Insulin-like Peptide Receptor (ILPR) in the Cuttlefish Sepiella japonica: Characterization, Expression, and Regulation of Reproduction

Insulin-like peptide receptor (ILPR) can effectively regulate ovarian development in invertebrates, but its effect in cuttlefish has not been reported. We isolated and characterized a ILPR gene from Sepiella japonica, referred to as SjILPR. This gene displayed significant homologies to Octopus bimaculoides ILPR, and contained all typical features of insulin receptors and tyrosine kinase domain structure. SjILPR is expressed in all detected tissues, with the highest expression in the ovary. During ovarian development stages, its expression levels in the ovary, pancreas, and liver were correlated to the female reproductive cycle. After the silencing of SjILPR in vivo, comparative transcriptome analysis identified 4314 differentially expressed genes (DEGs) in the injected group, including 2586 down-regulated genes and 1728 up-regulated genes. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses revealed that 832 DEGs were assigned to 222 pathways, many pathways of which were related to gonadal development. Four down-regulated genes relevant to ovarian development (Vitellogenin 1, Vitellogenin 2, Cathepsin L1-like, and Follistatin) were selected to confirm the accuracy of RNA-seq data by qRT-PCR. These results showed that SjILPR might regulate ovarian development to control reproduction by affecting the expression of the relevant genes in female S. japonica.