Acaricidal Activity And Mechanism Of Paeonol Against Aleuroglyphus Ovatus(Acari:Acaridae)

Objective:Aleurolyphus ovatus is one of the storage mites distributed all over the world.In practice,the long-term use of chemical acaricide will lead to the drug resistance of pest mite,damage to the non-target organisms and environmental pollution.In this study,a new plant-derived acaricide called paeonol has been expected to be prepared to deal with the above problems.In addition,the acaricidal mechanism of paeonol has been preliminarily explored,thus laying a theoretical and technical foundation for the innovative,green,safe and efficient miticides.Methods:In this paper,the contact method,fumigation method and repellent bioassay have been adopted to analyze the inhibitory effect of paeonol on A.ovatus.Furthermore,through the morphological observation,the change of skin color and toxic symptoms of mites are detected after the effect of paeonol is exerted.Moreover,the activity change data of several important enzyme systems including superoxide dismutase（SOD）,catalase（CAT）,glutathione-S-transferase（GST）,acetylcholinesterase（ACh E）,nitric oxide synthase（NOS）in the body of acaroid mites are obtained.In addition,through the joint analysis of RNA-seq transcriptome and TMT proteomics,the inhibition and acaricidal mechanism of paeonol on A.ovatus is revealed.Results:（1）The contact method and fumigation method have been adopted to determine the inhibitory effect of paeonol on A.ovatus.Also,the LC₅₀values are 9.832μg/cm²and14.827μg/cm³respectively.In other words,the acaricidal activity of contact method is better than that of the fumigation method.Normally,in the repellent experiment,when the concentration is 10 mg/ml,the repellent effect is the best;When the concentration of paeonol is lower than 2 mg/ml,the repellent effect of paeonol on A.ovatus is almost nonexistent.And after 24 hours of treatment with paeonol,the repellency rate is the highest.Besides,with the increase of treatment time and concentration,the repellent effect of paeonol on A.ovatus has been continuously enhanced with the increase of time and dose.（2）The results of toxicity observation showed that 20%and 42%of mites showed KD（Knock down）type after 5 min and 10 min of 12 mg/ml paeonol treatment.Meanwhile,no mites are IM（Immobilizer）type;While after 90 minutes of treatment,90%of the mites showed KD type and 7%of mites showed IM type.In general,the A.ovatus treated with paeonol usually shows the typical neurotoxic symptoms including the excitement,convulsion and paralysis.Furthermore,through the observation of stereoscopic microscope and scanning electron microscope,the epidermis of A.ovatus treated with paeonol turned brown with some shrinkage.（3）After the action of paeonol,the enzyme activity in mites changed.Compared with the control group（acetone group）,the activity of protective enzyme named SOD in the mites in the experimental group is lower.As for CAT,the activity of CAT enzyme in the experimental group is higher than that in the control group（acetone group）,indicating that after paeonol treatment,the activity of CAT is activated,while the activity of SOD enzyme is inhibited.In addition,compared with the control group（acetone group）,the activity of GSTs in the body of mites treated with paeonol is higher,indicating that the enzyme activity of GSTs is activated.Moreover,compared with the control group（acetone group）,the activity of nerve effector enzyme named ACh E in the body of mites treated with paeonol is lower,while the activity of NOS is higher,indicating that the activity of ACh E enzyme is inhibited,while the activity of NOS enzyme is activated.（4）The results of the combined analysis of transcriptome and proteome show that after the effect of paeonol on A.ovatus,the 49 genes of A.ovatus show the consistent changes in transcriptome and protein levels,that is,the transcriptome and protein levels of 23 genes show a downward trend,while the transcriptome and protein levels of the other 26 genes show an upward trend.In general,the proteins encoded by these genes are mainly related to hydrolase,serine peptidase,antioxidant enzyme and oxidoreductase.At the same time,these enzymes mainly include flavin monooxygenase（FMO）,acyl-Co A dehydrogenase family member 8（ACAD8）,glutathione peroxidase（GPX）,cathepsin L（CTSL）and serine protease 1（PRSS1）.Among them,the activity of hydrolase named CTSL has been increased,the activity of serine peptidase named PRSS1 has been increased,the activity of antioxidant enzyme named GPX has been decreased,and the activity of oxidoreductase named ACAD8 and FMO has also been decreased.Conclusion:The paeonol can be utilized to inhibit the activity of A.ovatus.Moreover,the inhibition effect of contact method on activity is better than that of fumigation method.In addition,the repellent effect of paeonol on A.ovatus will increase with the increase of time and dose.By destroying the dynamic balance of protective enzyme,the detoxification enzyme and nerve effector enzyme in A.ovatus,the paeonol can be employed to affect the normal physiological metabolism of A.ovatus,thus causing the toxic effects on mites.Moreover,the combined analysis of transcriptome and protein showed that the paeonol can be adopted to affect the activities of hydrolase,serine peptidase,antioxidant enzyme and oxidoreductase in mites,thereby leading to the death of mites.Therefore,paeonol can be used as an acaricide to control storage mite A.ovatus.