Characterization and expression analysis of the Broad-complex (Br-c) gene of the giant tiger shrimp Penaeus monodon

Broad-complex (Br-c) is the early ecdysone responsive gene encoding a family of zinc-finger transcription factors. In this study, the full-length cDNA of the Br-c gene of the giant tiger shrimp (Penaeus monodon) was identified. PmBr-c was 1897 bp in length containing an ORF of 1329 bp deducing to a polypeptide of 442 amino acids. PmBr-c was more abundantly expressed in ovaries than testes of P. monodon broodstock. The expression levels of PmBr-c mRNA in ovaries of juveniles was significantly greater than that in stages II (vitellogenic), IV (mature) and V (post-spawning) ovaries of intact broodstock. The expression level of PmBr-c was significantly increased in stage III (nearly mature) ovaries of intact wild broodstock and in stage IV ovaries of eyestalk-ablated broodstock (P < 0.05). In domesticated broodstock, ovarian PmBr-c was expressed lower in 18-month-old shrimp compared to 6-month-old shrimp (P < 0.05). In situ hybridization revealed that PmBr-c mRNA was localized in ooplasm of previtellogenic oocytes in various ovarian stages of P. monodon broodstock. Serotonin (5-HT, 50 μg/g body mass; 18-month-old shrimp) and progesterone (0.1 μg/g body mass; 14-month-old shrimp) injection significantly promoted the expression level of PmBr-c in ovaries of domesticated broodstock at 24 and 48-72 h post injection (hpi, P < 0.05). The expression levels of PmBr-c in ovaries of juvenile P. monodon was significantly increased following 20-hydroxyecdysone treatment (1 μg/g body mass; 4-month-old shrimp) for 168 hpi (P < 0.05). Taken together, PmBr-c seems to play an important role during ovarian development of P. monodon.