Bacillus velezensis tolerance to the induced oxidative stress in root
colonization contributed by the two-component regulatory system sensor
ResE
Abstract
Efficient root colonization of the plant growth-promoting rhizobacteria
is critical for their plant-beneficial functions. However, their
strategy to overcome plant immunity in root colonization is not well
understood. In particular, how Bacillus strains overcome the
plant-derived ROS, which functions as the first barrier of plant
defense, is not clear. In the present study, we found that the homologue
of flg22 in B. velezensis SQR9 (flg22SQR9) has 78.95% identity to the
typical flg22 (flg22P.s.) and could induce significant oxidative burst
in cucumber and Arabidopsis. In contrast to pathogenic or beneficial
Pseudomonas, living B. velezensis SQR9 induced an oxidative burst in
plant. We further found that B. velezensis SQR9 could tolerate higher
H2O2 than Pseudomonas syringae pv. tomato (Pst) DC3000, the pathogen
that harbored the typical flg22, and possesses the ability to suppress
the flg22-induced oxidative burst, indicating that B. velezensis SQR9
may exploit a more efficient ROS tolerance system than DC3000. Further
experimentation with mutagenesis of bacteria and Arabidopsis showed that
the two-component regulatory system sensor ResE in B. velezensis SQR9
was involved in tolerance of plant-derived oxidative stress, thus
contributing to root colonization. This study supports the further
investigation of interaction between beneficial rhizobacteria and plant
immunity.