Molecular characterisation and developmental expression analysis of the 5-HT7 receptor in Chrysopa formosa

Serotonin (5-hydroxytryptamine, 5-HT) is a key monoamine neurotransmitter in insects, which regulates neural functions and influences various developmental and physiological processes by binding to its receptors. In this study, we investigate the molecular characteristics, phylogenetic relationships, and expression patterns of the 5-HT7 receptor (Cf5-HT7) in Chrysopa formosa, with a focus on its potential involvement in developmental and diapause regulation. The Cf5-HT7 gene was identified and cloned from the C. formosa transcriptome, revealing an open reading frame of 1788 bp encoding a 596 amino acid protein. Sequence analysis confirmed that Cf5-HT7 is a typical class A G protein-coupled receptor, characterised by seven transmembrane domains and several post-translational modifications, including palmitoylation and N-glycosylation sites. Phylogenetic analysis revealed that Cf5-HT7 is most closely related to the 5-HT7 receptor from Chrysoperla carnea, with high conservation of key motifs involved in ligand binding and receptor activation. Expression analysis across different developmental stages of C. formosa showed that Cf5-HT7 is highly expressed in the first instar larvae, with significant upregulation observed during the prepupal stage. Under diapause-inducing conditions, Cf5-HT7 expression is modulated in a stage-specific manner, showing a marked decrease at the onset of diapause, followed by a significant increase during the mid-to-late diapause maintenance phase. These findings suggest that it plays a pivotal role in regulating development and diapause processes in C. formosa, offering new insights into the molecular mechanisms governing insect life cycle transitions. This study lays the groundwork for future research into the functional roles of 5-HT7 receptors in insect physiology and their potential applications in manipulating diapause.