Objective  Listeria innocua is a non-pathogenic bacterium from the Listeria genus, which harbors the virulence factors evolved from the same ancestor with the pathogenic bacterium L. monocytogenes. This study aims to investigate the transcriptional variations of host cells after L. innocuainfection, and provide a basis for host regulation and prevention of damage from L. monocytogenes.

Method  We used L. innocua to infect Drosophila melanogaster S2 cells and analyzed the change of gene expression in Drosophila S2 cells by transcriptome sequencing. The differentially expressed genes in Drosophila S2 cells infected by L. innocua was verified by qPCR.

Result  The Toll/Imd signaling pathways were significantly upregulated in Drosophila S2 cells after L. innocua infection for three hours, while the phagosome and Vibrio cholerae infection signaling pathways were significantly downregulated. The antimicrobial peptide genes including DmDef (DmDefensin), DmDro (DmDrosomycin), DmDpt A (DmDptericin A), DmDpt B (DmDptericin B), DmMtk (DmMetchnikowin), DmCec A2 (DmCecropin A2), DmAtt A (DmAttacin A), DmAtt B (DmAttacin B), DmAtt D (DmAttacin D), and DmCec B (DmCecropin B) were significantly induced after L. innocua infection. Among them, the most upregulated gene was DmDef with 9.805 fold change. The qPCR verification results showed that the expressions of DmMtk, DmAtt A, DmDro and DmDef genes were upregulated by 8.180, 7.533, 7.204 and 4.569 fold.

Conclusion  After L. innocua infection, the genes with the most significant change in Drosophila S2 cells are antimicrobial peptide genes. This study offers a comprehensive investigation of gene expression changes in Drosophila S2 cells after L. innocua infection, and provide a reference for revealing the response of host cells evoked by non-pathogenic bacteria as well as interaction studies between bacterial pathogens and hosts.