Thioredoxin and glutaredoxin systems required for oxidative stress resistance, fungicide sensitivity and virulence of Alternaria alternata.

This study determines the function of thioredoxin and glutaredoxin systems in the phytopathogenic fungus Alternaria alternata via analyzing mutants from the targeted deletion of genes encoding thioredoxin peroxidase (Tsa1), thioredoxin reductase (Trr1) and glutathione reductase (Glr1). Trr1, Glr1 but not Tsa1 are required for growth and conidiation. Reduced growth and conidiation seen in the Trr1 or Glr1 deletion mutant can be restored by glutathione. Deletion mutants showing growth inhibition by oxidants are defective for H2O2 detoxification and induce smaller lesions on citrus leaves. Trr1, Glr1 but not Tsa1 also contribute to NaCl resistance. Glr1 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. Trr1 is required for resistance to boscalid and chlorothalonil fungicides but confers susceptibility to mancozeb. Tsa1 deletion mutant displays wild-type sensitivity to tested fungicides. The expression of Tsa1 and Trr1 is regulated by the oxidative stress responsive regulators Yap1, Hog1 and Skn7. The expression of Tsa1 but not Trr1 is also regulated indirectly by the NADPH oxidase. The results indicate that the capability to resist oxidative stress is required for virulence of A. alternataIMPORTANCE Thioredoxin and glutaredoxin systems are important thiol antioxidant systems in cells and knowledge of these two systems in plant pathogenic fungus A. alte...

Source: Applied and Environmental Microbiology - May 11, 2018 Category: Microbiology Authors: Ma H, Wang M, Gai Y, Fu H, Zhang B, Ruan R, Chung KR, Li H Tags: Appl Environ Microbiol Source Type: research