Study On The Mechanism Of The Effect Of Feeding On The Anti-fungal Infection Ability Of C. Taiwanensis

Coptotermes formosanus shriaki,one of the world's five most recognized pests,has evolved an unique defense mechanism to resist the infection of pathogens and changes in the environment due to the particularity of life history.Defense mechanisms of termites include group defense strategies and individual defense mechanisms.Many factors,such as temperature,genetics hormones and nutrients all have certain effects on the immunity of termites.However,the relationship between nutrition and immunity of termites is not clear.In this study,we used bioassays,histological analysis and q-PCR to compared the effects of different feedings on the antifungal immunity of Coptotermes formosanus.Our study can provide a theoretical basis for exploring the relationship between termite feeding and immune defense.The results of this study are as follows:1.Effect of different feeding treatments on fungal resistance of termiteAfter feeding the filter paper supplemented with 0.5%lignin,5%sucrose,0.5%peptone and equal volume of distilled water for 15 d,there was no significant difference in feeding amount among the 4 groups.However,the feeding amount of the lignin group was significantly greater than other groups.After infection with high concentrations of Beauveria bassiana and Metarhizium anisopliae for 15 d,the grooming of the paired termites was observed.Our analysis suggests that allogrooming duration of tennites was significantly longer than that of control group and B.bassiana group after infection with 3×107 spores/mL.However,there was no significant difference between B.bassiana groups and control groups in grooming duration and allogrooming frequency.We found that there was no significant difference in allogrooming duration and frequency among the termites infected by the same fungus in different feeding groups.There was no significant difference in mortality among the four groups within 40 h?64 h after infection with B.bassiana,but the mortality of termites in the peptone feeding group was significantly lower than the control group at 64 h post infection.There was no significant difference in mortality among the four feeding groups at 9 d post infection with B.bassiana,but the mortality of the lignin feeding group was significantly higher than that in the other 3 groups at 12 d?15 d post infection.After infection with 3.bassiana and for 3 d?4 d,the mortality of individual termites can reach 100%.While the multiple termites are infected with B.bassiana for more than 20 d,the mortality rate would reach above 80%,and the KT50 was 11 d?18 d.The results indicate group defense of termites are significantly higher than that of individuals.2.Changes in immune gene relative transcription amount of termites with different feeding treatments during the resistance to infectionAfter feeding the filter paper supplemented with 0.5%lignin,5%sucrose,0.5%peptone and equal volume of distilled water for 15 d,individual termites of 4 feeding groups were infected with 3×106 spores/mL B.bassiana,and the relative expression levels two immune genes in termites were analyzed by qPCR.We found that lysozyme relative expression level decreased at 16 h post infection among 4 groups.The lys relative expression of lignin feeding group increased significantly at 48 h post infection,while there were no significant differences between the other 3 groups and the control group.The transferrin relative expression of distilled water group increased in the pre-infection period,but the other 3 groups did not increase.Furthermore,the relative expression of tsf decreased among the 4 feeding groups at 48 h post infection.In conclusion,food had no significant effect on the expression of lys and tsf in termites infected with fungus at 16 h and 48 h.3.Histological changes of termites with different feeding processes during the infection with fungusFor individual infection experiments,it was observed that there were encapsulations in the termites to resistant spore infection.Histological observations revealed that a series of changes occurred in the tissues of termites at 48 h post infection,including the disintegration of body wall cells,vacuole-like structures between cells,disintegration of bowel wall and formation of encapsulation.There was no significant differences in the histological changes of termites among different feeding groups.When multiple termites infected with B.bassiana,the spores of termites in the digestive tract can be observed at 24 h post infection,indicating that the grooming of the group can remove some spores to the surface of the termites.A large number of hyphae were grown in the termite bodies after 24 h of death.There are numerous hyphae between the anus and cephalothorax of termites.