Abstract
The giant freshwater prawn, Macrobrachium rosenbergii, is an economically valuable species that are distributed throughout the Asia-Pacific region. With the natural population declining due to overfishing, aquaculture of this species is deemed necessary. Hence, it is essential to understand the mechanisms regulating reproduction in order to increase their production. Prostaglandins (PGs) play an important role in reproduction in most vertebrates and several invertebrates. It has been proposed that crustaceans have PGs but the prostanoids pathway in the giant freshwater prawn is still unclear. In this study, we identified 25 prostanoid-related genes involved in the biosynthesis of active prostanoids in M. rosenbergii using in silico searches of transcriptome data. Comparative analysis of encoded proteins for the MroPGES2 gene with other species was performed to confirm their evolutionary conservation. Gene expression analysis revealed the correlation of MroPGES2 gene expression level with the progress of ovarian development. Eyestalk ablation increased the expression level of MroPGES2 gene compared to intact groups during the ovary maturation stages. Collectively, this study confirmed the existence of prostanoids in the giant freshwater prawn, as well as characterizing key gene MroPGES2 associated with the prostanoid pathway. We propose that MroPGES2 may play an important role in M. rosenbergii ovarian maturation and its expression is under the inhibitory control from the eyestalk optic ganglion hormones. Identification of genes in prostanoid pathway and their expressions enables future functional studies to be performed, which may lead to applications in the aquaculture of this species.
Highlights
Macrobrachium rosenbergii, the giant freshwater prawn, has been highly valued as food in the tropical countries of Asia for domestic consumption and export (Hossain and Das, 2010; New and Nair, 2012)
Our present study has proven the existence of prostanoid pathway in the giant freshwater prawn, M. rosenbergii, as well as genes involved in the biosynthesis of active prostanoids
MroPGES2 and PGE2 expressions in ovaries were high during early stages of the ovarian cycle as well as in early oocytes, but subsided when the ovaries reached maturity and the oocytes became fully developed
Summary
Macrobrachium rosenbergii, the giant freshwater prawn, has been highly valued as food in the tropical countries of Asia for domestic consumption and export (Hossain and Das, 2010; New and Nair, 2012). The purposes of our studies are 1) to identity the complete set of enzymes involved in prostanoid biosynthesis pathway in the female M. rosenbergii through transcriptome analysis; 2) to characterize and investigate the tissue expressions of the key enzymes, namely, prostaglandin E synthase 2 (PGES2), representing the downstream or rate-limiting step enzyme in the production of PGE2 the major PG that is proven active in ovarian maturation (Sumpownon et al, 2015); and 3) to investigate whether the expressions of this enzyme is under the control of eyestalk optic ganglion hormones, especially gonad-inhibiting hormone (GIH) (Diwan, 2005; Nagaraju, 2011; Uawisetwathana et al, 2011). These studies will provide basic knowledge concerning the prostanoid biosynthesis pathway that controls the reproductive processes, the ovarian maturation in this decapod crustacean, which may be applied to the increase of prawn reproduction
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