AUTHOR=Wang Jianan , Liu Jun , Zhao Yuqiang , Sun Minghui , Yu Guixu , Fan Jiaqin , Tian Yanli , Hu Baishi 

TITLE=OxyR contributes to virulence of Acidovorax citrulli by regulating anti-oxidative stress and expression of flagellin FliC and type IV pili PilA

JOURNAL=Frontiers in Microbiology

VOLUME=13

YEAR=2022

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2022.977281

DOI=10.3389/fmicb.2022.977281

ISSN=1664-302X

ABSTRACT=<p>In many bacteria, OxyR acts as a transcriptional regulator that facilitates infection <italic>via</italic> degrading hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) generated by the host defense response. Previous studies showed that OxyR also plays an important role in regulating biofilm formation, cell motility, pili relate-genes expression, and surface polysaccharide production. However, the role of OxyR has not been determined in <italic>Acidovorax citrulli</italic> strain xjl12. In the current study, the qRT-PCR and western blot assays revealed that the expression level of <italic>oxyR</italic> was significantly induced by H<sub>2</sub>O<sub>2</sub>. The <italic>oxyR</italic> deletion mutant of <italic>A. citrulli</italic> was significantly impaired bacterial tolerance to oxidative stress and reduced catalase (CAT) activity. In addition, <italic>oxyR</italic> mutant resulted in reduced swimming motility, twitching motility, biofilm formation, virulence, and bacterial growth in <italic>planta</italic> by significantly affecting flagellin and type IV pili-related gene (<italic>fliC</italic> and <italic>pilA</italic>) expression. The qRT-PCR assays and western blot revealed that OxyR positively regulated the expression of <italic>fliC</italic> and <italic>pilA.</italic> Furthermore, bacterial one-hybrid assay demonstrated that OxyR directly affected <italic>pilA</italic> and <italic>fliC</italic> promoter. Through bacterial two-hybrid assay, it was found that OxyR can directly interact with PilA and FliC. These results suggest that OxyR plays a major role in the regulating of a variety of virulence traits, and provide a foundation for future research on the global effects of OxyR in <italic>A. citrulli</italic>.</p>