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Submitted to: Insect Molecular Biology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 12/17/2013 Publication Date: 1/27/2014 Publication URL: http://handle.nal.usda.gov/10113/58784 Citation: Hull, J.J., Brent, C.S. 2014. Identification and characterization of a sex peptide receptor-like transcript from the western tarnished plant bug, Lygus hesperus. Insect Molecular Biology. 23:301-319. Interpretive Summary: After mating, Lygus hesperus females increase egg laying and show little receptivity to renewed mating. Virgin females, in contrast, lay few eggs and are receptive to mating. In some insects, this change in female behavior has been attributed to interactions between a chemical messenger (sex peptide), which is transferred by males to females during mating, and its receptor, the sex peptide receptor (SPR). This interaction can be thought of in terms of a “lock” (the receptor) and a “key” (the peptide). Because the SPR lock is present in a numerous insects, we hypothesized that a similar lock-and-key mechanism drives Lygus mating as well. In this study, we identified the L. hesperus SPR (termed LhSPR) and showed that it is similar to other SPRs in structure and in its location within the cell. Unexpectedly, peptide keys that have been shown to interact with other SPRs were unable to interact with LhSPR. We speculate that the reason for the lack of interaction is the nature of the peptide keys in Lygus, which would result in a differently shaped LhSPR lock from that of the other locks. A search for potential peptide keys revealed that one such set of keys does indeed have a different shape. Better understanding of how this insect uses and responds to these types of peptide keys may lead to new pest controls that interfere with Lygus reproduction or other essential biological processes. Technical Abstract: Lygus hesperus females exhibit a post-mating behavioral switch that triggers increased egg laying and decreased sexual interest. In Drosophila melanogaster, post-mating changes in behavior are controlled by sex peptide (SP) and the sex peptide receptor (DmSPR). SPR is present in most insect genomes, but ligand specificity varies with myoinhibiting peptides (MIPs) identified as the ancestral ligand. Post-mating changes in Helicoverpa armigera that are mediated by SPR (HaSPR) suggest a pleiotropic receptor with some functional conservation. In this study, we identified a transcript, designated L. hesperus SPR (LhSPR), homologous to known SPRs that is expressed throughout development and most adult tissues. Relative qPCR indicated higher LhSPR abundance in female seminal depositories and heads as well as the hindgut/midgut of both sexes. Fluorescent chimeras of LhSPR, DmSPR, and HaSPR all localized to the cell surface of cultured insect cells but only DmSPR and HaSPR bound carboxytetramethylrhodamine-labeled analogs of previously characterized SPR ligands. Furthermore, injected DmSP21-36 had no effect on L. hesperus receptivity. Potential divergence in the LhSPR ligand-binding pocket may be linked to receptor-ligand co-evolution. A putative L. hesperus MIP precursor encodes multiple MIPs exhibiting a W-X7-W motif as opposed to the W-X6-W and W-X8-W motifs of most MIPs and SP. |
