RNAi Reveals Role of Insulin-Like Androgenic Gland Hormone 2 (IAG2) in Sexual Differentiation and Growth in Hermaphrodite Shrimp

Abstract

Insulin-like androgenic gland hormone (IAG) is the most widely known hormone that regulates sexual differentiation in crustaceans. Previously, a transcriptome study described two transcripts of IAGs ( Lvit-IAG1 and Lvit-IAG2 ) in the peppermint shrimp Lysmata vittata , a species characterized by a rare reproductive system of protandric simultaneous hermaphroditism (PSH). Herein, we explored the function of Lvit -IAG2 via RNA interference (RNAi) experiments, and then compared the functional differences between the two IAGs. We demonstrated that Lvit -IAG2 positively regulated the expression of crustacean hyperglycemic hormone ( Lvit-CHH ) in eyestalk ganglion but exhibited no significant effect on the expression of gonad-inhibiting hormone ( Lvit-GIHs ) and crustacean female sex hormone ( Lvit-CFSHs ). Besides, Lvit-IAG2 gene knockdown caused degeneration in appendices masculinae (AM) and suppressed germ cells at the secondary spermatocyte stage. Moreover, silencing the Lvit-IAG2 gene impeded ovarian development, including smaller previtellogenic oocytes, and lower expression of vitellogenin ( Lvit-Vg ) gene in hepatopancreas and vitellogenin receptor ( Lvit-VgR ) gene in the ovarian region. Notably, silencing the Lvit-IAG2 gene impeded individual growth of the species. Collectively, findings from this study demonstrate that Lvit -IAG2 and Lvit -IAG1 coordinatively function to modulate sexual differentiation in L. vittata ; meanwhile, Lvit -IAG2 stimulates the growth of the PSH species.