Effects Of Arsenophonus And Wolbachia On Stress Resistance Of Nilaparvata Lugens (Stal)

The brown planthopper,Nilaparvata lugens(St(?)l)(Hemiptera:Delphacidae)is a destructive rice pest which contains a variety of symbiotic bacteria.Arsenophonus and Wolbachia are common symbiotic bacteria which have been found to have an impact on the host’s reproduction,other than this,does the endosymbionts have impact on the host’s resistance to stress?and what’s the impact of the co-infection of symbiotic bacteria?In this paper,we established different symbiotic strains of brown planthopper from the population collected in De’an,Jiangxi province,China,and then investigated the stability of Arsenophonus and Wolbachia’s combined infection,and compared the resistance of different strains of N.lugens infected with different symbionts to insecticidal fungi,chemical insecticides,and high and low temperature.The results can not only enrich the theory of co-evolution relationship among endosymbionts and hosts,but also be benefit to the control of brown planthoppers.(1)The stability of Arsenophonus and Wolbachia in brown planthopper:The infection of four symbionts in the brown planthopper collected from De’an,Jiangxi province was detected,and the strains of N.lugens infected with different symbionts were established to analyze the stability and function of the symbiotic bacteria.The results showed that the brown planthopper was infected with two symbiotic bacteria,Arsenophonus and Wolbachia,and was not infected with Serratia and Acinetobacter.Single-infection strains and double-infection strains of Arsenophonus and Wolbachia,and symbiotic bacteria-free strain were then established.In the double-infection strain,the proportion of double-infection could not be stabilized at 100%.After 8 generations of vertical transmission,the double-infection incidence decreased to 80%.The results indicated that Arsenophonus and Wolbachia could not be transmitted to all individuals of brown planthoppers,but the co-infection rate remained at a high level.(2)The effect of Arsenophonus and Wolbachia on the resistance of brown planthopper to Isaria javanicus:The effect of Arsenophonus and Wolbachia on resistance to insecticidal fungi was compared using I.javanicus spore suspension spraying method.The difference in sensitivity to 2×10~6 spores/m L and 8×10~6spores/m L I.javanicus spores among different strains was investigated.The results showed that,compared with the control without fungi,the individuals of brown planthoppers treated with fungi had obvious symptom of fungal infection,and the brown planthoppers infected with Arsenophonus had stronger resistance to I.javanicus than that without the endosymbiont,and this resistance was not affected by Wolbachia infection,indicating that Arsenophonus in brown planthoppers can help the host to resist the infection of the insecticidal fungus I.javanicus.(3)The influence of Arsenophonus and Wolbachia on the resistance of Nilaparvata lugens to chemical insecticides:Two concentrations of trifluoropyrimidine,dinotefuran,nitenpyram and pymetrozine were used to spray different strains of N.lugens.The results showed that,the mortality of brown planthopper without symbiotic bacteria was always higher than that of the other three strains after treatment with 0.3125mg/L and 0.625mg/L trifluoropyrimidine or 0.625mg/L nitenpyram,indicating that both Wolbachia and Arsenophonus can increase the host’s resistance to chemical insecticides,and the protective function was not affected by co-infection of the two endosymbionts.(4)The influence of symbiotic bacteria on the resistance of brown planthopper to high and low temperature:The brown planthopper with different symbiotic bacteria was subjected to high temperature and low temperature stress,and it was found that,there was no difference in the resistance to high and low temperature among various strains of N.lugens,indicating that the symbiotic bacteria Arsenophonus and Wolbachia did not affect the resistance of brown planthopper to high and low temperature.(5)Differences in the expression levels of detoxification enzyme genes in different strains of N.lugens:Appling the fluorescence quantitative PCR techniques,the differences in the expression levels of glutathione S-transferase gene and cytochrome P450 gene in four strains were compared.The results showed that the composition of endosymmbionts had no significant effect on the expression of GST gene of brown planthopper.It was also found that,the expression levels of P450 genes in different strains of N.lugens were different,and these differences were related to the types of genes and the species of symbiotic bacteria.The expression of CYP425A1,CYP3115A1,CYP4DD1 and CYP303A1 were significantly down-regulated in the Wolbachia strain alone and the combined infection strain.The expression levels of CYP306A2 and CYP6AY1 were significantly up-regulated in the Wolbachia-infected strain.Single infection of Arsenophonus reduced the expression of CYP425A1,CYP3115A1,and CYP4DD1.