Effects Of Sublethal Dose Of Spinosad On Development And Physiological Metabolism Of Helicoverpa Armigera Larvae

In this study,the larvae of Helicoverpa armigera were used as the research subjects,and the effects of spinosad on the growth and development of the larvae,hormone,lipid metabolism and immune metabolism pathway were investigated by feeding them diets containing different sublethal doses of Spinosad.Statistical analysis,fluorescence quantitative PCR,ELISA and enzyme activity detection were used to analyze the physiological indexes of H.armigera larvae fed with spinosad,such as insect weight and mortality.The titers of hemolymph ecdysis hormone and juvenile hormone and the transcriptional changes of epidermal transcription factors HR3 and Kr-hl were measured.At the same time,the changes of triglyceride(TG)content and the transcription of cholesterol regulatory element binding protein(SREBP),protein kinase(PKA)and fatty acid synthase(FAS)were studied at the physiological,biochemical and molecular levels.Calcineurin(CaN)activity and immune-related antimicrobial peptide and lectin gene transcription were detected.The molecular characteristics of tachykinin TK in the midgut of H.armigera at different stages of development were analyzed.Meanwhile,the changes in the transcription levels of tachykinin TK and Kr-hl were compared after the feeding of spinosad.The relationship between TK and JH was further detected by injecting TK/dsTK and dsTKR into the body of H.armigera.The main results are as follows:1.The toxicological curve of the third instar larvae of H.armigera was est ablished using the feed mixing method.The artificial feed mixture method was used to bioassay the first larvae of the third instar of H.armigera,and the virulence curve of spinosad to the larvae of H.armigera on the 7th day was y=3.2676x+6.5711.2.After the sublethal dose of spinosad was fed to the H.armigera,the growth and development of the H.armigera was significantly inhibited.After the third instar larvae of the H.armigera were fed with a sublethal dose of spinosad,the indicators of each instar were investigated within 7 days.Compared with the control,it was found that the weight of the H.armigera became lighter,the molting time was longer,the developmental period was prolonged,and the deformity rate increased,The pupation rate and emergence rate are reduced.3.Changes in the titers of H.armigera hormones(20E,JH)and the transcription levels of transcription factors(HR3,Kr-h1)after feeding the H.armigera at sublethal doses of spinosad.After the H.armigera took a sublethal dose of spinosad,its ecdysone titer decreased and the juvenile hormone titer increased compared with the control;at the same time,the transcription level of ecdysone transcription factor HR3 decreased significantly,and the juvenile hormone transcription factor Kr-h1 transcription level was significantly increased.4.The transcription level of TK in the midgut tissue at different developmental stages,and the relationship between TK and JH in H.armigera.After the third instar larvae of H.armigera were fed spinosad,the TK and Kr-h1 transcription levels of the midgut tissue of the H.armigera increased significantly at different feeding time points compared with the control.After TK injection,compared with the control,the Kr-h1 gene was significantly increased;after the intervention of TK,the Kr-h1 gene was significantly decreased.5.After spinosad was fed,the metabolism-related indexes in the larvae of H.armigera and the transcription of genes downstream of fat synthesis and metabolic pathways changed.After feeding spinosad,the enzyme activities and genes related to the fat metabolism signaling pathway of the three main metabolic tissues(midgut,fat body,epidermis)of H.armigera changed at different feeding time points,and the triglyceride content decreased,and the fat synthesis gene decreased,Fat metabolism-related genes have undergone significant changes.6.After feeding sublethal doses of spinosad,the immune-related genes of the H.armigera are down-regulated,which has an impact on the immune metabolic pathways of the H.armigera.The CaN enzyme activity and related genes of the immune signaling pathway in the fat body tissue of H.armigera at different feeding poisoning time points also changed significantly.In the immune signaling pathway,calcineurin enzyme activity,antimicrobial peptide gene transcription level and lectin genes Lectin4,Lectin5,and Lectin6 were all changed.There is an upward trend.