Abstract
Salicylic acid (SA) is a key defense hormone associated with wheat resistance against Fusarium head blight, which is a severe disease mainly caused by Fusarium graminearum. Although F. graminearum can metabolize SA, it remains unclear how this metabolic activity affects the wheat–F. graminearum interaction. In this study, we identified a salicylate hydroxylase gene (FG05_08116; FgNahG) in F. graminearum. This gene encodes a protein that catalyzes the conversion of SA to catechol. Additionally, FgNahG was widely distributed within hyphae. Disrupting the FgNahG gene (ΔFgNahG) led to enhanced sensitivity to SA, increased accumulation of SA in wheat spikes during the early infection stage and inhibited development of head blight symptoms. However, FgNahG did not affect mycotoxin production. Re-introducing a functional FgNahG gene into the ΔFgNahG mutant recovered the wild-type phenotype. Moreover, the expression of FgNahG in transgenic Arabidopsis thaliana decreased the SA concentration and the resistance of leaves to F. graminearum. These results indicate that the endogenous SA in wheat influences the resistance against F. graminearum. Furthermore, the capacity to metabolize SA is an important factor affecting the ability of F. graminearum to infect wheat plants.
Highlights
Toxins 2019, 11, x FOR PEER REVIEWSalicylic acid (SA) is a key signaling molecule for regulating plant resistance to diverse pathogens.It triggers acquired resistance (SAR) and expression of a setofofH genes encoding encoding systemic pathogenesis-related (PR) proteins as induces well asthe the accumulation 2O2 [1,2].The pathogenesis-related proteins well as the H2 O2 [1,2]
The extracts from the control E. coli strain did not induce any significant purified and renatured extracts from the control E. coli strain did not changes in the SA content between 0 and 1.5 h. These results indicated that FgNahG encodes a induce any significant changes in the SA content between 0 and 1.5 h. These results indicated that salicylate hydroxylase that catalyzes the conversion of SA to catechol (Figure 1)
Of 18 significant differences in the SA levels in spikes inoculated with the ∆FgNahG or WT strains 8(Figure. These results indicated that SA is more important for wheat resistance against F. graminearum during strains (Figure 7f)
Summary
Toxins 2019, 11, x FOR PEER REVIEWSalicylic acid (SA) is a key signaling molecule for regulating plant resistance to diverse pathogens.It triggers acquired resistance (SAR) and expression of a setofofH genes encoding encoding systemic pathogenesis-related (PR) proteins as induces well asthe the accumulation 2O2 [1,2].The pathogenesis-related proteins well as the H2 O2 [1,2]. Salicylic acid (SA) is a key signaling molecule for regulating plant resistance to diverse pathogens. It triggers acquired resistance (SAR) and expression of a setofofH genes encoding encoding systemic pathogenesis-related (PR) proteins as induces well asthe the accumulation 2O2 [1,2]. Plants mainlyasinvolves theaccumulation phenylalanineofammonia lyase pathwayofand in plants mainly involves the phenylalanine ammonia lyase (PAL). Pathway and the isochorismate the isochorismate synthase (ICS) pathway [3,4]. Both pathways use the same primary metabolite, synthase (ICS)
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