Relationship Between Vitellogenin and Vitellin in a Marine Shrimp (Penaeus semisulcatus) and Molecular Characterization of Vitellogenin Complementary DNAs1

Apr 4, 2003Biology of reproduction

Link between egg yolk proteins and genetic description of egg yolk precursor in a marine shrimp

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Abstract

Two cDNAs of 7920 and 2068 nucleotides were sequenced for vitellogenin from the ovary of Penaeus semisulcatus.

Vitellogenin (VTG) cDNA from the hepatopancreas was similar to that from the ovary.
A VTG gene was found in males, but large transcripts were only detected in females.
mRNA expression patterns were associated with ovarian development stages and the molt cycle.
VTG and vitellin (VT) apoproteins were shown to consist of two and three major subunits, respectively.
Cleavage sites for specific endoproteases were identified in VTG and VT subunits.

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The source of yolk proteins in crustacean ovaries has been the subject of controversy for several decades, and both extraovarian and intraovarian synthesized proteins have been implicated. To offer a new insight into the relationship of vitellogenin (VTG) and vitellin (VT), a comparison of extraovarian VTG and ovarian VT of the marine shrimp Penaeus semisulcatus was performed at the protein and cDNA levels. Two cDNAs (7920 and 2068 nucleotides [nt]) were sequenced for VTG from the ovary and one cDNA (7920 nt) was sequenced from the hepatopancreas. VTG cDNA from hepatopancreas was similar to VTG cDNA from ovary. Although a VTG gene was also found in the males, approximately 7.8-kilobase transcripts were only detected in the ovary and hepatopancreas of females. The mRNA expression pattern was related to the stage of ovarian development and to the molt cycle, as determined by real-time polymerase chain reaction assay. VTG and VT apoproteins were composed of two and three major subunits, respectively, as shown by SDS-PAGE. N-terminal sequences of these subunits revealed the presence of a cleavage site at a consensus motif for a subtilisin-like endoprotease in VTG and VT and an additional cleavage site in VT revealed by an unidentified endoprotease. These results indicate that penaeid shrimps constitute a unique model for vitellogenesis, showing intraovarian gene expression and synthesis of yolk protein.

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Relationship Between Vitellogenin and Vitellin in a Marine Shrimp (Penaeus semisulcatus) and Molecular Characterization of Vitellogenin Complementary DNAs1

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