1-Methyltryptophan Modifies Apoplast Content in Tomato Plants Improving Resistance Against Pseudomonas syringae.

Loredana Scalschi,Begonya Vicedo,Mercedes Valcárcel,Ana I González-Hernández,Gemma Camañes,Eugenio Llorens,Pilar García-Agustín,Jordi Gamir

doi:10.3389/fmicb.2018.02056

Abstract

Plants can produce numerous natural products, many of which have been shown to confer protection against microbial attack. In this way, we identified 1-methyltryptophan (1-MT), a natural compound produced by tomato plants in response to Pseudomonas syringae attack, whose application by soil drench provided protection against this pathogen. In the present work, we have studied the mechanisms underlying this protection. The results demonstrated that 1-MT can be considered a new activator of plant defense responses that acts by inhibiting the stomatal opening produced by coronatine (COR) and could thereby, prevent bacteria entering the mesophyll. Besides, 1-MT acts by blocking the jasmonic acid (JA) pathway that, could avoid manipulation of the salicylic acid (SA) pathway by the bacterium, and thus hinder its growth. Although the concentration of 1-MT reached in the plant did not show antimicrobial effects, we cannot rule out a role for 1-MT acting alone because it affects the expression of the fliC gene that is involved in synthesis of the flagellum. These changes would result in reduced bacterium motility and, therefore, infective capacity. The results highlight the effect of a tryptophan derivative on induced resistance in plants.

Highlights

Plants have developed a variety of chemical and physical basal defense mechanisms to cope with environmental changes and pathogenic invasions
The pathosystem Pseudomonas syringae vs. tomato is a widely used model to study the plant–pathogen interaction: firstly given its genetic tractability and pathogenicity, Pseudomonas syringae pv. tomato DC3000 is an appropriate strain used to investigate plant– microbe interactions (Cuppels, 1986; Elizabeth and Bender, 2007; Uppalapati et al, 2008); secondly, tomato is an economically important plant and its study could be extended to other species closely related to it that are important for agriculture
We have previously reported that 1-MT protects tomato plants against P. syringae and B. cinerea (Camañes et al, 2015)

Summary

Introduction

Plants have developed a variety of chemical and physical basal defense mechanisms to cope with environmental changes and pathogenic invasions. The ability to detect and activate a defense response against potentially pathogenic microorganisms is important for stopping disease progression. The activation of these defense systems is linked to the recognition of pathogen-associated molecular patterns (PAMPs), such as lipopolysaccharides and flagellin in Gram-negative bacteria, or chitin and ergosterol in higher fungi (Nürnberger et al, 2004). 1-MT Modulates Resistance Against Pst. The plant–pathogen interaction is a system that depends on the lifestyle of the microorganism and plant species. Tomato DC3000 is an appropriate strain used to investigate plant– microbe interactions (Cuppels, 1986; Elizabeth and Bender, 2007; Uppalapati et al, 2008); secondly, tomato is an economically important plant and its study could be extended to other species closely related to it that are important for agriculture The pathosystem Pseudomonas syringae vs. tomato is a widely used model to study the plant–pathogen interaction: firstly given its genetic tractability and pathogenicity, Pseudomonas syringae pv. tomato DC3000 is an appropriate strain used to investigate plant– microbe interactions (Cuppels, 1986; Elizabeth and Bender, 2007; Uppalapati et al, 2008); secondly, tomato is an economically important plant and its study could be extended to other species closely related to it that are important for agriculture

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