Toxic Effect And Mechanism Of Symbiont Of Achnatherum Inebrians-Epichlo(?) Endophytes On Acyrthosiphon Pisum

Achnatherum inebrians is the dominant species of grassland in northern China and an important poisonous grass.However,from a systematic perspective,it has many irreplaceable positive effects,and the previous researchers had conducted many innovative achievements.How to use efficiently it in pest control and reveal the corresponding mechanism is of great significance for its resource utilization,but the relevant research has not been reported.In addition,the pea aphid(Acyrthosiphon pisum)is an important pest of aphids and one of the most important pests in the world,which is of far-reaching significance for its scientific control.However,the use of a large number of chemical pesticides leads to serious environmental pollution and a series of problems.Using biological control methods to control pea aphids will be the first choice of green agriculture,and the use of plant-derived pesticides is one of the biological control methods.Therefore,aiming at the objective attributes of the epichlo(?)endophytes symbiosis of A.inebrians,combined with the ecological concept of turning waste into treasure and sustainable development,this study selected pea aphid as the model organism for the study of mouthparts,and carried out a series of research contents,in order to explore the feasibility of the epichlo(?)endophytes symbiosis of A.inebrians as a plant-derived insecticide,and reveal the toxic effect and toxic mechanism of the aqueous extract of the epichlo(?)endophytes symbiosis of A.inebrians on pea aphid.The main research results are as follows:1.There were significant differences in reproduction and life table parameters after contact with pea aphid by the epichlo(?)endophytes symbiosis of A.inebrians at seedling stage(P<0.05).The mortality of endophyte-infected inebrians(E+)aqueous extract in seedling stage was significantly higher than that of endophyte-free inebrians(E-)and control(CK)(P<0.05),up to 74.32%,and the idiophase was shortened by2.74d and 2.91d;The average fecundity decreased by 8.38 and 12.14;The reproductive decreased by 68.72%and 79.78%,the intrinsic rate of increase(r_m)and net reproductive rate(R₀)were the lowest(r_m=0.080d^-1)and(R₀=1.881),the doubling time(Dt)was prolonged(Dt=8.710d).At the same time,E+aqueous extract at seedling stage had significant effect on the biological characteristics and reproduction of pea aphid offspring(P<0.05).Compared with E-and CK,the developmental duration was prolonged by 0.86d and 1.88d,the weight difference was increased by9.52%and 0%,the mean relative growth was reduced by 20.52%and 24.52%,the average fecundity was reduced by 12.38 and 14.88,the reproductive was reduced by40.65%and 52.90%,the net reproductive rate(R₀=3.712)was the smallest,and the doubling time(Dt=6.150d)was prolonged.2.The E+and E-aqueous extract at seedling stage were detected and analyzed by metabolomics technology.The results showed that a total of 2835 metabolites and1667 differential metabolites were annotated,of which 866 were up-regulated and 801were down regulated.Through the analysis of KEGG pathway,it was found that three pathways were significantly enriched in carbohydrate metabolism,indole alkaloid biosynthesis,phenylalanine,tyrosine and tryptophan biosynthesis.3.The treatment of E+aqueous extract at seedling stage affected the nutrient content and physiological and biochemical indexes of the host plant Vicia faba leaves,and then indirectly affected the nutrient and physiological and biochemical indexes of pea aphid.After E+treatment,the contents of digestive,aminotransferase and detoxifying enzymes in pea aphids were related to the nutrient content and enzyme activity of Vicia faba leaves,and this correlation were changed with different treatments.4.After the treatment of pea aphid with aqueous extract at seedling stage,the results of metagenomics sequencing showed that Proteobacteria was the dominant bacteria in pea aphid,and the symbiotic Buchnera was the dominant bacteria in pea aphid.E+treatment increased significantly the abundance of Serratia,Aquifex and Escherichia,but also reduced the abundance of Buchner,and carbohydrate metabolism and amino acid metabolism.5.After the pea aphid was different treatments at seedling stage,a total of 31858single genes of pea aphid were found in the transcriptome sequencing results,of which 31640 were from the genes annotated in the database Nr and 266 were from the new genes annotated in the database.Based on the phenotype of mortality,53detoxification enzyme genes were found;The differentially expressed genes among different treatments,4 epidermal protein genes,4 cathepsin B genes,6 fatty acid synthase genes and four aminopeptidase N genes,were identified;At the same time,the expression levels of CTSB,LGMN and ANPEP genes were down-regulated,while the expression level of transaminase gene in lysosomal related pathway was up-regulated;KEGG pathway analysis showed that the differentially expressed genes were significantly enriched in nutritional metabolism and detoxification metabolism,including of glutathione metabolic pathway,lysosome,biosynthesis and detoxification of phenylalanine,tyrosine and tryptophan.To sum up,there are 39 different metabolites in the aqueous extract of E+at seedling stage compared with the E-.After it is instantaneously treated with pea aphid,the mortality increases,the reproduction rate decreases,and the digestive enzymes,aminotransferases and detoxification enzymes have changed significantly.At the same time,the abundance increased of Serratia,Aquifex and Escherichia,and the abundance reduced of Buchner.It was found that the disturbed genes of pea aphid related to the growth,reproduction and detoxification by E+were 53 detoxification enzyme genes,4 epidermal protein genes,4 cathepsin B genes,6 fatty acid synthase genes and 4 aminopeptidase N,which reduced the metabolism of carbohydrates and amino acids,and disturbed or destroyed the physiological,microecological balance and functional gene expression of pea aphid to achieve the toxic effect and pest control effect on pea aphid.Therefore,drunken horse grass has great potential to develop botanical insecticides.