Identification and expression analysis of the Broad-Complex core protein isoform 6 (BR-C Z6) gene in the giant tiger shrimp Penaeus monodon (Penaeidae: Decapoda)

Abstract

Broad-Complex (BR-C) is an early ecdysone-responsive gene encoding a family of zinc-finger transcription factors that function during metamorphosis in insects. We identified two full-length cDNAs of BR-C Z6 in the giant tiger shrimp (Penaeus monodon). They were 2422 and 2060 bp in length, containing open reading frames of 1440 and 1443 bp, corresponding to polypeptides of 479 and 480 amino acids, respectively. Tissue distribution analysis indicated that PmBR-C Z6 was abundantly expressed in hemocytes and ovaries in juveniles. In broodstock, PmBR-C Z6 was constitutively expressed in all tissues examined, and the highest expression was observed in ovaries. The expression of PmBR-C Z6 in ovaries was significantly greater than in testes in both juveniles and broodstock of P. monodon. Quantitative real-time PCR indicated that the expression level of PmBR-C Z6 was significantly down-regulated in stages II and III of ovaries in intact wild broodstock and returned to the basal level in stage IV ovaries and after spawning. In eyestalk-ablated broodstock, PmBR-C Z6 was significantly up-regulated in stage IV (mature) ovaries. Moreover, the expression level of PmBR-C Z6 in vitellogenic, early cortical rod and mature (stages II-IV) ovaries of eyestalk-ablated broodstock was greater than that of the same ovarian stages in intact broodstock. In situ hybridization revealed that PmBR-C Z6 transcripts were localized in oogonia and cytoplasm of previtellogenic and vitellogenic oocytes of both wild intact and eyestalk-abated broodstock. The effects of 20-hydroxyecdysone on expression of PmBR-C Z6 were examined. The expression level of PmBR-C Z6 in ovaries of juvenile P. monodon was significantly increased at 168 h post-injection. Taken together, these findings indicate that PmBR-C Z6 plays an important role in ovarian development of P. monodon.