Toxicological Mechanism Of α-terthienyl On Lymantria Dispar Larvae

Due to the irrational use of chemical pesticides for a long time,the"3R"problem becomes more and more serious,and people gradually realize the importance of plant source pesticides.In order to explore the insecticidal activity and mechanism ofα-terthienyl against Lymantria dispar larvae,this study used feed mixture method,spectrophotometry,HE staining method,real-time quantitative PCR analysis,16S r RNA sequencing,and other methods to determine the survival rate ofα-T against L.dispar larvae,nutritional feeding indicators,nutrient content,midgut antioxidant enzyme activity and redox system indicators,midgut antioxidant enzyme activity and m RNA expression levels,the expression levels of JAK-STAT signaling pathway and mitochondrial apoptosis pathway and the influence of gut bacteria in larvae.The toxicological mechanism ofα-T against L.dispar larvae was analyzed,and the main conclusions were as follows:（1）α-T had good toxic activity against the 3^ndinstar larvae,and the 72-h sub lethal concentration(LC₂₀)and the lethal medium concentration(LC₅₀)were 0.020μg/m L and 0.178μg/m L,respectively.α-T could significantly reduce the weight growth of L.larvae（P<0.05）,and the growth inhibition rates of L.dispar larvae treated with LC₂₀and LC₅₀concentration for72 h were 44.26%and 62.29%,respectively.α-T could reduce the contents of four nutrients（soluble protein,carbohydrate,trehalose and lipid）in L.dispar larvae,and the lipid content decreased the most（62.68%）.After 72 h of treatment withα-T,the midgut tissue of the 3rd instar larvae of L.dispar was significantly damaged,andα-T could cause significant pathological changes in the midgut of L.dispar larvae,inducing apoptosis of midgut cells and causing midgut damage.（2）α-T inhibited the activity of Catalase（CAT）,Superoxide dismutase（SOD）and Peroxidase（POD）in the midgut of 3^ndinstar larvae.And can significantly down-regulate the gene expression levels of CAT and SOD.Underα-T stress,MDA content and H₂O₂content in L.dispar larvae were significantly increased,while T-AOC was significantly decreased（P<0.05）.The results indicated thatα-T treatment of the 3^ndinstar larvae inhibited the activity of antioxidant enzymes and m RNA expression,resulting in oxidative stress in the midgut of L.dispar.（3）The m RNA expression levels of JAK and STAT genes in L.dispar larvae were decreased byα-T,and the m RNA expression levels in treatment group were decreased significantly after 72 h of treatment.The expression levels of mitochondrial apoptosis pathway genes Cyt-c,Caspase3 and Caspase9 in midgut of L.dispar larvae were significantly up-regulated afterα-T induction（P<0.05）.α-T inhibited JAK-STAT signaling pathway in midgut of L.dispar larvae,and activated mitochondrial apoptosis pathway to induce apoptosis in midgut cells of L.dispar larvae.（4）α-T induced changes in the structure,abundance and function of the gut bacteria of L.dispar larvae.Based on 51 OTU,the functional abundance of the gut bacteria G（transport and metabolism of carbohydrates）was up-regulated,while the function of L（replication and repair）was down-regulated.α-T can change the abundance of functional bacteria C（energy production and conversion）and I（lipid transport and metabolism）,which further indicates thatα-T can damage the gut of L.dispar larvae.α-T has toxic effect on the 3^ndinstar larvae of L.dispar,the effects of nutrient intake and nutrient content of L.dispar larvae,the effects of oxidative stress in midgut,the effects of m RNA expression in midgut JAK/STAT pathway and mitochondrial pathway,and the effects of intestinal bacteria.It is concluded thatα-T can induce apoptosis in midgut oxidative stress of L.dispar larvae.This study can provide the basis for the development and utilization ofα-T and the control of L.dispar.