Identification and characterization of a sex peptide receptor-like transcript from the western tarnished plant bug Lygus hesperus.

Lygus hesperus females exhibit a post-mating behavioural switch that triggers increased egg laying and decreased sexual interest. In Drosophila melanogaster, these changes are controlled by sex peptide (SP) and the sex peptide receptor (DmSPR). In Helicoverpa armigera, SPR (HaSPR) also regulates some post-mating behaviour; however, myoinhibiting peptides (MIPs) have been identified as the SPR ancestral ligand, indicating that SPR is a pleiotropic receptor. In the present study, we identified a transcript, designated L. hesperus SPR (LhSPR), that is homologous to known SPRs and which is expressed throughout development and in most adult tissues. LhSPR was most abundant in female seminal depositories and heads as well as the hindgut/midgut of both sexes. In vitro analyses revealed that fluorescent chimeras of LhSPR, DmSPR and HaSPR localized to the cell surface of cultured insect cells, but only DmSPR and HaSPR bound carboxytetramethylrhodamine-labelled analogues of DmSP21-36 and DmMIP4. Injected DmSP21-36 also failed to have an effect on L. hesperus mating receptivity. Potential divergence in the LhSPR binding pocket may be linked to receptor-ligand co-evolution as 9 of 13 MIPs encoded by a putative L. hesperus MIP precursor exhibit an atypical W-X7 -Wamide motif vs the W-X6 -Wamide and W-X8 -Wamide motifs of Drosophila MIPs and SP.