Molecular Characterization and Key Binding Sites of Sex Pheromone-Binding Proteins from the Meadow Moth, Loxostege sticticalis

Abstract

The meadow moth, Loxostege sticticalis, is a typical agricultural pest that uses sex pheromones to mediate mating behavior; however, the mechanism underlying the selectivity of its pheromone-binding proteins (PBPs) remains unknown. In this study, LstiPBP1 and LstiPBP3 were cloned, expressed, and purified, and the fluorescence binding assay showed that LstiPBP1 binds to the major sex pheromone component, E-11-tetradecenol (E11-14:OH), with high affinity; moreover, E11-14:OH could evoke a significant antennal electrophysiological response and attract L. sticticalis males. After LstiPBP1 was silenced, both the antennal response and attractiveness of E11-14:OH decreased significantly. Molecular docking predicted that a hydrogen bonding site, Leu37, played key role in the binding of LstiPBP1 to E11-14:OH. After Leu37 was mutated, the E11-14:OH-binding affinity decreased drastically. These results suggest that LstiPBP1 participates in E11-14:OH recognition and could be used as a target gene to disturb the mating behavior of L. sticticalis and develop new odorants for pest control.

Ligand‐binding properties of odorant‐binding protein 6 in Athetis lepigone to sex pheromones and maize volatiles

“…Our results revealed that M39A, V68A, W106A, Q107A, and Y114A mutant proteins lost their ability to bind the ligands, suggesting that these residues may be involved in the binding affinity of AlepOBP6 to distinct ligands (key residues of Z 7‐12:Ac: W106 and Y114; Z 9‐14:Ac: V68, W106, and Y114; n ‐nonane and 1‐octen‐3‐ol: M39; (−)‐limonene, n‐nonane, benzaldehyde, decanal, 1‐octen‐3‐ol: Q107; Z 9‐14:Ac, α‐pinene, myrcene, 2‐hexanone, 2‐heptanone, 6‐methyl‐5‐hepten‐2‐one: V68 and Y114). Some studies have confirmed that the mutation of putatively crucial residues to alanine leads to a loss or decrease in the binding ability of OBPs to sex pheromones and host volatiles in other insects, 52,60,61,63–65 and this corresponds with our results. However, we also found no significant difference in the binding affinity of three ligands, (−)‐limonene, benzaldehyde and decanal, between M39A mutant and wild‐type AlepOBP6, which may be due to the bioinformatics prediction not being able to fully simulate the complex internal environment of insects.…”

“…Many studies have shown that insect OBPs usually bind distinct ligands with nonpolar and polar amino acid residues in a hydrophobic cavity 37,43,52,60–62 . Based on analysis of the binding models of AlepOBP6 to all 12 ligands, we also found that there were key nonpolar and polar residues involved in AlepOBP6 binding, suggesting that its ligand binding mechanism is consistent with that of insect OBPs 40–44 .…”

“…This is similar to the homologous OBP gene AlinOBP4 which is highly expressed in the adult male antennae of hemipteran mirid bugs, suggesting that ABPX may have a conservative role in enhancing sexual communication and host recognition in Lepidoptera and Hemiptera 20 . It is worth noting that the binding of sex pheromones and host plant volatiles is also a characteristic of PBPs in several moths, particularly noctuid insects 21,22,52,59 . Recently, we reported the function of AlepPBP1 in A. lepigone , 21 and there are some similarities and differences between AlepPBP1 and AlepOBP6 in their ligand binding characteristics: (i) both were highly expressed in male antennae and had a certain binding affinity to sex pheromones and maize volatiles; (ii) AlepPBP1 had the highest binding affinity to sex pheromones, while AlepOBP6 did not; and (iii) AlepOBP6 (12 ligands) had a wider binding spectrum than AlepPBP1 (eight ligands), and seven ligands were similar between the two.…”

“…These analyses suggest that the ligand‐binding mechanisms of AlepOBP6 and CcapOBP22 may be similar, and CcapOBP22 could be used as a reliable model in subsequent analyses. The binding energy between AlepOBP6 and each ligand was then calculated (Table 1), and the results showed that all docking binding energies were negative and the distances of all potential interaction residues were less than 4 Å (Figure 5), indicating that there is a strong interaction between AlepOBP6 and the 12 different ligands, similar to other insect OBPs 37,43,52 …”

Latest Developments in Insect Sex Pheromone Research and Its Application in Agricultural Pest Management

“…Oliveira et al [ 101 ] has reported the use of RNAi technique to identify the PBP RproOBP27, involved in sex pheromone detection of Rhodnius prolixus. Identification and molecular characterization of PBPs from multiple insect species, such as Cydia pomonella [ 100 ], Chilo suppressalis [ 102 ], Loxostege sticticalis [ 103 ], and Conogethes pinicolalis [ 104 ] have been reported in recent years. PBP1 from S. exigua [ 105 ] and Cyrtotrachelus buqueti [ 106 ] can also bind to plant volatile compounds, such as benzaldehyde, linalool, indole, and other carboxylic acids, in addition to pheromone molecules.…”