Search

Antioxidant molecules play a crucial role in maintaining redox homeostasis, eliminating oxidative damage, and regulating pathogenesis in phytopathogenic fungi. These antioxidants function through a complex regulatory network involving enzymatic scavengers such as the superoxide dismutases (SODs), catalases, thioredoxins, and glutathiones, as well as non-enzymatic molecules. Specifically, the thioredoxin and glutathione systems (AaTrr1, AaTsa1, AaGpx3, and AaGlr1) mediated by NADPH oxidase represent vital thiol antioxidant systems utilized to regulate the detoxification of reactive oxygen species (ROS) in Alternaria alternata. This present study investigated the regulatory roles of AaBemA, a component of the fungal NADPH oxidase (Nox) complex, in the tangerine pathotype of A. alternata. Loss-of-function genetic analysis demonstrated that AaBemA is essential for the accumulation of cellular hydrogen peroxide (H2O2). Mutant strains with defective AaBemA displayed higher sensitivity to H2O2 and the ROS-generating oxidant tert-butyl-hydroperoxide. These phenotypes closely resembled those previously observed in AaNoxB, AaTrr1, AaTsa1, AaGlr1, and AaYap1 mutants, suggesting a potential interconnection among them. Notably, the defective phenotype of ΔAaBemA could be restored through genetic complementation with wildtype AaBemA gene. Subcellular localization of a functional AaBemA fused with green fluorescent protein (GFP) gene under confocal microscope revealed a widespread distribution of green fluorescence in the cytoplasm and cell membrane, indicating high expression of AaBemA during fungal growth in A. alternata. Intriguingly, inactivation of AaBemA did not affect the morphological phenotype and pathogenicity, indicating that the AaBemA is dispensable for the aforementioned phenotypes. To explore the molecular mechanisms underlying the regulation of ROS stress response, we sequenced the whole transcriptomes of A. alternata wildtype and ROS-sensitive mutants (ΔAaBemA, ΔAaNoxB, ΔAaGlr1, ΔAaTrr1, ΔAaTsa1, ΔAaYap1) which displayed considerable sensitivity to oxidants. Comparative transcriptome analysis revealed significant influence on the gene-expression pattern of numerous genes related to glutathione metabolism, cellular oxidant detoxification, cellular response to abiotic stimulus, and cellular response to osmotic stress. The gene-expression data and pathways related to various essential metabolic processes and ROS tolerance enabled us to propose a NADPH oxidase-mediated regulatory network involving NADPH oxidase (AaNoxB, AaBemA), AaYap1, glutaredoxin (AaGPx3, AaGlr1), and thioredoxin systems (AaTrr1, AaTsa1) in responding to ROS stress in A. alternata. [ABSTRACT FROM AUTHOR]

Clarireedia spp. is a destructive phytopathogenic fungus that causes turf dollar spot of bent-grass, leading to widespread lawn death. In this study, we explored the antifungal capability of 6-pentyl-2 H -pyran-2-one (6PP), a natural metabolite volatilized by microorganisms, which plays an important role in the biological control of turfgrass dollar spot. However, the mechanisms by which 6PP inhibits Clarireedia jacksonii remain unknown. In the present study, C. jacksonii mycelial growth was inhibited by the 6PP treatment and the 6PP treatment damaged cell membrane integrity, causing an increase in relative conduc-tivity. Furthermore, physiological and biochemistry assay showed that 6PP treatment can enhance reactive oxygen species (ROS) levels, malondialdehyde (MDA) content obviously increased with 6PP exposure, increased alchohol dehydrogenase (ADH) and depleted acetalde-hyde dehydrogenase (ALDH), and activated the activities of many antioxidant enzymes in C. jacksonii. Gen Ontology and Kyoto Encyclopedia of Genes and Genomes analysis revealed that some genes in C. jacksonii after 6PP treatment related to integrity of the cell wall and membrane, and oxidative stress were significantly downregulated. It is worth mentioning that the fatty acid degradation pathway is significantly upregulated, with an increase in ATP content and ATP synthase activity, which may promote fungal cell apoptosis. Moreover, we found that the expression of ABC transporters, and glutathione metabolism encoding genes were increased to respond to external stimuli. Taken together, these findings revealed the potential antifungal mechanism of 6PP against Clarireedia spp., which also provides a theoretical basis for the commercial utilization of 6PP as a green pesticide in the future. [Display omitted] • 6PP has inhibitory effect on Clarireedia jacksonii. • 6PP causes morphological changes and oxidative damage to C. jacksonii. • 6PP can disturbs energy metabolism and promotes cell apoptosis of C. jacksonii. [ABSTRACT FROM AUTHOR]