The Intruding Wolbachia Strain from the Moth Fails to Establish Itself in the Fruit Fly Due to Immune and Exclusion Reactions

Wolbachia is capable of regulating host reproduction, and thus of great significance in preventing the spread of insect-borne diseases and controlling pest insects. The fruit fly Drosophila melanogaster is an excellent model insect for understanding Wolbachia -host interactions. Here we artificially transferred the w Ccep strain from the rice moth Corcyra cephalonica into D. melanogaster by microinjection. Crossing experiments indicated that w Ccep could induce a high level of CI in the phylogenetically distant host D. melanogaster and imposed no negative fitness costs on host development and fecundity. Based on quantitative analysis, the titres of w Ccep and the native w Mel strain were negatively correlated, and w Ccep could only be transmitted in the novel host for several generations (G 0 to G 4 ) after transinfection. Transcriptome sequencing indicated that the invading w Ccep strain induced a significant immune- and stress-related response from the host. An association analysis between the expression of immune genes attacin -D/ edin and the titre of Wolbachia by linear regression displayed a negative correlation between them. Our study suggest that the intrusion of w Ccep elicited a robust immune response from the host and incurred a competitive exclusion from the native Wolbachia strain, which resulted in the failure of its establishment in D. melanogaster .