| Corcyra cephalonica is a common storage pest of Lepidoptera in tropical and subtropical regions,which seriously threatens food security.At present,insect attractants targeting the olfactory system of insects have been widely used in the control of pests,and have attracted more and more attention due to their high efficiency,specificity,non-toxicity and resistance to drug resistance.Attractant control mainly takes advantage of the specificity and sensitivity of insects to odor molecules.Therefore,it is necessary to deeply study the mechanism of insect olfactory perception and the structure and function of olfactory proteins involved in the recognition process.In this study,the C.cephalonica was taken as the research object,and the ultrastructure of its antennae was observed by scanning electron microscope,and the type,quantity and size of the olfactory receptors of the male and female C.cephalonica were compared.The odorant binding protein genes were comprehensively excavated and identified,and the tissue expression patterns of these genes were analyzed by qRT-PCR.In addition,homologous modeling method was used to construct the three-dimensional structure of C.cephalonica odorant binding protein,and the binding characteristics and ability of sex pheromone-binding protein and common odorant binding protein and sex pheromone were explored through molecular docking.It provides a new idea for the design and development of more efficient sex pheromone control technology of rice moth.The results are as follows:1.Observation of the ultrastructure of the antennal sensilla of the adult C.cephalonicaScanning electron microscope was used to observe the ultrastructure of the antennae of the female and male adult C.cephalonica.It was found that the antennae of the C.cephalonica were filamentous as a whole,and the average length of the antennae of the female moth(6.77±0.56 mm)was significantly longer than that of the male moth(5.23±0.42 mm).The antennal sensilla of male and female moths are mainly distributed on the ventral surface of the flag segment,and the sensilla types are the same,and there are 7 types,namely sensilla trichodea,sensilla chaetica,sensilla auricillica,sensilla squamiformia,sensilla styloconica,sensilla coeloconica and bohm-bristle,but males have significantly more sensilla than females.Among them,the sensilla trichodea is the most widely distributed and most numerous in both female and male moths,and the sensilla trichodeas in male moths(35.27 ± 3.42 μm)are significantly longer than those in female moths(28.27±2.87μm).The number of worms(24.87±2.26)was significantly more than that of females(20.43±2.65).In addition,the lengths of sensilla trichodea,sensilla squamiformia,sensilla coeloconica and bohm-bristle were significantly longer in males than in females,indicating that the ability of males to receive external chemical information may be significantly stronger than that of females.1.Identification of odorant-binding protein genes of C.cephalonica.On the basis of constructing the transcriptomes of the male and female of C.cephalonica,annotated in the NR,NT,KO,GO,KOG,PFAM and Swiss-Prot databases,a total of 25 odorant binding protein genes were identified through database annotation:20 odorant binding proteins(OBPs),2 general odorant binding proteins(GOBPs)and 3 sex pheromone binding proteins(PBPs),named respectively CcepOBP1-20,CcepPBP1-3 and CcepGOBP1,2.3.Cloning and tissue expression analysis of odorant-binding protein genesThe ORF of the C.cephalonica odorant binding protein was obtained by RT-PCR amplification.It is found that CcepOBP3,4,6,8,12,15,16 and PBP1,3 belong to classical acids;CcepOBP7,9,13,20 belong to plus-C-A type;CcepOBP10,11,14,CcepGOBP1,2 and CcepPBP2 belong to plus-C-B type;CcepOBP1,2,5,18 belong to Minus-C type;CcepOBP17,19 belong to Atypial.The expression of the above 25 genes in different tissues(antennae,head,thorax,abdomen,feet and wings)of male and female adults was analyzed by qRT-PCR.The results showed that CcepPBPs and CcepGOBPs were specifically expressed on the antennae.The expression of CcepPBPs was significantly higher in male than in female tentacles,and the expression in male moth tentacles was about 1.9,4.5 and 1.4 times higher than that in female tentacles,respectively.In contrast,the expression levels in the antennae of female moths were about 3.5 and 3.6 times higher than those in the antennae of male moths,respectively.CcepOBPs were mainly expressed in the head(without antennae)and antennae,followed by a small amount in the wings.4.Homology modeling and molecular docking of CcepOBPsThe three-dimensional structures of CcepOBP1,5,12,18,CcepPBP1-3 and CcepGOBP1,2 were successfully constructed by homology modeling.The two reported sex pheromones of C.cephalonica were selected for molecular docking with CcepPBP1-3 and CcepGOBP1,2,and found that CcepPBP1-3,GOBP1,2 and 3,7,11-trimethyl-2,6,10-dodecane.The binding energy of carbatrienal is concentrated in-6.6～-3.5 kJ/mol;the binding energy with 6,10,14-trimethyl-2-pentadecanol is distributed in-4.4～-1.58 kJ/mol.Both CcepPBPs and CcepGOBPs have better binding ability to 3,7,11-trimethyl-2,6,10-dodecatrienal.In terms of binding characteristics,the key forces of CcepPBP1,3 and the two sex pheromones are hydrogen bonds,and the key binding sites are SER160,MET29,ASP173,and GLN30,respectively.The key interaction between CcepPBP2 and 3,7,11-trimethyl-2,6,10-dodecatrienal is hydrophobic interaction,and the binding site is ALA 13 6;with 6,10,14-trimethyl-2-Pentadecanol has no critical force.The key binding forces between CcepGOBP1 and 2 and the two sex pheromones are hydrogen bonds,and the key binding sites are ILE117. |
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