A novel unique terminal ampullae-expressed insulin-like peptide in male white shrimp, Penaeus vannamei

Abstract

In crustaceans, sex differentiation is primarily regulated by insulin-like peptide which is expressed in male-specific androgenic gland. And, the insulin signaling pathway is crucial in gonad development and reproduction. However, the information of sexual regulatory genes, involved in sex differentiation of Penaeidea, is still fragmented. In the present study, a novel insulin-like peptide, termed Pv-ILP, was identified from the white shrimp Penaeus vannamei and the effect of Pv-ILP knockdown on sex differentiation was explored. Firstly, the predicted Pv-ILP protein consists of a signal peptide, B chain, C peptide, and A chain in order, and it has a similar structural organization as identified crustacean insulin-like androgenic gland hormones (IAGs). Secondly, Pv-ILP had a closer relative to P. vannamei and Penaeus mondon IAG and was subgrouped with Penaeidea by phylogenetic tree analysis. The multiple sequence alignment results indicated that Pv-ILP showed relatively high sequence similarity with other Penaeidae. Meanwhile, Pv-ILP was exclusively expressed in the terminal ampullae and gradually increased with individual development. On the other hand, Pv-ILP knockdown in undifferentiated postlarvae did not achieve sex reversal, which was different from that of IAGs in prawns. Significantly, one up-regulated nuclear receptor, two down-regulated transcripts, vitellogenin receptor, and guanylate cyclase, were focused as differentially expressed unigenes after Pv-ILP knockdown. These data provide a more theoretical basis for elucidating the sex differentiation mechanism of crustaceans.