Perception of unrelated microbe-associated molecular patterns triggers conserved yet variable physiological and transcriptional changes in Brassica rapa ssp. pekinensis

Wanhui Kim,Maxim Prokchorchik,Seulgi Kim,Hyelim Jeon,Yonghua Tian,Cécile Segonzac

doi:10.1038/s41438-020-00410-0

Abstract

Pattern-triggered immunity (PTI) includes the different transcriptional and physiological responses that enable plants to ward off microbial invasion. Surface-localized pattern-recognition receptors (PRRs) recognize conserved microbe-associated molecular patterns (MAMPs) and initiate a branched signaling cascade that culminate in an effective restriction of pathogen growth. In the model species Arabidopsis thaliana, early PTI events triggered by different PRRs are broadly conserved although their nature or intensity is dependent on the origin and features of the detected MAMP. In order to provide a functional basis for disease resistance in leafy vegetable crops, we surveyed the conservation of PTI events in Brassica rapa ssp. pekinensis. We identified the PRR homologs present in B. rapa genome and found that only one of the two copies of the bacterial Elongation factor-Tu receptor (EFR) might function. We also characterized the extent and unexpected specificity of the transcriptional changes occurring when B. rapa seedlings are treated with two unrelated MAMPs, the bacterial flagellin flg22 peptide and the fungal cell wall component chitin. Finally, using a MAMP-induced protection assay, we could show that bacterial and fungal MAMPs elicit a robust immunity in B. rapa, despite significant differences in the kinetic and amplitude of the early signaling events. Our data support the relevance of PTI for crop protection and highlight specific functional target for disease resistance breeding in Brassica crops.

Highlights

Perception of non-self or damaged-self is essential for plants to adjust to environmental changes and is of particular importance to ward off pathogen invasion
Prior to test the range of Microbeassociated molecular patterns (MAMPs) detected by B. rapa, we surveyed its genome for the presence of patternrecognition receptor (PRR) gene homologs (Table 1, Fig. S1)
The rapid production of reactive oxygen species (ROS) and the transient up-regulation of BraNLH10 in Norang seedlings treated with LPS, PGN, elf[18], chitin and flg[22] indicate that functional PRRs could detect different MAMPs in B. rapa leaf

Summary

Introduction

Perception of non-self or damaged-self is essential for plants to adjust to environmental changes and is of particular importance to ward off pathogen invasion. Plants have evolved two major sets of receptors that recognize the presence of microbes and activate defense mechanisms that efficiently restrict pathogen growth[1]. Microbeassociated molecular patterns (MAMPs) are conserved features essential for microbial survival. MAMPs may bind to the extracellular domain of the plant pattern-recognition receptors (PRRs), leading to activation of conserved sets of defense responses including a wide transcriptional reprograming, hormonal changes, reinforcement of the plant cell wall and production of antimicrobial compounds[3]. Plants lacking PRRs are generally more susceptible to pathogens, highlighting the contribution of the pattern-triggered immunity (PTI) to plant disease resistance[4]

Methods

Results

Conclusion