Metabolite Profiling of Arabidopsis Inoculated with Alternaria brassicicola Reveals That Ascorbate Reduces Disease Severity

Abstract

The interaction between the pathogenic ascomycete Alternaria brassicicola and Arabidopsis was investigated by metabolite profiling. The effect of A. brassicicola challenge on metabolite levels was substantial, with nearly 50% of detected compounds undergoing significant changes. Mutations blocking ethylene, jasmonic acid, or ethylene signaling had little effect on metabolite levels. The effects of altering levels of some metabolites were tested by exogenous application during A. brassicicola inoculation. Gamma amino-butyric acid (GABA) or xylitol promoted, while trehalose and ascorbate inhibited, disease severity. GABA promoted, and ascorbate strongly inhibited, fungal growth in culture. Arabidopsis vtc1 and vtc2 mutants, that have low levels of ascorbate, were more susceptible to A. brassicicola. Ascorbate levels declined following A. brassicicola inoculation while levels of dehydroascorbate increased, resulting in a shift of the redox balance between these compounds in the direction of oxidation. These results demonstrate that ascorbate is an important component of resistance to this pathogen.

Arabidopsis PECTIN METHYLESTERASEs Contribute to Immunity against Pseudomonas syringae

“…For A. brassicicola growth assays, at least 15 leaf discs from five to six plants were pooled per biological sample. Disease severity, a proxy of fungal growth, was determined as previously described (Tsuda et al, 2009;Botanga et al, 2012). For PME assays, at least four leaf discs from one plant were combined for each biological sample.…”

Evaluating plant immunity using mass spectrometry-based metabolomics workflows

“…They observed both an increase and decrease in select organic acids and lipids, and an overall increase in potato alkaloids. An Arabidopsis-Alternaria brassicicola interaction study used non-targeted GC-MS and described 128 and 249 molecular features that varied after 9 and 24 h of infection including several sugars, organic acids, and amino acids (Botanga et al, 2012). …”

Response of <i>Arabidopsis</i> Clones to Toxic Compounds Released by Various <i>Rhizoctonia</i> Species

“…Total acorbic acid content in vtc1 clone is about 40% compared to wild type. Earlier work revealed that vtc1 mutant has increased resistance against Pseudomonas syringae or Peronospora parasitica [30] but more sensitive to Alternaria brassicicola [15].…”

“…Regulation of substrate pools such as glutathione or ascorbic acid is the key element of cell protection [11], and the capacity of the biochemical path sustaining the oxido-reductive potential of cells has crucial importance in elimination of harmful free radicals [12] and confers in resistance to pathogens [13,14]. The high level of ascorbic acid reduces the disease severity [15], while the deficiency increases the sensitivity to environmental stress factors [12]. Glutathione S-transferases play an important role in adaptation of various organisms to adverse factors [16][17][18], and in detoxification of electrophilic compounds either exogenic or of natural origin [19,20].…”