Characterization and expression analysis of Cyclin-dependent kinase 7 gene and protein in ovaries of the giant tiger shrimp Penaeus monodon

• The full-length cDNA of Penaeus monodon Cdk7 (1407 bp) was characterized.
• PmCdk7 mRNA and protein were differentially expressed during ovarian development.
• The level of PmCdk7 mRNA in stages I–IV ovaries was induced by eyestalk ablation.
• 5-HT injection promoted its expression level in domesticated shrimp at 6–48 hpi.
• Nucleo-cytoplasmic translocation of PmCdk7 was observed during oocyte development.

The characterization of genes differentially expressed in ovaries is necessary for understanding the mechanisms involving ovarian developmental processes of the giant tiger shrimp (Penaeus monodon). Here, the full-length cDNA of P. monodon Cyclin-dependent kinase 7 (PmCdk7) was characterized. It was 1407 bp in length (ORF of 1062 bp corresponding to 353 amino acids). The expression of PmCdk7 in the ovaries was greater than that in the testes (P < 0.05). PmCdk7 was significantly up-regulated in stage IV (mature) ovaries in wild intact broodstock (P < 0.05). In wild eyestalk-ablated broodstock, its expression was earlier increased in stage III (late vitellogenic) ovaries (P < 0.05). The expression level of PmCdk7 during ovarian development (stages I–IV ovaries) in eyestalk-ablated broodstock was greater than that of the same ovarian stages in intact broodstock (P < 0.05). 5-HT (50 μg/g body weight) injection promoted its expression level in ovaries of domesticated 18-month-old shrimp at 6–48 h post injection (hpi). The rPmCdk7 protein and its polyclonal antibody were successfully produced. The positive immunoreactive band (67 kDa) was not observed in premature ovaries of juveniles. Western blot analysis revealed differential expression of PmCdc7 in stages II–IV ovaries compared with stage I ovaries in intact broodstock but it was comparably expressed among different ovarian developmental stages in eyestalk-ablated broodstock. Immunofluorescence revealed the positive signals of PmCdk7 in the ooplasm of previtellogenic oocytes and its subsequent nucleo-cytoplasmic translocation during oocyte development. Results indicated that PmCdk7 seems to play functional roles in the development and maturation of oocytes/ovaries in P. monodon.