Thioredoxinand glutaredoxin systemsrequired for oxidative stress resistance, fungicide sensitivityand virulenceof Alternaria alternata
Hongye Li: Zhejiang University
<div>This study determines the function of thioredoxins and glutaredoxinsin the phytopathogenic fungus <em>Alternaria alternata</em>via analyzing mutants from the targeted deletion of genes encoding thioredoxin peroxidase(<em>Tsa1</em>), thioredoxin reductase (<em>Trr1</em>), glutathione reductase (<em>Glr1</em>) and glutathione synthetases (<em>Gsh1</em> and <em>Gsh2</em>).<em>Trr1</em>,<em> Glr1</em>,<em>Gsh1</em>, <em>Gsh2</em>but not<em> Tsa1 </em>are required for growth and conidiation. Reduced growth and conidiation seen in the <em>Trr1</em> or<em> Glr1 </em>deletion mutant can be restored by glutathione. Deletion mutants showing growth inhibition by oxidantsare defective for H<sub>2</sub>O<sub>2</sub>detoxification and induce smaller lesions on citrus leaves. <em>Trr1</em>, <em>Glr1</em> but not <em>Tsa1 </em>also contribute to NaCl resistance.<em>Glr1</em>is required for sorbitol resistance and responsible for resistance to mancozeb, boscalid but not chlorothalonil fungicides, a novel phenotype that has not been reported in fungi. <em>Trr1 </em>is required for resistance to boscalid and chlorothalonil fungicides while <em>Trr1</em>conferssusceptibility to mancozeb. <em>Tsa1</em> deletion mutant displays wild-type sensitivity to test fungicides. The expression of <em>Tsa1</em> and <em>Trr1</em> is regulated by the oxidative stress responsive regulators Yap1, Hog1 and Skn7. The expression of <em>Tsa1</em> but not <em>Trr1 </em>is also regulated by the NADPH oxidase. The results indicate that the capability to resist oxidative stressis required for virulence of <em>A. alternata</em>.</div>
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