Multi-Omics Revealed Molecular Mechanisms Underlying Guard Cell Systemic Acquired Resistance.

Lisa David,Sixue Chen,Dan Zhu,Jianing Kang,Daniel Dufresne

doi:10.3390/ijms22010191

Abstract

Systemic Acquired Resistance (SAR) improves immunity of plant systemic tissue after local exposure to a pathogen. Guard cells that form stomatal pores on leaf surfaces recognize bacterial pathogens via pattern recognition receptors, such as Flagellin Sensitive 2 (FLS2). However, how SAR affects stomatal immunity is not known. In this study, we aim to reveal molecular mechanisms underlying the guard cell response to SAR using multi-omics of proteins, metabolites and lipids. Arabidopsis plants previously exposed to pathogenic bacteria Pseudomonas syringae pv. tomato DC3000 (Pst) exhibit an altered stomatal response compared to control plants when they are later exposed to the bacteria. Reduced stomatal apertures of SAR primed plants lead to decreased number of bacteria in leaves. Multi-omics has revealed molecular components of SAR response specific to guard cells functions, including potential roles of reactive oxygen species (ROS) and fatty acid signaling. Our results show an increase in palmitic acid and its derivative in the primed guard cells. Palmitic acid may play a role as an activator of FLS2, which initiates stomatal immune response. Improved understanding of how SAR signals affect stomatal immunity can aid biotechnology and marker-based breeding of crops for enhanced disease resistance.

Highlights

Systemic acquired resistance (SAR) is an inducible defense mechanism that is activated throughout the plant after a localized pathogen infection
Through multi-omics of proteins, metabolites, and lipids from guard cells of uninoculated leaves of primed Arabidopsis plants, we found that reactive oxygen species (ROS) and fatty acids (FAs) signals are activated in the primed guard cells, and we identified proteins, lipids, and metabolites with previously unknown functions, which may be involved in the systemic stomatal immune response
There was no significant difference in the stomatal aperture from the primed leaves taken at 0, 1, and 3 h after Pst exposure (Figure 1B)

Summary

Introduction

Systemic acquired resistance (SAR) is an inducible defense mechanism that is activated throughout the plant after a localized pathogen infection. It confers resistance to a broad range of pathogens in systemic tissues. SAR occurs when the plant delivers mobile signals from the primary site of infection to the remote, uninfected tissues [1,2,3,4,5]. Upon receiving the mobile immune signals, the remote tissue mounts a defense against the pathogens in a robust manner. This mechanism is called “priming” and those uninfected remote leaves are said to be “primed” for pathogen response. SAR priming endows the plant with a broadspectrum resistance, including to pathogens that cause cell death and tissue necrosis [6,7,8]

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