| Spodoptera litura is a kind of omnivorous agricultural pest widely existing in the world.It has high resistance to a variety of commonly used insecticides.There are many factors that affect insect resistance.In addition to the unreasonable use of many pesticides,the impact of some exogenous factors on insect resistance can not be ignored.Herbicides and insecticides are often used together in the same plant and environment.Most of the herbicides sprayed in the farmland remain in the environment or volatilize to the air.Whether the volatiles of herbicides will affect insect resistance has not been reported.In addition,the herbivore induced volatiles(HIPVs)are released from plants when they are attacked by pests.Whether the insects can use HIPVs to enhance their resistance to insecticides remains to be studied.In this paper,Spodoptera litura was selected as the object.Firstly,the effects of Butachlor volatiles and tomato HIPVs on the drug resistance of Spodoptera litura were studied by bioassay;Then,by means of transcriptome sequencing,physiological and biochemical analysis and gene expression analysis,we analyzed the changes in the body of Spodoptera litura induced by Butachlor volatiles and tomato HIPVs respectively,explained how the resistance gene was affected,and the changes of detoxification metabolism related pathways and genes in vivo,and elucidated the mechanism of chemical volatiles induced drug resistance of Spodoptera litura.The main result is listed as follows:1.The resistance of Spodoptera litura larvae to methomyl and chlorpyrifos increased significantly when treated with butachlor volatiles 20.00% and 37.78%.Through RT-PCR detection,it was found that many olfactory related protein genes,such as OBP7,OBP8,OR12,OR55,CSP4 and CSP6,were significantly decreased in the head of Spodoptera litura by butachlor volatiles treatment.The expression of general odor binding protein GOBP2 gene was significantly reduced by 32.44%;then,through the molecular docking virtual screening,it was found that the GOBP2 protein had a good affinity with butachlor;after the GOBP2 gene was silenced by RNAi,the resistance of Spodoptera litura larvae to the insecticides methomyl and chlorpyrifos decreased significantly by 30.00% and 33.33%.2.By comparing the gene expression changes of Spodoptera litura treated with Butachlor volatiles and methomyl by transcriptome sequencing,it was found that there were five genes of the same upregulated detoxification enzyme in the midgut and seven genes of the same up-regulated detoxification enzyme in fat body,which increased the detoxification ability of Spodoptera litura.KEGG enrichment analysis showed that the up-regulated genes in the head of Spodoptera litura induced by butachlor volatiles were mainly enriched in insect hormone biosynthesis,fatty acid metabolism and unsaturated fatty acid biosynthesis signal pathway;the up-regulated genes in the midgut were mainly enriched in cholesterol metabolism signal pathway;the up-regulated genes in the fat body were mainly enriched in amino acid metabolism,carbohydrate metabolism and glutathione metabolism pathway.The ecdysone synthesis gene CYP307A1 expression of Spodoptera litura was significantly increased 138.33% by butachlor volatiles.When CYP307A1 was silenced by RNAi,the resistance of Spodoptera litura larvae to methomyl and chlorpyrifos decreased significantly 41.67% and 26.39%.3.The results of bioassay showed that the resistance of Spodoptera litura larvae to methomyl and chlorpyrifos was significantly increased by the induction of tomato HIPVs 31.67% and 37.78%.The resistance of Spodoptera litura larvae to methomyl and chlorpyrifos were significantly increased by the induction of ocimene volatile in the components of tomato HIPVs 37.33% and 28.67%.The results of transcriptome sequencing showed that tomato HIPVs induced up-regulation of forty-six detoxification enzyme genes,which increased the detoxification ability of Spodoptera litura.The results of KEGG enrichment analysis showed that the genes up-regulated in the fat body of Spodoptera litura induced by tomato HIPVs were enriched in the pathways of neuroactive ligandreceptor interaction,transport and catabolism of cell process,metabolism of other amino acids,lipid metabolism,biosynthesis and metabolism of glycan and biosynthesis of insect hormones.In conclusion,tomato HIPVs can promote the growth and development of Spodoptera litura and enhance its detoxification ability,thus enhancing its resistance to methomyl and chlorpyrifos.This paper aims to study the effects of butachlor emulsifiable oil volatiles and tomato HIPVs on the drug resistance of Spodoptera litura,and to analyze its intrinsic mechanism,so as to provide theoretical support for the integrated control of pests and lay a foundation for subsequent research. |
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