Identification of insulin-like peptide 1 (ILP1) gene and its expression in response to different food sources in the intertidal copepod Tigriopus japonicus

Abstract

Insulin-like peptide (ILP) is an important hormone that controls a wide array of functions including glucose or trehalose levels in body fluids in invertebrates. However, the presence and role of ILP in copepods is unclear. To better understand the functional role of ILP in marine copepods, we isolated insulin-like peptide 1 (Tj-ILP1) from the copepod Tigriopus japonicus, characterized its conserved motifs, and measured its transcriptional modulation in response to different food sources. The open reading frame of Tj-ILP1 cDNA was 525 bp in length, encoding 174 amino acid residues. Multiple alignments revealed that six conserved cysteine residues in the ILP peptide domain were conserved for maintaining a tertiary structure. The Tj-ILP gene showed high expression levels in adult males, suggesting an association with sexual differentiation and male morphogenesis in T. japonicus. Additionally, to examine the role of Tj-ILP in dietary metabolism, we provided two food supplies (Chlorella vulgaris and Tetraselmis suecica) to copepods and measured dose- and time-dependent expression of Tj-ILP1 mRNA in response to different carbohydrate sources. Tj-ILP1 transcription activity was significantly elevated in response to both algal food supplies, indicating that the Tj-ILP1 gene is inducible with different food sources.