Study On The Function Of JH Pathway In The "Tree Top Disease" Of Lymantria Dispar

“Tree top disease”,as a classic virus inducing host to climb and hang upside-down,has attracted wide attention.In recent years,relevant studies have explained the possible causes of this phenomenon mainly from the perspective of virus genes and environment,while the influence of host hormone and signaling pathway changes on climbing behavior after infection with baculovirus remains unclear.In this study,Lymantria dispar was selected as the research object to explore the molecular mechanism of climbing behavior in treetop disease,mainly from the juvenile hormone pathway genes and the changes of microbial community in Lymantria dispar.The research results mainly include the following four aspects.1.Interference with genes related to juvenile hormone pathway affects the climbing behavior of infected larvae: In the juvenile hormone pathway,juvenile hormone acid methyltransferase gene(JHAMT),methoprene-tolerant gene(Met)and target of rapamycin gene(TOR)were interfered by dsRNA feeding.The results showed that silenced of JHAMT,Met,and TOR genes resulted in a decrease in the height of death of L.dispar larvae infected with LdMNPV,suggested that the JHAMT,Met and TOR genes was involved in climbing behavior in “Tree top disease”.2.TOR positively regulates the juvenile hormone pathway: Quantitative experiments showed that the down-regulation of TOR gene would lead to down-regulation of both JHAMT and Met genes.Meanwhile,the downregulation of JHAMT and Met genes could also lead to the up-regulation of TOR gene expression.These results indicated that the TOR gene had a positive regulatory effect on the juvenile hormone pathway of L.dispar larvae.3.The microflora of infected larvae changed significantly: LdMNPV infection can significantly change the microbial community and structure in gypsy moth.The relative abundance of Gram-negative and Gram-positive bacteria communities could regulate the expression of the Toll pathway and Imd pathway,and activate the NF-κβ pathway to release antimicrobial peptides.These results indicated that microbial changes affect insect immunity in L.dispar larvae.4.The changes of microflora in infected larvae affect the juvenile hormone pathway:Antibiotic feeding could eliminate part of the microbial community in L.dispar larvae.In antibiotic treatment groups,the expression of juvenile hormone receptor gene Met and rapamycin target protein gene TOR were different from the normal groups.These results indicated that changes in microbial community in L.dispar larvae could affect the expression of genes related to juvenile hormone pathway.But there was little effect on climbing behavior in “Tree top disease”.In conclusion,the effect of juvenile hormone pathway L.dispar larvae "treetop disease".Interference of juvenile hormone pathway related genes JHAMT,Met and TOR resulted in a significant decrease in the height of L.dispar larvae after infection with LdMNPV.TOR gene,the target protein of rapamycin,positively regulates the juvenile hormone pathway.The altered of the microbial community relatively abundance in L.dispar larvae could affect the host juvenile hormone pathway and the immune pathway,but has little effect on the climbing behavior in "treetop disease".The reason needs further study.These results provide a new scientific basis for clarifying the mechanism of L.dispar “treetop disease”.