Abstract
The multicomponent NADPH oxidase enzyme complex (Nox) converts molecular oxygen in a stepwise reduction to superoxides leading to the production of H2O2. This study characterized the role of the catalytic subunit (gp91phox) of Nox, NoxA and NoxB in F. graminearum. Targeted deletion of the genes NoxA and NoxB show that they differentially regulate the production of superoxides during mycelial development. The nitro blue tetrazolium staining method revealed that both the single noxA mutant and the double noxA/B mutant strains are restricted in the production of superoxides. This limitation, however, did not affect their ability to synthesize 15-ADON in culture. Deletion analyses also revealed that NoxA, but not NoxB, is involved in perithecia development and ascospore production. An in-vitro based cellophane breach assay indicated that both NoxA and NoxB contribute to virulence. The pathogenicity tests performed on a susceptible variety of wheat, ‘Roblin’, confirmed that these two genes act synergistically to promote virulence. Cumulatively, we provide evidence that the Nox homologues have non-redundant functions in F. graminearum.
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