Effects of serotonin, progesterone and 17ß-estradiol on ovarian development of the black tiger shrimp Penaeus monodon

Abstract

Knowledge on molecular mechanisms of steroid hormones and neurotransmitters on expression of reproduction-related genes may lead to the possible ways to effectively induce ovarian maturation in shrimp. RT-PCR was carried out to examine the expression patterns of several genes. In addition, the full-length cDNAs of 17β–hydroxysteroid dehydrogenase (Pm17β–HSD) of the black tiger shrimp (Penaeus monodon) was isolated and it was 1400 bp in length containing an ORF of 768 bp corresponding to a polypeptide of 255 amino acids. In situ hybridization indicated that Pm17β–HSD mRNA was localized only in the cytoplasm of previtellogenic oocytes but not in more mature stages of oocytes. Recombinant Pm17β–HSD protein (26.78 kDa) was successfully expressed in the bacterial expression system. It was expressed at a very low level as the insoluble protein Quantitative real-time PCR was carried out to estimate the expression of reproduction-related genes in P. monodon. The expression levels of PmATP/GTP-BP and Pm17β-HSD were not differentially expressed during ovarian development in wild intact and eyestalk-ablated P. monodon. However, lower expression levels of these transcripts in stage II and III ovaries in eyestalk-ablated broodstock were found compared to those in intact broodstock (P < 0.05). The expression profiles of PmInx1 and PmPhb2 were similar as they were significantly increased in stages II-IV ovaries in intact broodstock (P < 0.05) and at stages III and IV ovaries in eyestalk-ablated broodstock (P < 0.05). Their expression levels in stages I, II, III and IV ovaries in eyestalk-ablated broodstock were greater than those in the same ovarian stages in intact broodstock (P < 0.05). In domesticated 5-, 9-, 14- and 19-month-old shrimp, the expression levels of PmATP/GTP-BP was not significantly different. In contrast, Pm17β-HSD in ovaries of 19 month-old shrimp was significantly greater than that in other groups of domesticated shrimp (P < 0.05). Injection of 17β-estradiol did not affect the expression level of PmATP/GTP-BP but resulted in a significant increase of Pm17β-HSD at 7 days after injection (P < 0.05). In contrast, progesterone injection resulted in a lower expression of both PmATP/GTP-BP and Pm17β-HSD in ovaries of 14-month-old shrimp at 72 hpi and 24-72 hpi, respectively (P < 0.05). Interestingly, serotonin injection promoted the expression level of PmATP/GTP-BP and Pm17β-HSD in ovaries of 18-month-old broodstock of P. monodon at 6-48 hpi (P < 0.05).