Abstract
NADPH oxidase is an enzyme that generates reactive oxygen species from oxygen and NADPH and is highly conserved in eukaryotes. In Fusarium graminearum, a series of different Nox enzymes have been identified. NoxA is involved in sexual development and ascospore production and, like NoxB, also contributes to pathogenicity. Both NoxA and NoxB are regulated by the subunit NoxR, whereas NoxC is usually self-regulated by EF-hand motifs found on the enzyme. In this study, we characterized another NADPH oxidase in F. graminearum, FgNoxD. In the FgNoxD deletion mutant, vegetative growth and conidia production were reduced, while sexual development was totally abolished. The FgNoxD deletion mutant also showed reduced resistance to cell wall perturbing agents; cell membrane inhibitors; and osmotic, fungicide, cold, and extracellular oxidative stress, when compared to the wild type. Moreover, in comparison to the wild type, the FgNoxD deletion mutant exhibited reduced virulence against the host plant. The FgNoxD deletion mutant produced less deoxynivalenol than the wild type, and the Tri5 and Tri6 gene expression was also downregulated. In conclusion, our findings show that FgNoxD is involved in the survival against various stresses, conidiation, sexual development, and virulence, highlighting this enzyme as a new target to control the disease caused by F. graminearum.
Highlights
Fusarium graminearum is a homothallic ascomycete fungus that causes Fusarium head blight (FHB) in cereal crops worldwide (Leslie and Summerell, 2006)
To verify whether the observed changes found in the deletion mutant were caused by gene defection, FgNoxD was reintroduced at an alternate site in the deletion mutant (FgNoxD-C; Figure 1B). qRT-PCR showed that the transcripts of FgNoxD were completely abolished in the deletion mutant but was recovered in FgNoxD-C (Figure 1C)
Similar to previous studies on NoxD, our current study showed that FgNoxD in F. graminearum is involved in normal vegetative growth, virulence, asexual development, and resistance to various stressors
Summary
Fusarium graminearum is a homothallic ascomycete fungus that causes Fusarium head blight (FHB) in cereal crops worldwide (Leslie and Summerell, 2006) It produces deoxynivalenol (DON) which inhibits protein synthesis by binding to ribosomes, making it toxic to humans and animals (Desjardins and Proctor, 2007; Pestka, 2010; Chong et al, 2020). Excess ROS, such as superoxide, hydrogen peroxide (H2O2), and hydroxyl radicals, can non- and NADPH Oxidase in Fusarium graminearum rapidly react with other molecules including lipids, proteins, DNA, and carbohydrates (Gutteridge, 1994; Rodriguez and Redman, 2005). These reactions cause DNA mutation, lipid peroxidation, and protein oxidation, resulting in cellular dysfunction and apoptosis (Aguirre et al, 2005; Halliwell and Gutteridge, 2015)
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