First identification of an insulin-like androgenic gland (IAG) homolog and putative IAG-switch related genes in Macrobrachium amazonicum (Heller, 1862)

Abstract The androgenic gland (AG) is a male-specific endocrine organ in crustaceans, playing a crucial role in sexual differentiation. The function of the AG in decapods has been attributed to the expression of the insulin-like androgenic gland hormone ( IAG ) encoding gene which in Macrobrachium rosenbergii was shown to serve as a sexual switch (IAG-switch) for natural sexual differentiation as well as for sex manipulations. Macrobrachium amazonicum is a native South American species that has gained interest in recent years for aquaculture biotechnologies. However, the IAG gene of this species has not yet been identified, which limits further studies on its applications. In the present study, we constructed transcriptomic libraries of M. amazonicum male reproductive system (MRS), hepatopancreas (HE), and muscle (MU). Using the MRS libraries, we performed in silico search, identification, and characterization of an IAG gene homolog. The complete IAG open reading frame was identified in all M. amazonicum MRS cDNA libraries. Ma-IAG contains typical regions of the insulin-like growth factor gene superfamily. RT-PCR analyses confirmed Ma-IAG expression exclusively in the AGs. The differentiation into and deviation between maleness and femaleness are complex multigenic processes. Following the identification of Ma-IAG , we conducted a comprehensive search for putative genes related to the IAG-switch in the transcriptomic libraries of M. amazonicum , aiming to encompass genes potentially involved in these processes. Indeed, several upstream and downstream genes putatively associated with IAG were identified, including SoxE , Transformer-2 , Masc , and Dmrt family members. This study represents the first step toward a broader understanding of the IAG regulatory axis in M. amazonicum , its possible manipulations and development of biotechnological tools applicable to the aquaculture of this species.