validamycins and Disease-Resistance

Validamycin, known to interfere with fungal energy metabolism by inhibiting trehalase, has been extensively used to control plant diseases caused by Rhizoctonia spp. However, the effect of validamycin on controlling Fusarium graminearum has not been previously reported. In this study, when applied to F. graminearum in vitro, validamycin inhibited the synthesis of deoxynivalenol (DON), which is a mycotoxin and virulence factor, by decreasing trehalase activity and the production of glucose and pyruvate, which are precursors of DON biosynthesis. Because FgNTH encodes the main trehalase in F. graminearum, these effects were nullified in the FgNTH deletion mutant ΔFgNTH but restored in the complemented strain ΔFgNTHC. In addition, validamycin also increased the expression of pathogenesis-related genes (PRs) PR1, PR2, and PR5 in wheat, inducing resistance responses of wheat against F. graminearum. Therefore, validamycin exhibits dual efficacies on controlling Fusarium head blight (FHB) caused by F. graminearum: inhibition of DON biosynthesis and induction of host resistance. In addition, field trials further confirmed that validamycin increased FHB control and reduced DON contamination in grain. Control of FHB and DON contamination by validamycin increased when the antibiotic was applied with the triazole fungicide metconazole. Overall, this study is a successful case from foundational research to applied research, providing useful information for wheat protection programs against toxigenic fungi responsible for FHB and the consequent mycotoxin accumulation in grains.

Topics: Disease Resistance; Fungal Proteins; Fungicides, Industrial; Fusarium; Genes, Plant; Host-Pathogen Interactions; Inositol; Plant Diseases; Trichothecenes; Triticum; Virulence

In Arabidopsis thaliana the induction of plant trehalase during clubroot disease was proposed to act as a defense mechanism in the susceptible accession Col-0, which could thereby cope with the accumulation of pathogen-synthesized trehalose. In the present study, we assessed trehalose activity and tolerance to trehalose in the clubroot partially resistant accession Bur-0. We compared both accessions for several trehalose-related physiological traits during clubroot infection. A quantitative trait loci (QTLs) analysis of tolerance to exogenous trehalose was also conducted on a Bur-0xCol-0 RIL progeny. Trehalase activity was not induced by clubroot in Bur-0 and the inhibition of trehalase by validamycin treatments resulted in the enhancement of clubroot symptoms only in Col-0. In pathogen-free cultures, Bur-0 showed less trehalose-induced toxicity symptoms than Col-0. A QTL analysis identified one locus involved in tolerance to trehalose overlapping the confidence interval of a QTL for resistance to Plasmodiophora brassicae. This colocalization was confirmed using heterogeneous inbred family (HIF) lines. Although not based on trehalose catabolism capacity, partial resistance to clubroot is to some extent related to the tolerance to trehalose accumulation in Bur-0. These findings support an original model where contrasting primary metabolism-related regulations could contribute to the partial resistance to a plant pathogen.

Topics: Arabidopsis; Carbohydrate Metabolism; Disease Resistance; Inositol; Plant Diseases; Plant Roots; Plasmodiophorida; Polymerase Chain Reaction; Quantitative Trait Loci; Trehalase; Trehalose