Equal contribution of hepatopancreas and ovary to the production of vitellogenin (PmVg1) transcripts in the tiger shrimp, Penaeus monodon

Abstract

Although the gene fragment and partial cDNA for the vitellogenin (Vg) of Penaeus monodon have been reported for several years, the complete gene sequence and full-length cDNA of this Vg has not been reported. Here we report the gene organization and cloning of the full-length cDNA of P. monodon Vg. Similar to the MeVg1 of M. ensis, the Vg gene of P. monodon (PmVg1) is confirmed to consist of 14 introns and 15 exons. Additionally, genomic DNAs that show high sequence identity to PmVg1 were isolated from a single shrimp. The result confirmed the existence of multiple Vg genes in P. monodon. PmVg cDNA is 7.8 kb in size and the deduced precursor is most similar to the Vg of Penaeus merguenesis (86% identity). Contrary to the previous report, similar levels of PmVg1 transcripts can be detected from the hepatopancreas and ovary suggesting that the ovary also plays a major role in the contribution of PmVg1 transcript during vitellogenesis. In shrimp at early vitellogenesis (i.e., GSI < 3%), the expression of PmVg1 in the ovary and hepatopancreas is low; the expression reached the maximum level in shrimp with GSI 4–8% and decreased in shrimp with GSI > 9%. Farnesoic acid and 20-hydroecdysone can cause a significant stimulation of PmVg1 expression in an in vitro hepatopancreas explant culture. In conclusion, vitellogenesis in P. monodon is most likely the result of the expression of multiple vitellogenin genes and the hepatopancreas and ovary contribute equally to the production of PmVg1 transcripts.