Endophyte Bacillus subtilis evade plant defense by producing lantibiotic subtilomycin to mask self-produced flagellin

Yun Deng,Jianyi Xu,Jinshui Zheng,Yiguang Zhu,Congzhi Li,Qingdong Qi,Ming Sun,Donghai Peng,Hanqiao Chen,Lifang Ruan,Yuanyuan Xu

doi:10.1038/s42003-019-0614-0

Abstract

Microbes can enter into healthy plants as endophytes and confer beneficial functions. The entry of commensal microbes into plants involves penetrating plant defense. Most mechanisms about overcoming plant defense are focused on adapted pathogens, while the mechanism involved in beneficial endophyte evades plant defense to achieve harmonious commensalism is unclear. Here, we discover a mechanism that an endophyte bacterium Bacillus subtilis BSn5 reduce to stimulate the plant defensive response by producing lantibiotic subtilomycin to bind self-produced flagellin. Subtilomycin bind with flagellin and affect flg22-induced plant defense, by which means promotes the endophytic colonization in A. thaliana. Subtilomycin also promotes the BSn5 colonization in a distinct plant, Amorphophallus konjac, where the BSn5 was isolated. Our investigation shows more independent subtilomycin/-like producers are isolated from distinct plants. Our work unveils a common strategy that is used for bacterial endophytic colonization.

Highlights

Microbes can enter into healthy plants as endophytes and confer beneficial functions
We inferred that the isolated antibacterial protein, Apn[5], was a complex of flagellin and lantibiotic subtilomycin
The collected elution fragments were transferred to SDS–PAGE assay and inhibition activity assay to relatively quantify flagellin and subtilomycin, respectively

Summary

Introduction

Microbes can enter into healthy plants as endophytes and confer beneficial functions. The conserved 22 amino acids epitope, flg[22], in the N-terminal region of the flagellin from pathogen bacteria elicits the defensive response after the recognition by the receptor FLS2 in Arabidopsis thaliana[15,16]. To avoid this defensive response, adapted pathogens evolved various effectors to attenuate the pattern-triggered response. A few cases mentioned that beneficial microbes downregulate the expression of the MAMPs19–21, produce the MAMPs with low-elicit ability[22], or produce some required genes[23] to reduce the stimulation of plant defensive response. The mechanism that commensal endophyte bacteria used to modulate plant defense is rarely reported like the recent review stated[12]

Methods

Results

Conclusion