Relish-mediated lncRNA-CR33942 facilitates Drosophila Imd immune responses and promotes antimicrobial peptide expression via interacting with Relish

Long noncoding RNAs (lncRNAs), as a class of emerging regulators, play crucial role in regulating the strength and duration of innate immunity. However, little is known about how these Drosophila Imd immunity-related lncRNAs are regulated. Herein, we firstly revealed that overexpression of lncRNA-CR33942 could strengthen the expression of Imd pathway antimicrobial peptides Diptericin (Dpt) and Attacin-A (AttA) after infection, and vice versa. Secondly, RNA-seq analysis of post-infected lncRNA-CR33942-overexpressing flies further confirmed that lncRNA-CR33942 positively regulates the Drosophila Imd pathway. Mechanistically, we indicated that lncRNA-CR33942 interacts with NF-κB transcription factor Relish to promote its binding to Dpt and AttA promoters, thereby facilitating Dpt and AttA expression. Interestingly, we found that Relish can also directly promote lncRNA-CR33942 transcription by binding to its promoter. Finally, rescue experiments and dynamic expression profiling post-infection demonstrated the vital role of the Relish/lncRNA-CR33942/AMPs regulatory axis in enhancing inadequate Imd immune responses and maintaining immune homeostasis. Taken together, our study not only elucidates a novel mechanism about lncRNA in Drosophila Imd immune regulation, but also has important guiding significance for elucidating the complex regulatory mechanism of animal innate immune response. the CR33942-overexpressing and control male adult flies were collected at 12 h after E. coli infection for subsequently RNA-seq