RNAi of Neuropeptide CCHamide-1 and Its Receptor Indicates Role in Feeding Behavior in the Pea Aphid, Acyrthosiphon pisum

Neuropeptide <i>CCHamide-1</i> (abbreviated as <i>CCHa1</i>) is a recently discovered peptide that is present in many arthropods and is the ligand of the <i>CCHa1R</i>, a member of the G protein-coupled receptors (GPCRs) superfamily, which plays a regulatory role in diverse physiological processes such as feeding, circadian rhythm, insulin production, lipid metabolism, growth, and reproduction. However, the function of this gene in aphids is still unknown. Here, we characterized and determined the potential role of <i>CCHa1</i>/<i>CCHa1R</i> signaling in the pea aphid, <i>Acyrthosiphon pisum</i>, which is a notorious pest in agriculture. The docking analysis revealed that the <i>CCHa1</i> peptide binds to its receptor <i>CCHa1R</i> through specific amino acid residues, which are critical for maintaining the structural and functional integrity of the peptide-receptor complex. Quantitative real-time reverse transcription-PCR (qRT-PCR) revealed the expression levels of <i>CCHa1</i>/<i>CCHa1R</i> transcripts in different development stages and different tissues, indicating that the <i>CCHa1</i> expression was high in the first nymphal instar compared to the upcoming nymphal instars and adults, and was predominantly high in the brain. The <i>CCHa1</i>/<i>CCHa1R</i> transcript levels were significantly upregulated in starved aphids compared to fed aphids. Moreover, RNAi knockdown by the injection of dsRNA-<i>CCHa1</i> and dsRNA-<i>CCHa1R</i> significantly reduced the corresponding expression of the target gene and reduced their food intake in adult aphids, as revealed by the electrical penetration graph results. <i>CCHa1</i>/<i>CCHa1R</i>-silencing also reduced the reproduction, but not the survival, in <i>A. pisum</i>. Our data demonstrated that <i>CCHa1/CCHa1R</i> play a role in the regulation of feeding in <i>A. pisum</i>, suggesting a role of the <i>CCHa1</i> signaling pathway in the aphids relating to their nutritional status.