Nutrigenomics for increasing reproductive maturation of the black tiger shrimp penaeus monodon

Abstract

Isolation and expression analysis of reproduction-related genes is important for understanding molecular mechanisms of ovarian development in the giant tiger shrimp (Penaeus monodon). In this thesis, the partial cDNA sequences of nuclear hormone receptor (PmNHR96) and son of sevenless (PmSOS) were isolated. Their partial open reading frames (ORFs) were 879 and 1183bp, respectively. RT-PCR analysis revealed that asparagenyl tRNA systhetase (PmAtNS), aspartate amino transferase (PmAST) and PmSOS were more preferentially expressed in ovaries than testes of P. monodon. Quantitative real-time PCR indicated that the expression level of PmAtNS and Pm-mago nashi was not significantly different during ovarian development in both wild intact and eyestalk-ablated broodstock. The expression level of both PmAST and PmNHR96 was significantly increased in stage IV ovaries in intact P. monodon broodstock (P < 0.05). Eyestalk ablation resulted in significant greater expression levels of PmAST in stage II ovaries (P < 0.05), Pm-mago nashi in stages I-IV and PmNHR96 in stages I-III ovaries compared to those in intact broodstock (P < 0.05). Results suggested that these genes should play the important role during ovarian development of P. monodon. In domesticated shrimp, the expression level of PmAtNS was significantly decreased in 14-month-old shrimp (P < 0.05). In contrast, the expression level of PmNHR96 was significantly increased at 14 month-old shrimp (P < 0.05) and PmAST was significantly increased at 19-month-old shrimp (P < 0.05). Nevertheless, Pm-mago nashi was comparably expressed in different ages of domesticated shrimp. Exogenous injection of 17β-estradiol resulted in significantly reduction of ovarian PmAtNS at 7 days post injection but did not affect the expression level of PmAST and Pm-mago nashi. Nevertheless, the expression level of ovarian PmNHR96 seemed to be slightly increased at 7 days after injection (P > 0.05). Eyestalk ablation resulted in significant greater expression levels than that of the negative control for PmAST at 28 days post injection, for Pm-mago nashi at 7 days post injection and for PmNHR96 at 14 days post injection (P < 0.05) but did not affect the expression level of PmAtNS. The feeding trials for diet supplemented with 1 and 10 mg/kg 17β-estradiol was carried out for the duration of 35 days. The expression level of PmAtNS after feeding with the diet supplemented with 10 mg/kg of 17β-estradiol for 7 days was significantly lower than that of the control (P < 0.05). Similar results were also found for PmAST. Nevertheless, the treatment with 1 mg/kg of 17β-estradiol resulted in an increase expression level of PmAST after feeding for 35 days (P < 0.05). For Pm-mago nashi, its expression level was induced after feeding with the diet supplemented with 10 mg/kg of 17β-estradiol for 7 days. In contrast, feeding of diets supplemented with both 1 and 10 mg/kg of 17β-estradiol resulted in a lower expression level of Pm-mago nashi than that of the control at 14 days post treatment (P < 0.05). The expression levels of PmNHR96 were not significantly changed for both 1 and 10 mg/kg of 17β-estradiol (P < 0.05). Eyestalk ablation resulted in significant greater expression levels than negative control for PmAtSN, PmAST and PmNHR96 at 28, 35 and 14 days after treatment, respectively.