The characterization and knockdown of a male gonad-specific insulin-like receptor gene in the white shrimp Penaeus vannamei

The insulin-like androgenic gland-specific peptide is a known primary regulator of sexual differentiation in crustaceans. However, the knowledge of the crucial elements involved in the insulin-like signaling cascade remains fragmented. Here, we characterized a novel insulin-like receptor gene in the white shrimp Penaeus vannamei and named as Pv-IR. The deduced amino acid sequence of Pv-IR contained conserved domains of IRs, including two ligand-binding domains, a furin-like domain, three fibronectin-3 domains, and an intracellular tyrosine kinase domain in order. Multiple sequence alignment of the first ligand-binding domain and the tyrosine kinase domain in Pv-IR revealed a high degree of similarity in all representative IRs. The phylogenetic analysis presented that Pv-IR was clustered into a separate branch with IRs from decapods. The tissue distribution analysis showed that Pv-IR was predominantly expressed in the sperm duct and terminal ampullae of the male reproductive system in P. vannamei. Meanwhile, Pv-IR knockdown was carried out in postlarvae. Although the sex reversal phenotype was not observed, the effects of Pv-IR silencing on the expressions of related-genes were analyzed by the comparative transcriptomic sequencing. Significantly, two down-regulated transcripts (clottable protein and insulin-like peptide) and two up-regulated transcripts (flotillin and thyroid stimulating hormone receptor) were focused as gonad-related differentially expressed unigenes in Pv-IR knockdown. The data provided a more theoretical basis for elucidating the mechanism of sexual differentiation in crustaceans.