Effects Of Graphene Oxide On The Growth, Development, Reproduction And Intestinal Microorganisms Of Fall Armywor

Spodoptera frugiperda（J.E.Smith）,commonly known as fall armyworm（FAW）,is a major migratory pest that invaded China in 2019,posing a severe threat to the production of major and economical crops.At present,chemical control method is still the main methods of controlling FAW.However,the extensive use of chemical insecticides has led to the higher resistance.Therefore,mixing pesticides with other substances that can interfere with pests will effectively inhibit the development of resistance.Graphene oxide（GO）,an oxide of graphene,has a certain effect on the development and reproduction of insect pests.To explore the effect of GO on FAW,the age-instar bisexual life table was used to investigate the impacts of nano-GO on the growth,development and reproduction of FAW.Moreover,the effects of GO on the composition,function and antibiotic resistance genes of larval intestinal microbes of FAW were analyzed based on the metagenomic sequencing method.Our findings provided a novel perspective and direction for the development of effective insecticides for FAW.The major research outcomes of this study were as follows:1 Effects of GO on growth,development and reproduction of Spodoptera frugiperdaThe development and reproduction of the FAW,which were reared on artificial diets containing different concentrations of nano-GO,were determined based on age-stage,two-sex life table analysis.The results showed that GO had adverse effects on FAW.Compared with the control,the durations of the egg and 1^st,2^nd,and 6^th instar larva were prolonged with increasing GO concentrations.However,the lifespans of male and female adults were shortened with increasing GO concentrations.Weights of FAW pupa supplied with GO-amended diets decreased by 0.17-15.20%compared to the control.Intrinsic growth（r）,limited growth（λ）,and net reproductive rates（R₀）of FAW feeding on GO supplemented diets were significantly lower than the control(0.154 d^-1,1.16 d^-1and 329.37),while mean generational periods（T）were significantly longer than the control（37.41 d）.In the concentrations of 0.5 mg/g,the r,λ,R₀and T were 0.141 d^-1,1.15 d^-1,232.37,and 38.47 d respectively.In the concentrations of 1mg/g,the r,λ,R₀and T were 0.132 d^-1,1.14 d^-1,214.05 and 40.38 d respectively.While they were 0.133 d^-1,1.14 d^-1,170.36 and 38.42 d respectively in the concentration of 2 mg/g.In conclusion,GO could prolong the developmental time of FAW,decrease fecundity,and led to a decline in the population.2 Effects of GO on the expression of vitellogenin gene and vitellogenin receptor gene of Spodoptera frugiperdaIn explore the effect of GO to the reproduction of FAW,the expression of vitellogenin（Vg）and its corresponding receptor（Vg R）were analyzed under GO treatment.The results showed that the expression levels of Vg and Vg R were significantly affected at time and concentration after FAW was fed GO-treated diets with varying concentrations,and different concentrations of GO had a significant impact on the expression levels of Vg and Vg R.On the third day,the expression level of Vg in female adult FAW ingesting a concentration of 2 mg/g was significantly higher than that of other treatment and control groups（P<0.05）.On the sixth day,the expression level of Vg R gene was significantly down-regulated compared to the control group（P<0.05）under all GO treatments,while the expression level of Vg R in female adult FAW at the 0.5 mg/g and 1 mg/g treatment groups was significantly higher than that of the control group.On the eleventh day,the expression level of Vg R gene increased,but the expression level of Vg gene decreased.In conclusion,GO treatment might have a certain impact on the reproduction of FAW,causing abnormal expression of Vg and Vg R genes.3 Effects of GO on intestinal microbial community structure,function and resistance genes in Spodoptera frugiperdaThe effect of GO on the gut microbiota composition and abundance in FAW was studied.The larvae of FAW were fed different concentrations of GO,of 0.5 mg/g,1mg/g,and 2 mg/g,and feeding the normal artificial diet was set as the control.And,the FAW recoved to normal artificial diet were set as 0.5 mg/g recovery,1 mg/g recovery,and 2 mg/g recovery.It was observed that the intestinal microbial community structure of FAW was significantly changed by GO treatment.The relative abundance and diversity of gut microbes increased with GO treatment.The bacterial community analysis revealed changes in the distribution of dominant bacterial genera.The relative abundance of Firmicutes increased at 0.5 mg/g and 0.5 mg/g recovery,and similarly at1 mg/g and 1 mg/g recovery,but decreased at 2 mg/g and 2 mg/g recovery.The relative abundance of Proteobacteria exhibited a decreased at 0.5 mg/g,0.5 mg/g recovery,1mg/g and 1 mg/g recovery,but increased in 2 mg/g and 2 mg/g recovery.In addition,the abundance of three dominant bacterial taxa,namely Lactobacillaceae,Enterococcaceae and Leuconostocaceae was found to be influenced.The results of this study indicate that GO treatment significantly affects the composition and abundance of FAW gut microbiota and the abundance of gut microbiota has not fully recovered to its original level even the diet recovered to the normal.Additionally,by sequencing the gut microbiome metagenome and performing metabolic analysis on the metagenome of FAW fed with different concentrations of GO,it was found that carbohydrate metabolism is the most abundant functional category.After feeding on GO,the carbohydrate metabolism,amino acid metabolism,biosynthesis of secondary metabolites,energy metabolism,and abundance of terpenoids and polyketides metabolites in FAW were found to decreased to certain extent,while other metabolic pathways showed corresponding increases.Additionally,multiple resistance genes were discovered,among which efr A,efr B,rpo B2,rpo B,efm A,lmr D,van RC,Pmr E,AAC（6’）-Iih,AAC（6’）-Iid,dfr E,Arl R,Tet A,van RA,Van RI,Lsa A,AAC（6’）-Ii,Mac B,and van RG,and tet（W/N/W）exhibited resistance to different types of antibiotics.In conclusion,GO has certain inhibitory effects on the growth,development,reproduction and reproduction related genes of FAW,and the inhibitory effects increased with the increase of concentration.GO feeding could change the intestinal microbial community structure and resistance gene composition of FAW.The results indicate that GO can provide a new perspective and direction for the development of novel prevention and control agents for FAW.