The Effect Of Bt Synergistic Protein On The Intestinal Bacterial Diversity And BBMV Binding Ability Of Plutella Xylostella Larvae

The relationship between the insect gut microbial community and the life activities of the host is inseparable.The gut microbes enhance the host’s adaptability to the environment by participating in the host’s metabolic activities and immune activities.Recent studies have shown that insect gut microbes interact with insects.The formation of resistance to indoxacarb,fenxazone,and biological pesticides such as Bt is related.Plutella xylostella mainly damages cruciferous crops.It is one of the most influential pests in the world.The resistance of P.xylostella is developing rapidly.At present,P.xylostella has developed resistance to 97 insecticidal active ingredients,among which Including the biological insecticide Bacillus thuringiensis.This article takes the diamondback moth as the research material,and intends to explore different strains/population by screening the Cry1 Ac sensitive and resistant strains of the diamondback moth,and the types of intestinal bacteria that can be cultivated in the field population,and testing the differences in the physiological and biochemical functions of the intestinal bacteria that can be cultivated.The relationship between the types and functions of the intestinal bacteria of P.xylostella and its resistance to Bt.On this basis,according to the results of preliminary laboratory research,the effect of Bt synergistic proteins PxALP and PxCAD1,which can significantly improve the insecticidal activity of Cry1 Ac on P.xylostella,has been studied on the types of cultivable intestinal bacteria of P.xylostella.At the same time,we explored the effects of PxALP and PxCAD1 on the BBMV binding ability of P.xylostella,the protease hydrolysis ability of the midgut and the expression of some immune genes PGRPs.The results of this study are as follows:1.The study found that the Cry1 Ac sensitive and resistant strains of P.xylostella,and the intestinal cultivable bacterial strains of the field populations are very different,and the Cry1 Ac sensitive strains have the largest number of intestinal bacteria,and the number of bacterial species extracted from the field population is the second.However,the bacteria cultured from the intestinal tract of Cry1 Ac sensitive strains all belong to the Proteobacteria,and the types of bacteria that can be cultured in the intestinal tract are relatively single.The difference between Cry1 Ac resistant strains and sensitive strains is mainly in Firmicutes.There are also certain differences in the physiological and biochemical functions of the intestinal cultivable bacteria between the above-mentioned different diamondback moth strains/population.The study found that the growth of Carnobacterium maltaromaticum,Enterococcus mundtii,Staphylococcus warneri and Staphylowecoccus epidermidis isolated from Cry1 Ac resistant strain were affected by Cry1 Ac toxin.In the experiment of the effect of the synergistic protein PxALP or PxCAD1 on the intestinal bacterial diversity of the diamondback moth,there are certain differences in the types of bacteria that can be cultivated in the intestine of the diamondback moth larvae after the treatment of the synergistic protein PxALP or PxCAD1.The addition of PxALP or PxCAD1 did not significantly affect the cultivable bacteria in the intestine of P.xylostella larvae.2.It is found that PxALP can promote the combination of P.xylostella BBMV and Cry1 Ac to a certain extent,but the promotion effect is not significant,and shows a weakening trend as the concentration of Cry1 Ac increases.PxCAD1 inhibits or hinders the combination of BBMV and Cry1 Ac of P.xylostella to a certain extent,but the effect is not significant.Therefore,PxALP and PxCAD1 have no significant effect on the combination of P.xylostella BBMV and Cry1 Ac,and their synergistic mechanism needs to be further explored.3.In the test of the ability of the synergistic protein PxALP or PxCAD1 to hydrolyze the midgut protease,it was found that at a concentration of 50 mg/m L,PxALP significantly increased the activation of Cry1 Ac protoxin by the midgut extract at 0.5 h,and with time Over time,its Cry1 Ac protoxin activation level no longer increases significantly.It shows that PxALP accelerates the activation rate of Cry1 Ac protoxin.4.After feeding PxALP or a mixture of PxCAD1 and Cry1 Ac,compared with feeding only Cry1 Ac,the expression of Px PGRP1/2/3 was significantly increased,and the expression of Px PGRP2 was the highest,followed by Px PGRP1 and Px PGRP3.It shows that the synergistic effect of PxALP or PxCAD1 can cause a significant response of the immune system of P.xylostella.This may be related to the synergistic mechanism of PxALP or PxCAD1.To sum up,in this experiment,there are big differences in the types of bacteria that can be cultivated in the intestine of P.xylostella,and the physiological and biochemical functions of the bacteria in the field population,Cry1 Ac resistant strains and sensitive strains,and the bacteria extracted from the resistant strains are found Growth is affected by Cry1 Ac,which may indicate that there is a relationship between the resistance of P.xylostella to Bt and the types of intestinal bacteria.The synergistic protein PxALP or PxCAD1 has no significant effect on the types of cultivable bacteria in the intestine of P.xylostella,and has no significant effect on the binding ability of BBMV and Cry1 Ac activated toxin,while PxALP or PxCAD1 has a certain effect on the activation of Cry1 Ac protoxin by the midgut protease.In addition,the synergistic protein PxALP or PxCAD1 has an impact on the immune system of P.xylostella.The results of this study provide some new evidence for exploring the relationship between the resistance of diamondback moth to Bt and its intestinal bacterial species and physiological and biochemical functions,and provide some ideas for the development and utilization of the synergistic proteins PxALP and PxCAD1.