A-to-I RNA editing in bacteria increases pathogenicity and tolerance to oxidative stress

Abstract

Adenosine-to-inosine (A-to-I) RNA editing is an important posttranscriptional event in eukaryotes; however, many features remain largely unexplored in prokaryotes. This study focuses on a serine-to-proline recoding event (S128P) that originated in the mRNA of fliC , which encodes a flagellar filament protein; the editing event was observed in RNA-seq samples exposed to oxidative stress. Using Sanger sequencing, we show that the S128P editing event is induced by H 2 O 2 . To investigate the in vivo interaction between RNAs and TadA, which is the principal enzyme for A-to-I editing, genome-wide RNA immunoprecipitation–coupled high-throughput sequencing (iRIP-Seq) analysis was performed using HA-tagged TadA from Xanthomonas oryzae pv. oryzicola . We found that TadA can bind to the mRNA of fliC and the binding motif is identical to that previously reported by Bar-Yaacov and colleagues. This editing event increased motility and enhanced tolerance to oxidative stress due to changes in flagellar filament structure, which was modelled in 3D and measured by TEM. The change in filament structure due to the S128P mutant increased biofilm formation, which was measured by the 3D laser scanning confocal microscopy. RNA-seq revealed that a gene cluster that contributes to siderophore biosynthesis and Fe 3+ uptake was upregulated in S128P compared with WT. Based on intracellular levels of reactive oxygen species and an oxidative stress survival assay, we found that this gene cluster can contribute to the reduction of the Fenton reaction and increases biofilm formation and bacterial virulence. This oxidative stress response was also confirmed in Pseudomonas putida . Overall, our work demonstrates that A-to-I RNA editing plays a role in bacterial pathogenicity and adaptation to oxidative stress.

Oxidative Stress in Bacteria and the Central Dogma of Molecular Biology

“…A recent report linked a specific A-to-I editing event on the mRNA of the flagellar filament protein fliC to an increased virulence in the bacterial plant pathogen Xanthomonas oryzae pv. oryzicola ( Xoc ) ( Nie et al, 2020 ). Plants often generate ROS as a defensive reaction to either directly kill invading pathogens or, more importantly, work as signaling molecules for gene expression activation in the context of pathogen defense ( Torres et al, 2006 ; Paiva and Bozza, 2014 ).…”

“…The authors identified a serine to proline mutation (S128P) in FliC after exposing the bacteria to H 2 O 2 . The S128P editing event can potentially change filament structure and enhance biofilm formation, leading to an increased oxidative stress tolerance ( Nie et al, 2020 ).…”

A key antisense sRNA modulates the oxidative stress response and virulence in Xanthomonas oryzae pv. oryzicola

“…To deal with oxidative stress, bacterial pathogens often deploy enzymes that either tolerate or scavenge ROS. We recently demonstrated that adenosine-to-inosine (A-to-I) RNA editing in Xoc increased tolerance to H 2 0 2 [ 20 ]. A-to-I editing in the target fliC caused structural changes in flagella that increased biofilm formation and ultimately improved ROS tolerance [ 20 ].…”

“…We recently demonstrated that adenosine-to-inosine (A-to-I) RNA editing in Xoc increased tolerance to H 2 0 2 [ 20 ]. A-to-I editing in the target fliC caused structural changes in flagella that increased biofilm formation and ultimately improved ROS tolerance [ 20 ]. A number of studies have shown that sRNAs can also regulate tolerance to oxidative stress in prokaryotes [ 22 ].…”

“…Our lab is interested in the role of post-transcriptional RNA regulation and editing in Xoc , especially with respect to pathogenicity, motility, biofilm formation and adaptation to oxidative stress [ 20 ]. This study focuses on sRNA Xonc3711, which is the Xoc homolog of sRNA-Xoo1; as mentioned above, sRNA-Xoo1 was responsive to oxidative stress [ 19 ].…”