lncRNA-CR11538 functions as a decoy of Dif/Dorsal to negatively regulate Drosophila Toll immune responses

The maintenance of innate immune homeostasis is critical for animal survival to combat pathogens. Although many positive or negative protein factors have been identified, little is known about the long non-coding RNA that regulates the Toll pathway. Herein, we have discovered a novel lncRNA-CR11538 highly activated during the Drosophila response to gram+ bacterial infection. The transient overexpression of CR11538 inhibited the expression of antimicrobial peptides (Drosomycin and Metchnikowin) in vivo to suppress Toll signaling pathway. Remarkably, core enrichment genes based on RNAseq, subcellular localization and RIP suggest that CR11538 can interact with the transcription factor Dif/Dorsal in nucleus. ChIP-qPCR and dual luciferase report experiments show that CR11538 can sequester Dif/Dorsal away from the promoter thus suppressing the transcription of antimicrobial peptides. In summary, we discovered a novel lncRNA-CR11538 that negatively regulate the Drosophila Toll pathway. It broadens our understanding of the regulatory mechanism of Toll pathway involving lncRNA and provides insights for the research on innate immune system of insects and mammals. Overall design: the infected M. luteus male adult CR11538-overexpressing and control flies were collected at 12 h post-infection for subsequently RNA-seq