| The Asian corn borer,Ostrinia furnacalis,is the main pest of corn in China,which seriously affects the yield and quality of corn.Current management practices for this insect pest mainly rely on sprays of insecticides,however,the extensive use of chemical pesticides would pollute the environment,kill natural enemies,and cause insecticide resistance.Therefore,it is urgently to develop novel environmentally friendly strategies for pest management.One of the important research direction is to study the molecular mechanism of insect olfactory and regulate the olfactory-mediated behavior.For example,silence of key genes involved in the olfactory process can effectively block the communication between insects and their mates and hosts.The odorant recognition process of insects is quite complicated.Previous studies demonstrated that various kinds of proteins are involved in the process,including odorant-binding proteins(OBPs),chemosensory proteins(CSPs),odorant receptors(ORs),ionotropic receptors(IRs),sensory neuron membrane proteins(SNMPs)and odorant-degrading enzymes(ODEs).However,numerous studies mainly focus on OBPs,CSPs,ORs,IRs and SNMPs,the researches on ODEs are still limited.ODEs play an important role in the olfactory process in insects.After activation of odorant receptors,stray odorant molecules need to be rapidly removed by ODEs to avoid receptor saturation and allow OSNs to respond to the new stimuli.Therefore,inhibition of the activity of ODE enzymes,and knockout or knockdown of ODE genes,would significantly affect the olfactory and behavioral responses of insects to their host and mates,achieving the purpose of pest control.This paper focus on the identification and characterization of ODEs in O.furnacalis.The results will lay a theoretical foundation not only for the understanding of odorant degradation mechanism in olfactory process in O.furnacalis,but also for the development of ODE-based control techniques for this pest species.The findings of this paper are listed as follows: 1.Antennal transcriptome sequencing and ODE identification in O.furnacalisTranscriptome sequencing was performed on the antennae of O.furnacalis.The original reads were assembled to 35,056 unigenes.Of these,21,012 unigenes(59.94% of the total unigenes)were annotated by searching against the NCBI non-redundant database.Functional classification of these unigenes were also conducted by using three databases Gene Ontology(GO),Eukaryotic Orthologous Groups(KOG),and Kyoto Encyclopedia of Genes and Genomes(KEGG).By using bioinformatic methods,a total of 79 genes related to odorant degradation were identified from the antennal transcriptome,including 19 carboxylesterases(CXEs),17 glutathione S-transferases(GSTs),24 cytochrome P450(CYPs),13 UDP-glycosyltransferases(UGTs),and 6 aldehyde oxidases(AOXs).2.Expression profile analysis of ODE genes in O.furnacalisThe expression patterns of 19 CXEs and 1 GST(OfurGSTd1)in various adult tissues of O.furnacalis were analyzed by using real-time quantitative PCR.The results showed that,seven genes(OfurCXE2/5/7/10/14/15/18)were predominantly or highly expressed in the antennae.Of these,OfurCXE2,OfurCXE5 and OfurCXE18 were enriched in male antennae,while OfurCXE7,OfurCXE10 and OfurCXE15 were enriched in female antennae.OfurCXE14 was expressed at near-equal amounts in male and female antennae.In addition,OfurGSTd1 was specifically expressed in the antennae of both sexes,indicated that the protein encoded by the gene may involved in the degradation of odorants.3.Prokaryotic expression and activity assay of the OfurGSTd1 from O.furnacalisThe prokaryotic expression vector of OfurGSTd1 was successfully constructed,and the recombinant OfurGSTd1 protein was expressed in Escherichia coli.By using the affinity chromatography approach,the OfurGSTd1 protein was purified.The activity of OfurGSTd1 on CDNB,the general GST substrate,was measured,and the results showed that OfurGSTd1 had GST activity. |
PDF Full Text Request