# Reactive oxygen species in the rhizosphere orchestrate the recruitment of beneficial bacteria

## TL;DR

This study shows that reactive oxygen species in plant roots attract helpful bacteria, which in turn boost plant growth and reduce disease symptoms.

## Contribution

ROS are shown to recruit beneficial bacteria, revealing a new role in plant-microbe interactions.

## Key findings

- rbohD mutant plants have fewer beneficial bacteria in the rhizosphere compared to wild-type plants.
- P. anguilliseptica is attracted to hydrogen peroxide and shows chemotactic behavior.
- P. anguilliseptica reduces disease symptoms caused by pathogens in a ROS-dependent manner.

## Abstract

Respiratory burst oxidase homolog D (RBOHD)-dependent reactive oxygen species (ROS) in Arabidopsis are well known to suppress pathogen colonization, but their influence on beneficial microbes remains unclear. Here, we found that the beneficial rhizobacterium Pseudomonas anguilliseptica was significantly less enriched in the rhizosphere of rbohD mutants than in that of wild-type plants. Conversely, elevated rhizosphere ROS levels, either triggered by pretreatment with pathogenic Dickeya solani bacteria or caused by mutations in ROS scavenging genes (e.g., in apx1 and cat2 mutants), promoted the rhizosphere recruitment of P. anguilliseptica. This promoting effect was abolished by catalase treatment. In situ microfluidic chemotaxis assays further revealed that P. anguilliseptica exhibits a chemotactic response to low concentrations of hydrogen peroxide ( ≤ 500 nM), accompanied by upregulated expression of chemotaxis- and motility-related genes. Notably, inoculation of P. anguilliseptica effectively suppressed D. solani-induced disease symptoms, and this protective effect was attenuated by catalase treatment. Collectively, these findings reveal a previously unrecognized role of ROS in recruitment beneficial microbiota to enhance plant growth and suppress disease symptoms.

ROS produced by RBOHD play a crucial role in shaping the rhizosphere microbiome. This study reveals that rhizosphere ROS attract the beneficial bacterium Pseudomonas anguilliseptica to the roots, thereby promoting plant growth and suppressing disease symptoms in Arabidopsis.

rbohD mutant plants exhibit lower levels of beneficial bacteria in the rhizosphere than the wild type.Elevated rhizosphere ROS levels promote the recruitment of P. anguilliseptica.P. anguilliseptica shows a chemotactic response to hydrogen peroxide.P. anguilliseptica mitigates pathogen-induced disease symptoms in a ROS-dependent manner.

rbohD mutant plants exhibit lower levels of beneficial bacteria in the rhizosphere than the wild type.

Elevated rhizosphere ROS levels promote the recruitment of P. anguilliseptica.

P. anguilliseptica shows a chemotactic response to hydrogen peroxide.

P. anguilliseptica mitigates pathogen-induced disease symptoms in a ROS-dependent manner.

In Arabidopsis, ROS produced by RBOHD not only inhibit pathogens but also recruit beneficial rhizobacteria, enhancing plant resistance to disease.