Drosophila lncRNA-NANPI enhances Toll signaling pathway by interacting with Dif/Dorsal to facilitate transcription of antibacterial peptides

LncRNAs have important regulatory functions but their roles in Drosophila innate immunity are poorly understood. The Drosophila Toll signaling pathway responds to Gram-positive bacterial infection and is highly conserved with mammalian TLR signaling. Recent studies focused mainly on Toll signaling pathway regulation by protein-coding genes. In the present study, we found that lncRNA-CR33942 was upregulated after Micrococcus luteus infection. Gain-of-function and loss-of-function assays disclosed that lncRNA-CR33942 regulates the Toll signaling pathway and affects Drosophila survival. RNA-seq of infected CR33942-overexpressing flies was performed to explore the CR33942 mechanism. About 70% of all upregulated core enrichment genes in the Toll signaling pathway were antibacterial peptides and PGRPs transcribed by Dif/Dorsal. We also demonstrated CR33942 interactions with Dif/Dorsal and revealed that they induce antibacterial peptides. Hence, we renamed CR33942 as lncRNA-NANPI (NF-?B-associated non-coding RNA promotional immunology). The present study identified the novel Toll signaling pathway regulator NANPI, elucidated its mode of action, clarified the function of lncRNA, and expanded our understanding of the Toll signaling pathway. Overall design: the infected M. luteus male adult CR33942-overexpressing and control flies were collected at 12 h post-infection for subsequently RNA-seq