Verticillium longisporum infection induces organ-specific glucosinolate degradation in Arabidopsis thaliana.

Katja Witzel,Monika Schreiner,Rebecca Klopsch,Rita Grosch,Silke Ruppel,Franziska S Hanschen

doi:10.3389/fpls.2015.00508

Katja Witzel, Monika Schreiner + Show 4 more

Open Access

https://doi.org/10.3389/fpls.2015.00508

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Abstract

The species Verticillium represents a group of highly destructive fungal pathogens, responsible for vascular wilt in a number of crops. The host response to infection by Verticillium longisporum at the level of secondary plant metabolites has not been well explored. Natural variation in the glucosinolate (GLS) composition of four Arabidopsis thaliana accessions was characterized: the accessions Bur-0 and Hi-0 accumulated alkenyl GLS, while 3-hydroxypropyl GLS predominated in Kn-0 and Ler-0. With respect to GLS degradation products, Hi-0 and Kn-0 generated mainly isothiocyanates, whereas Bur-0 released epithionitriles and Ler-0 nitriles. An analysis of the effect on the composition of both GLS and its breakdown products in the leaf and root following the plants’ exposure to V. longisporum revealed a number of organ- and accession-specific alterations. In the less disease susceptible accessions Bur-0 and Ler-0, colonization depressed the accumulation of GLS in the rosette leaves but accentuated it in the roots. In contrast, in the root, the level of GLS breakdown products in three of the four accessions fell, suggestive of their conjugation or binding to a fungal target molecule(s). The plant-pathogen interaction influenced both the organ- and accession-specific formation of GLS degradation products.

Highlights

A characteristic feature of Brassicaceous plants is the presence of glucosinolates (GLS), a group of sulfur-containing secondary metabolites which contribute to the plant’s defense against a range of biotic stresses (Agerbirk et al, 2009; Textor and Gershenzon, 2009)
Variation among the Four A. thaliana Accessions for Disease Susceptibility The impact of the V. longisporum inoculation was stronger on the roots than on the leaf (Figure 1)
A full tabulation of the various GLS compounds identified is presented as Supplementary Table S1; this includes those compounds which were inconsistently present and not analyzed further

Summary

Introduction

A characteristic feature of Brassicaceous plants is the presence of glucosinolates (GLS), a group of sulfur-containing secondary metabolites which contribute to the plant’s defense against a range of biotic stresses (Agerbirk et al, 2009; Textor and Gershenzon, 2009). While GLS content is typically up-regulated by pathogen or pest attack, other forms of stress, notably UVB radiation (Mewis et al, 2012b) and drought (Mewis et al, 2012a) can induce their accumulation. GLS are found in the vacuole; when the cell is disrupted, they interact with myrosinase to form either ITCs or nitriles. If the epithiospecifier protein (ESP) is present, the degradation process of alkenyl GLS generates an epithionitrile. The ESP protein has been identified to favor the formation of nitriles from other (non-alkenyl) GLS (Wittstock and Burow, 2010; Kissen et al, 2012). Nitriles and epithionitriles are generally less bioactive (Shofran et al, 1998; Matusheski and Jeffery, 2001; Wittstock et al, 2003)

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