Serotonin induced changes in the expression of ovarian gene network in the Indian white shrimp, Penaeus indicus

The potential effect of serotonin (5-hydroxytryptamine, 5-HT) to induce oocyte maturation in the white shrimp, Penaeus indicus was examined in the present study. Serotonin treatment was given to intact and unilaterally eyestalk ablated females at 50μg/g body weight and the differential expression of ovarian genes involved in vitellogenesis [vitellogenin (vg), vitellogenin receptor (vgr)] and meiotic maturation [cyclin-dependent kinase 2 (cdc2), cyclin B and thrombospondin (tsp)] was examined. Quantitative real-time PCR indicated that the levels of vg, cdc2 and cyclin B increased with advancement in ovarian maturation. Significant increase in the expression of these genes in the eyestalk ablated (ESA) and 5HT+ESA group indicated post-vitellogenic meiotic resumption and maturation of oocytes. It was also observed that for effective stimulation of ovarian maturation by serotonin, the levels of inhibitory hormone should be removed. The significant increase in cdc2 and cyclin B levels in 5HT+ESA compared to ESA suggests that serotonin acts synergistically with other stimulatory hormones during eyestalk ablation to stimulate ovarian maturation. The present investigation suggests a possible dual regulatory role of serotonin on both vitellogenesis and indirect stimulation of post-vitellogenic meiotic resumption and oocyte maturation in penaeid shrimps.Ovarian maturation and associated changes in the expression profile of ovarian genes in intact and unilaterally eyestalk ablated females treated with serotonin confirms the regulatory role of serotonin on ovarian maturation in Penaeus indicus. Significant increases in the expression of genes were observed in ablated females treated with serotonin. The possible dual regulatory role of serotonin on both vitellogenesis and indirect stimulation of oocyte maturation in penaeid shrimps is suggested.