Isolation and characterization of progesterone receptor-related protein p23 (Pm-p23) differentially expressed during ovarian development of the giant tiger shrimp Penaeus monodon

A homologue of progesterone receptor-related protein p23 (Pm-p23) was isolated from EST analysis of the cDNA library established from vitellogenic ovaries of the giant tiger shrimp (Penaeus monodon). The full length cDNA of Pm-p23 was further characterized by RACE-PCR and it was 1943 bp, comprising an open reading frame (ORF) of 495 bp corresponding to 164 amino acid residues and the 5′ and 3′ UTRs of 7 and 1441 bp, respectively. Pm-p23 significantly matched p23-like protein of Nasonia vitripennis (E-value = 7 × 10− 46). The predicted molecular mass and pI of the deduced Pm-p23 protein was 19.07 kDa and 4.39, respectively. Quantitative real-time PCR analysis revealed that the expression levels of Pm-p23 in ovaries of both intact and eyestalk-ablated broodstock were significantly greater than that of juveniles (4-month-old shrimp) (P < 0.05). Pm-p23 was up-regulated since stage II ovaries of intact and stage III ovaries of eyestalk-ablated P. monodon broodstock (P < 0.05). The mRNA level of Pm-p23 after spawning was not significantly different from stages II–IV ovaries of intact broodstock (P > 0.05). In situ hybridization indicated that Pm-p23 was localized in ooplasm of previtellogenic oocytes. Recombinant Pm-p23 protein was successfully expressed in vitro and its polyclonal antibody was successfully produced. Western blot analysis indicated that the level of ovarian Pm-p23 protein peaked at the vitellogenic stage and decreased as oogenesis progressed. Taken together, results from this study strongly suggested functionally important roles of Pm-p23 gene products during vitellogenesis of P. monodon oocytes.