| The essential oil of Melaleuca alternifoliais obtained from the fresh leaves and branches of Melaleuca alternifolia(Myrtaceae,Melaleucal)plants,which has obvious antibacterial and broad-spectrum bactericidal activities.Nowadays it is widely used in the medical and daily chemical field.In previous studies,the main components of M.alternifolia essential oil was analyzed and found that M.alternifolia essential oil and its main component terpinen-4-ol had significant insecticidal activity on stored grain pests in our lab.However,its insecticidal effect on Myzus persicae has not been reported.Therefore,this paper determined the bioactivity of M.alternifolia essential oil against M.persicae,and the effect of M.alternifolia essential oil on M.persicae gene expression.Then,the binding mode of terpinene-4-ol and its target based on computer aided drug design technology was studied.In addition,the expression pattern of related genes in response to terpinene-4-ol fumigation stress in M.Persicae were studied by transcriptome analysis,providing a preliminary basis for further study on the molecular mechanism of insecticidal effect of terpinen-4-ol on aphids.The main results are described as follows:1.Insecticidal activity of M.alternifolia essential oil on Myzus persicaeThe results of bioassay showed that M.alternifolia essential oil had significant effect on repelling and contact activity against M.persice,and a patterm of significant significant dose-and time-dependent inhibitory effect was observed.The deterrence index(DI)was 0.75 after the aphids treated with 2 g/L M.alternifolia essential oil for 48 h.The contact mortality of M.aternifolia oil on M.persice was 92.58%at 4 g/L for 72 h post treatment.The LC30 and LC50 values of M.alternifolia essential oil against M.persicae were 0.08 and 0.36 g/L,respectively,as determined by Probit analysis.The results demonstrated that M.alternifolia essential oil had good insecticidal activity.2.Effect of M.alternifolia essential oil on gene expression in Myzus persicaeM.persicae was continuously treated with LC30 and LC50 doses of M.alternifolia essential oil.The expression levels of HSP60,OSD,TOL,ANT and FPPS1 were detected by qRT-PCR.The results showed that four out of the five genes(OSD,ANT,HSP 60 and FPPS ?)showed up-regulation after treated with LC50 dose of M.alternifolia essential oil,while the expression of TOL was higher when treated with LC30 dose than that with LC50 dose;ANT gene expression level was inhibited at low dose(LC30)exposure and induced up-regulation at LC50 dose.3.Study on binding mode of terpinene-4-ol and its target based on computer aided drug design technologyThe major components of M.alternifolia oil(terpinen-4-ol)was docked and MD simulated into the related proteins of the selected genes(OSD,FPPS ?,and HSP 60)to explore ligand-protein modes of interactions.The results showed that the C-coefficients of terpinene-4-ol on OSD,FPPS ? and HSP 60 were 5.23,4.55 and 4.42,respectively,indicating that the binding affinity of terpinen-4-ol on OSD was slightly higher than that of FPPS ? and HSP 60.The binding free energy of terpinen-4-ol to OSD,FPPS ? and HSP 60 was-10.34,-9.43 and-7.94 kcal/mol,respectively,which was calculated by MMGB/PBSA.These results provided a foundation for the study of structure-activity relationship of terpinen-4-ol.4.Insecticidal activity of constituents of M.alternifolia essential oil and RNA-Seq analysis of M.persicae transcriptome in response to terpinen-4-ol fumigationThe activity of terpinen-4-ol and ?-terpinene were evaluated for their insecticidal potential against M.persicae using fumigant assay.After treated with 3 ?L/L terpinen-4-ol and ?-terpinene for 72h,the mortality of M.persicae were 96.3%and 85.74%respectively.While treated with 6 ?L/L ?-pinene and ?-caryophyllene,M.persicae mortality were 83%and 65.5%,respectively for 72 h fumigation treatment.The fumigation activity of ?-pinene and ?-caryophyllene has a good synergistic effect on terpinen-4-ol and ?-terpinene,and the mixed use of ?-pinene and terpinen-4-ol has the best effect on the insecticidal effect of peach aphid with a mortality rate of 80%.Therefore,the mixture of terpinen-4-ol and ?-pinene and other terpenes has a good application prospect in the control of peach aphid.Transcriptomic analysis of the response to terpinen-4-ol was performed after treatment with LC30 terpinen-4-ol in M.persicae.It was found that after terpinen-4-ol treatment,there were 922 differentially expressed genes in M.persicae,among which 399 genes were up-regulated and 523 genes were down-regulated.According to Go analysis,most of these differentially expressed genes are related to cell process,metabolic process,catalytic activity and membrane part.The results of KEGG pathway analysis showed that the different genes were enriched in the mitochondrial electron transport and metabolic pathway.This provides a preliminary basis for further study on the molecular mechanism of terpinen-4-ol on peach aphid. |
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