Abstract
SummaryFusarium head blight (FHB) is a disease of the floral tissues of wheat and barley for which highly resistant varieties are not available. Thus, there is a need to identify genes/mechanisms that can be targeted for the control of this devastating disease. Fusarium graminearum is the primary causal agent of FHB in North America. In addition, it also causes Fusarium seedling blight. Fusarium graminearum can also cause disease in the model plant Arabidopsis thaliana. The Arabidopsis–F. graminearum pathosystem has facilitated the identification of targets for the control of disease caused by this fungus. Here, we show that resistance against F. graminearum can be enhanced by flg22, a bacterial microbe‐associated molecular pattern (MAMP). flg22‐induced resistance in Arabidopsis requires its cognate pattern recognition receptor (PRR) FLS2, and is accompanied by the up‐regulation of WRKY29. The expression of WRKY29, which is associated with pattern‐triggered immunity (PTI), is also induced in response to F. graminearum infection. Furthermore, WRKY29 is required for basal resistance as well as flg22‐induced resistance to F. graminearum. Moreover, constitutive expression of WRKY29 in Arabidopsis enhances disease resistance. The PTI pathway is also activated in response to F. graminearum infection of wheat. Furthermore, flg22 application and ectopic expression of WRKY29 enhance FHB resistance in wheat. Thus, we conclude that the PTI pathway provides a target for the control of FHB in wheat. We further show that the ectopic expression of WRKY29 in wheat results in shorter stature and early heading time, traits that are important to wheat breeding.
Highlights
The ascomycetous fungus Fusarium graminearum is an important phytopathogen
We further demonstrate that flg22 application and constitutive expression of Arabidopsis WRKY29 confer enhanced resistance to Fusarium head blight (FHB) in wheat, which is accompanied by stronger expression of pattern-triggered immunity (PTI)-associated genes, supporting our suggestion that the PTI pathway is a target for enhancing resistance to FHB
Fg was infiltrated into Arabidopsis leaves and WRKY29 expression was monitored by real-time reverse transcription-polymerase chain reaction (RT-PCR). flg22 peptide-treated leaves provided the positive control for WRKY29 expression
Summary
The ascomycetous fungus Fusarium graminearum (hereafter referred to as Fg) is an important phytopathogen. In wheat (Triticum aestivum) and barley (Hordeum vulgare), Fg is the primary causal agent of Fusarium head blight (FHB) disease which affects floral tissues (Bai and Shaner, 2004; McMullen et al, 1997a; Xu and Nicholson, 2009). The non-availability of highly resistant wheat and barley cultivars, the practical difficulties with the timing of fungicide application during anthesis and the high humidity conditions when disease threat is the highest further constrain efforts to control FHB (McMullen et al, 1997b; Pirgozliev et al, 2003)
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