Abstract
The soluble carrier proteins, OBPs carry odor components through sensilium lymph to specific receptors within the antennal sensilla to trigger behavioral responses. Herein, McinOBP4 was characterized from the Macrocentrus cingulum, which is the specialist parasitic insect of Ostrinia furnacalis for better understanding of olfactory recognition mechanism of this wasp. The classical odorant binding protein McinOBP4 showed good binding affinity to corn green leaf volatiles. RT-qPCR results showed that the McinOBP4 was primarily expressed in male and female wasp antennae, with transcripts levels differing by sex. Fluorescence assays indicate that, McinOBP4 binds corn green leaf volatiles including terpenoides and aliphatic alcohols as well as aldehydes with good affinity. We have also conducted series of binding assay with first mutant (M1), which lacked the last 8 residues and a second mutant (M2), with Met119 replaced by Leucine (Leu119). In the acidic conditions, affinity N-phenylnaphthylamine (1-NPN) to McinOBP4 and M1 were substantially decreased, but increase in basic condition with no significant differences. The lack of C-terminus showed reduced affinity to terpenoides and aliphatic alcohols as well as aldehydes compounds of corn odorants. The mutant M2 with Met119 showed significant reduction in binding affinity to tested odorants, it indicating that Met119 forming hydrophobic chain with the odorants functional group to binding. This finding provides detailed insight of chemosensory function of McinOBP4 in M. cingulum and help to develop low release agents that attract of this wasp to improve ecologically-friendly pest management strategy.
Highlights
The sense of smell is important for insects to detect chemicals cues in their surrounding environment and controlling fundamental behaviors as foraging, host-seeking, mating choice, oviposition site locating by females, warning, and defense as well as avoiding threats
McinOBP4 was identified in the antennal transcriptomic analysis, is a protein highly expressed in olfactory tissues expressed in antennae
McinOBP4 was phylogenetically closest to MmedPBP1 from other tissues, might be the McinOBP4 was expressed in adult antennae (Figure 2)
Summary
The sense of smell is important for insects to detect chemicals cues in their surrounding environment and controlling fundamental behaviors as foraging, host-seeking, mating choice, oviposition site locating by females, warning, and defense as well as avoiding threats. C-terminus Methionene, Involvement in Odorant Binding strategies which could be alternative to chemical based controlling Membrane proteins such as odorant receptor (ORs), ionotropic receptors (IRs), and sensory neuron membrane proteins (SNMPs) play central roles in translating the chemo signals to an electrical signal, while odorant binding proteins (OBPs), or chemosensory proteins (CSPs) are proposed to bound, convey, and even recognize exact pheromones and odorants to their specific receptors (Jacquin-Joly and Merlin, 2004; Leal, 2013; Sun et al, 2016). The C-terminus in ApolPBP1, forming the seventh α -helix, played crucial role in odorant binding and/or locking the odor molecules in the binding cavity as well (Katre et al, 2013) Previous studies reported this type of conformational changed in several OBPs (Damberger et al, 2007; Sun et al, 2013). OBPs were suggested to probably exhibit different ligand binding and releasing mechanisms
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