Study On The Mechanism Of Monoterpene Chiral Compound Mla In Megalurothrips Usitatus(Bagnall) And Drosophila Melanogaster

Plant essential oils(EOs)are kinds of major members of biopesticide,which are important content in the field of agriculture and food science.The constituents of EOs are complex,and the main components are sesquiterpenoids and monoterpenoids.EOs can play an important role in plant protection,which is a substitute for synthetic insecticides.Among them,monoterpenoids are the main components of aromatic plant essential oils and also high efficient to insects.In this paper,we studied the acute toxicity and stereoselectivity of monoterpenoids chiral compounds(+)-R-mla、(-)-S-mla to Megalurothrips usitatus(Bagnall)and Drosophila melanogaster.Moreover,the mechanism of(+)-R-mla.(-)-S-mla on the D.melanogaster were explored.The main results are as follows,(1)The toxic of chiral compound(+)-R-mla、(-)-S-mla to M.usitatus(Ba.gnall)and D.elanogaster were stereoselective,which(+)-R-mla has highly fumigation activity.The results of acute toxicity indicated that the median lethal concentration(LC50)of(+)-R-mla and(-)-S-mla to Drosophila elanogaster were 0.079 μL/L(95%confidence limits:3.92-4.21,R2=0.875)and 0.119 μL/L(95%confidence limits:0.065-0.318,R2=0.792),respectivity,after 24 h exposure.(2)The crawling assay of D.melanogaster induced by(+)-R-mla、(-)-S-mla were detected.The results of crawling height of D.melanogaster was increased 38.3%after exposed to 0.024 uL/L of(+)-R-mla in the third crawling test.It was decreased 1.17 fold after exposed to 0.192 uL/L of(+)-R-mla in the third crawling test The result of crawling height was decreased 1.08 fold after exposed to 0.192 uL/L of(-)-S-mla in the fifth crawling test.It was no regular effect induced by low concentrations of(-)-S-mla.(3)Comparison of differential gene express of mRNA were performed by transcriptome sequencing.The three genes of up regulated 20 folds were related to cytochrome P450,one gene was related to peroxidase and one gene was related to retinol dehydrogenase.It were fifteen genes that up regulated 10 folds and seven of them were associated function,which were related to cytochrome P450(3 genes),and glutathion s transferase(2 genes).It were fifty-nine genes that up regulated 5 folds which were related to thirty-three metabolic pathway including lipid metabolism(1 1 gens),metabolism of amino acid(5 genes),contributing to carbohydrate metabolism,biosynthesis of other secondary metabolites,cofactor and vitamin metabolism e.g.(4)The content of cytochrome P450 enzyme in D.melanogaster were increased 4.78 folds induced by 0.024μL/L group of(+)-R-mla,which was significant different(p<0.01)compared with control group.It was increased 2.41 folds induced by 0.012μL/L group of(+)-R-mla,which was significant different(p<0.05)compared with control group.The content of cytochrome P450 enzyme in D.melanogaster were increaseat 2.76 folds by 0.012μL/L group of(-)-S-mla,which was significant different(p<0.05)compared with control group.The contents of peroxisase(POD)and glutathion-stransferase(GST)had not significantly changed.(5)The content of free amino acids in M.usitatus(Bagnall)and D.elanogaster fumigated with(+)-R-mla、(-)-S-mla were detected.The results showed that content of glycine on D.melanogaster and M.usitatus(Bagnall)had significantly increased comparaed with the control with dose-response relationship,respectively.The change of content of glycithe on M.usitatus(Bagnall)decreased with the increasing concentrations,suggested an negative correlation between the increment and the treatment concentrations(R2=0.920).The change of content of glycithe on D.elanogaster increased with the increasing concentrations,suggested an positive correlation between the increment and the treatment concentrations(R2=0.617).The results proposed that the content of glycine was related to the toxicity of(+)-R-mla、(-)-S-mla.(6)Site land site2 binding sites were found by molecular docking technique(autodock vina)to simulate the docking of compound(+)-R-mla and Glycyl.tRNA synthetase.The binding energy of(+)-R-mla was higher than that of(-)-S-mla,which were-5.6 and-4.9,respectively.(7)The interaction test between small molecules and protein was performed in this study.The results indicated that(+)-R-mla、(-)-S-mla can interact with Glycyl-tRNA synthetase.The KD values of(+)-R-mla and Glycyl-tRNA synthetase was 1.08 X 10-4(R2=0.799).The KD values of(-)-S-mla and glycine-tRNA synthase was 4.37×10-5(R2=0.678).This results proposed that(+)-R-mla and Glycyl-tRNA synthetase was more reliable than(-)-S-mla.(8)D.melanogaster which fed with com agar medium containing 0.001、0.002 and 0.003g/mL concentrations of glycine antagonist strychnism,were fumigated with(+)-R-mla、(-)-S-mla for 24h,The results showed that LC50 values for(+)-R-mla、(-)-S-mla on D.melanogaster fed with strychnism showed no significant difference from that of the control,which indicated that the toxie mechanism of(+)-R-mla、(-)-S-mla were different from strychnism.