A Small Regulatory RNA, Rli82, Is Involved in the Motility and Pathogenicity of Listeria monocytogenes

Background: Listeria monocytogenes (LM) is a facultative intracellular pathogen that causes food-borne infections in humans and animals. To invade and multiply within host cells, LM utilizes various strategies to precisely modulate its gene expression and to adapt to the in vivo environment. Objectives: To investigate the regulatory roles of Rli82 sRNA in the motility and pathogenicity of LM EGD-e. Methods: The Rli82 gene knock-out mutant strain, LM-ΔRli82, and the complementation strain, LM-ΔRli82/Rli82, were constructed using homologous recombination technology, and their motility and virulence, respectively, were determined. Moreover, the potential target mRNA regulated by Rli82 was predicted using TargetRNA2 software, and then the interaction between the target mRNA and Rli82 was verified by the two-plasmid reporter system. Results: The results showed that the motility of LM-ΔRli82 was significantly increased at 25°C, facilitated by the production of more flagella than LM EGD-e and LM-ΔRli82/Rli82. Furthermore, LD50 in LM-ΔRli82-infected mice was significantly increased as compared to LM EGD-e and LM-ΔRli82/Rli82, suggesting that the virulence of LM was weakened when the Rli82 gene was deleted. In addition, the mRNA level of flaA was not significantly elevated, but flaA protein was significantly higher in LM-ΔRli82 than in LM EGD-e and LM-ΔRli82/Rli82, suggesting that Rli82 might modulate the translation of flaA mRNA at the post-transcriptional level. Conclusions: Taken together, our findings for the first time revealed that Rli82 sRNA might be involved in the modulation of the expression of flaA protein, thereby influencing the mobility and pathogenicity of LM.