Functions of Insulin-like Peptide Genes (CsILP1 and CsILP2) in Female Reproduction of the Predatory Ladybird Coccinella septempunctata (Coleoptera: Coccinellidae)

Insulin-like peptides (ILPs) are important peptide hormones in insects, particularly involved in regulating physiological processes such as growth, development, and reproduction. However, the specific roles of ILPs in the reproduction of natural enemy insects remain unknown. In this study, two ILP genes, <i>CsILP1</i> and <i>CsILP2</i>, were cloned and their functions were analyzed in female <i>Coccinella septempunctata</i> L. (Coleoptera: Coccinellidae). The open reading frames (ORFs) of <i>CsILP1</i> and <i>CsILP2</i> were 384 bp and 357 bp, respectively. The expression of <i>CsILP1</i> increased on the 6th day after eclosion, reaching its peak on the 12th day, while <i>CsILP2</i> levels showed a significant increase on the 6th day and then stabilized. In different tissues, <i>CsILP1</i> was highly expressed in ovaries, while <i>CsILP2</i> predominated in elytra. Injection of dsRNA targeting <i>CsILP1</i> and <i>CsILP2</i> resulted in the down-regulation of insulin pathway genes. The relative expression of ovarian development-related genes <i>Vasa</i>, <i>G2/M,</i> and <i>Vg</i> was reduced by 82.50%, 89.55%. and 96.98% in <i>dsCsILP1</i>-treated females, and by 42.55%, 91.36%, and 55.63% in <i>dsCsILP2</i>-treated females. Furthermore, substantial decreases in 14-day fecundity were observed, with reductions of 89.99% for <i>dsCsILP1</i> and 83.45% for <i>dsCsILP2</i>. These results confirm the regulatory functions of <i>CsILP1</i> and <i>CsILP2</i> in female <i>C. septempunctata</i> reproduction.