Captive maturation studies in Penaeus monodon by GIH silencing using constitutively expressed long hairpin RNA

Abstract

Captive maturation and spawning in Penaeus monodon are currently induced by unilateral eyestalk ablation, a method that removes the gonad-inhibiting hormone (GIH) secreted from the eyestalk. However, unilateral eyestalk ablation creates physiological complications in the brooder due to the unintended removal of other hormones secreted by the eyestalks. Here we studied the effect of gih silencing by long hairpin RNA on the reproductive physiology of P. monodon. We observed 3–5 fold enhanced expression of the androgenic gland hormone (AGH) transcript in males, but no effect on vitellogenin expression in females. In the destalked animals, however, positive effect on the maturation indicator transcripts was seen in both the sexes, and surpassed the efficiency of the silencing treatment. There were indications of active spermatogenesis in histological sections of both the gih silenced and destalked males, but no changes at histological level in the females. We also observed a significantly higher rate of molting and associated mortality in the gih silenced animals at the end of the experiment. Our results suggest that eyestalk ablation is still the most efficient technique to induce maturation in P. monodon. Although gih silencing could be a potential alternative to eyestalk ablation, further research is needed to enhance its efficiency over eyestalk ablation by using tissue specific and/or inducible promoter for lhRNA expression. It is also evident that females need to be fairly large in size for these interventions to succeed. Statement of relevanceInduction of captive maturation has been a challenge for shrimp industry. The seed production is often hampered by the low abundance and high price of naturally collected broodstock. Collection of natural brooders also has the intrinsic problem of WSSV infection. Also, genetic improvement of this highly preferred species is difficult unless the reproductive cycle is closed. For all these reasons it is important to study the reproductive physiology and endocrinology of this species and ways to manipulate it in order to induce captive maturation. The present study utilizes the RNA interference mechanism to silence the gonad-inhibiting hormone gene to see its effect on maturation.