Three Hfq‐dependent small RNAs regulate flagellar motility in the fire blight pathogen Erwinia amylovora

Abstract

Erwinia amylovora, the causative agent of fire blight disease of apple and pear trees, causes disease on flowers by invading natural openings at the base of the floral cup. To reach these openings, the bacteria use flagellar motility to swim from stigma tips to the hypanthium and through nectar. We have previously shown that the Hfq-dependent sRNAs ArcZ, OmrAB and RmaA regulate swimming motility in E. amylovora. Here, we tested these three sRNAs to determine at what regulatory level they exert their effects and to what extent they can complement each other. We found that ArcZ and OmrAB repress the flagellar master regulator flhD post-transcriptionally. We also found that ArcZ and RmaA positively regulate flhD at the transcriptional level. The role of ArcZ as an activator of flagellar motility appears to be unique to E. amylovora and may have recently evolved. Our results suggest that the Hfq-dependent sRNAs ArcZ, OmrAB and RmaA play an integral role in regulation of flagellar motility by acting primarily on the master regulator, FlhD, but also through additional factors.

The Leucine-Responsive Regulatory Protein Lrp Participates in Virulence Regulation Downstream of Small RNA ArcZ in Erwinia amylovora

“…Because deletion of arcZ reduced flhDC mRNA abundance in E. amylovora Ea1189 (31), we hypothesized that loss of lrp acts as a suppressor mutation of Δ arcZ by restoring flhDC transcript levels. To test this hypothesis, we conducted quantitative real-time PCR analyses to quantify transcript levels in the Δ lrp mutants.…”

“…amylovora, as ArcZ acts as a negative regulator of flagellar motility in other Enterobacteriaceae (32) but is an activator of flagellar motility by transcriptionally activating flhDC in E. amylovora (31). Although we have demonstrated that ArcZ posttranscriptionally regulates lrp in E.…”

“…In contrast, ArcZ is an activator of flagellar motility in E. amylovora (33, 34), and we recently reported that ArcZ positively affects the transcription of flhDC (31). We hypothesized that an additional factor affecting flhDC transcriptionally must be regulated by ArcZ in E.…”

“…In Escherichia coli, the sRNAs ArcZ, McaS, OmrA, OmrB, and OxyS all regulate flhDC posttranscriptionally (29, 30), and in E. amylovora, the sRNAs ArcZ and OmrAB regulate flhDC posttranscriptionally (31).…”

Small RNAs as Fundamental Players in the Transference of Information During Bacterial Infectious Diseases

“…Given that motility is related with flagella, a potential target of regulation mediated by sRNAs is the dual system composed by the proteins FlhD and FlhC regulating the expression of the rest of the genes in the flagellar regulon (Liu and Matsumura, 1994;Frye et al, 2006). Schachterle et al (2019) researched the involvement of ArcZ, OmrAB, and RmaA in flagellar regulation. First, they found reduced expression levels for regulatory and flagellar structural genes in lack-of-function mutants ( arcZ, hfq, omrAB, and rmaA) in comparison with the WT.…”