title: Resistance to oxidative stress via regulating siderophore-mediated iron acquisition by the citrus fungal pathogen Alternaria alternata.
abstract: The ability of the necrotrophic fungus Alternaria alternata to detoxify reactive oxygen species (ROS) is crucial for pathogenesis to citrus. We report regulation of siderophore-mediated iron acquisition and ROS resistance by the NADPH oxidase (NOX), the redox activating yes-associated protein 1 (YAP1) regulator, and the high-osmolarity glycerol 1 (HOG1) mitogen-activated protein kinase (MAPK). The A. alternata nonribosomal peptide synthetase (NPS6) is essential for the biosynthesis of siderophores, contributing to iron uptake under low-iron conditions. Fungal strains impaired for NOX, YAP1, HOG1 or NPS6 all display increased sensitivity to ROS. Exogenous addition of iron at least partially rescues ROS sensitivity seen for NPS6, YAP1, HOG1, and NOX mutants. Importantly, expression of the NPS6 gene and biosynthesis of siderophores are regulated by NOX, YAP1 and HOG1, supporting a functional link among these regulatory pathways. Although iron fully rescues H2O2 sensitivity seen in mutants impaired for the response regulator SKN7, neither expression of NPS6 nor biosynthesis of siderophores is controlled by SKN7. Our results indicate that the acquisition of environmental iron has profound effects on ROS detoxification.
authors.affiliation: Citrus Research and Education Center, Institute of Food and Agricultural Sciences (IFAS), University of Florida, 700 Experiment Station Road, Lake Alfred, FL 33850, USA.
authors.forename: Li-Hung
authors.initials: LH
authors.lastname: Chen
authors.affiliation: Department of Plant Pathology, IFAS, University of Florida, Gainesville, FL 32611, USA.|Citrus Research and Education Center, Institute of Food and Agricultural Sciences (IFAS), University of Florida, 700 Experiment Station Road, Lake Alfred, FL 33850, USA.
authors.forename: Siwy Ling
authors.initials: SL
authors.lastname: Yang
authors.affiliation: Department of Plant Pathology, IFAS, University of Florida, Gainesville, FL 32611, USA.|Citrus Research and Education Center, Institute of Food and Agricultural Sciences (IFAS), University of Florida, 700 Experiment Station Road, Lake Alfred, FL 33850, USA.
authors.forename: Kuang-Ren
authors.initials: KR
authors.lastname: Chung
mesh_terms: D000528:Alternaria / Q000235:genetics / Q000502:physiology*; D002957:Citrus / Q000382:microbiology; D005656:Fungal Proteins / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal; D055786:Gene Knockout Techniques; D007501:Iron / Q000378:metabolism*; D050296:Microbial Viability / Q000187:drug effects; D018384:Oxidative Stress; D017262:Siderophores / Q000378:metabolism*; D013312:Stress, Physiological
chemical_list: D005656:Fungal Proteins; D017262:Siderophores; D007501:Iron