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Functional Analysis of FgNahG Clarifies the Contribution of Salicylic Acid to Wheat (Triticum aestivum) Resistance against Fusarium Head Blight

点击数:发布时间:2019-02-01 09:14:49 来源:

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1
State Key Laboratory of Crop Genetics of Disease Resistance and Disease Control, Chengdu 611130, China
2
Triticeae Research Institute, Sichuan Agricultural University, Chengdu 611130, China
Theses authors contributed equally to this work.

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.

Keywords:
salicylic acid; hydroxylase; catechol; mycotoxin; defense