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 (Penaeusmonodon). 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 molecularmass
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) (Pb0.05). Pm-p23was up-regulated since stage
II ovaries of intact and stage III ovaries of eyestalk-ablated P. monodon broodstock (Pb0.05). The mRNA level of
Pm-p23 after spawning was not significantly different from stages II–IV ovaries of intact broodstock (PN0.05). In
situ hybridization indicated that Pm-p23 was localized in ooplasm of previtellogenic oocytes. Recombinant Pmp23
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.
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