 mRNA was observed in females, and also in the majority of males examined, although expression levels were lower than in females. The GfEP-4 protein was detected in pseudo-eggs, where its concentration was 20–100 times lower than in eggs. In contrast, GfEP-1, 2 and 3 were not detected in pseudo-eggs. A protein (28 kDa) which cross-reacted with anti-GfEP-4 antibodies was detected in eggs of the coral Montipora digitata, suggesting the possibility that homologs of this protein are present in the eggs of other scleractinian corals.

Hideki Hayakawa, Tadashi Andoh, and Toshiki Watanabe "Identification of a Novel Yolk Protein in the Hermatypic Coral Galaxea fascicularis," Zoological Science 24(3), 249-255, (1 March 2007).
Received: 7 June 2006; Accepted: 1 October 2006; Published: 1 March 2007

Coral reef
yolk protein
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