Expression of a putative precursor mRNA for sperm-activating peptide I in accessory cells of the ovary in the sea urchin Hemicentrotus pulcherrimus.

A cDNA clone encoding egg jelly peptide, SAP-I (Gly-Phe-Asp-Leu-Asn-Gly-Gly-Gly-Val-Gly), was isolated from a Hemicentrotus pulcherrimus ovary cDNA library and its nucleotide sequence was determined. The cDNA was 1282 by long and an open reading frame predicted a protein of 334 amino acids containing 5 SAP-I and 7 SAP-I-like decapeptides, each separated by a single lysine residue. The cDNA hybridized to two species of mRNA (1.3 kb and 2.0 kb) from H. pulcherrimus ovaries. Northern blot analysis showed that the 1.3 kb transcripts appeared in ovaries collected from November to April and the 2.0 kb transcripts were detected only in ovaries collected in January. An expression study of the SAM precursor gene, by in situ hybridization with a non-radioactive RNA probe synthesized using the 1.3 kb cDNA as template, demonstrated that abundant SAM precursor transcripts were expressed in the accessory cells, but not in the growing oocytes.