Identification of reproduction-related proteins and characterization of the protein disulfide isomerase A6 cDNA in ovaries of the giant tiger shrimp Penaeus monodon

Proteomic analysis was carried out for identification of proteins functionally involved in ovarian development of the giant tiger shrimp (Penaeus monodon). A total of 335 protein spots including 183 spots from vitellogenic (stage II) and 152 spots from mature (stage IV) ovaries of intact P. monodon broodstock were examined. Of these, 75 (40.98%) and 59 (38.82%) spots significantly matched known proteins in the databases, respectively. In addition, 270 protein spots including 167 and 103 spots from respective ovarian stages of eyestalk-ablated broodstock were also characterized. A total of 95 (56.89%) and 62 (60.19%) spots matched known proteins, respectively. Among differentially expressed reproduction-related proteins, the full-length cDNA of protein disulfide isomerase A6 (PmPDIA6) was further characterized by RACE-PCR. PmPDIA6 was 1946 bp in length containing an open reading frame (ORF) of 1293 bp corresponding to a polypeptide of 430 amino acids. PmPDIA6 was up-regulated at stage III ovaries in intact shrimp (P < 0.05). Interestingly, eyestalk ablation resulted in a lower expression level of PmPDIA6 in each stage of ovarian development compared to that of intact broodstock (P < 0.05). Results in this study clearly indicated the potential of cellular proteomic studies and gene expression analysis for identification of proteins/genes differentially expressed during ovarian development of P. monodon.