Abstract
Androgenic glands (AGs) are unique endocrine glands regulating male sexual differentiation and possibly growth in male crustaceans. In the prawn Macrobrachium rosenbergii sex reversal was achieved by AG grafting or removal into females and out of males, respectively. AGs in the prawn M. rosenbergii were hypertrophied through an endocrine manipulation and served in the construction of an AG cDNA subtractive library. Screening of this library revealed an AG specifically expressed gene, termed M. rosenbergii insulin-like AG factor (Mr IAG). This gene's cDNA was cloned and fully sequenced. The predicted mature peptide of Mr-IAG (B and A chains) showed high similarity in its cysteine backbone but low sequence homology to other crustacean AG specific insulin-like peptides. In vivo, Mr-IAG dsRNA injections to young males temporally prevented the regeneration of male secondary sexual features accompanied by a delay in molt and growth parameters. Moreover, prominent histological changes were observed following Mr-IAG silencing; arrest of spermatogenesis in the testis, absence of spermatozoa in the sperm duct and hypertrophied and hyperplasic AGs. This is the first instance in which silencing of an AG specifically expressed gene affects male sexual characteristics. Based on the above, Mr-IAG predicted protein is suggested as an AG hormone mediating male sex characteristics and maintenance of the male phenotype.