title: Biotrophy-specific downregulation of siderophore biosynthesis in Colletotrichum graminicola is required for modulation of immune responses of maize.
abstract: The hemibiotrophic maize pathogen Colletotrichum graminicola synthesizes one intracellular and three secreted siderophores. eGFP fusions with the key siderophore biosynthesis gene, SID1, encoding l-ornithine-N(5) -monooxygenase, suggested that siderophore biosynthesis is rigorously downregulated specifically during biotrophic development. In order to investigate the role of siderophores during vegetative development and pathogenesis, SID1, which is required for synthesis of all siderophores, and the non-ribosomal peptide synthetase gene NPS6, synthesizing secreted siderophores, were deleted. Mutant analyses revealed that siderophores are required for vegetative growth under iron-limiting conditions, conidiation, ROS tolerance, and cell wall integrity. Δsid1 and Δnps6 mutants were hampered in formation of melanized appressoria and impaired in virulence. In agreement with biotrophy-specific downregulation of siderophore biosynthesis, Δsid1 and Δnps6 strains were not affected in biotrophic development, but spread of necrotrophic hyphae was reduced. To address the question why siderophore biosynthesis is specifically downregulated in biotrophic hyphae, maize leaves were infiltrated with siderophores. Siderophore infiltration alone did not induce defence responses, but formation of biotrophic hyphae in siderophore-infiltrated leaves caused dramatically increased ROS formation and transcriptional activation of genes encoding defence-related peroxidases and PR proteins. These data suggest that fungal siderophores modulate the plant immune system.
authors.affiliation: Martin-Luther-Universität Halle-Wittenberg, Interdisziplinäres Zentrum für Nutzpflanzenforschung (IZN), Betty-Heimann-Str. 3, D-06120, Halle (Saale), Germany; Martin-Luther-Universität Halle-Wittenberg, Institut für Agrar- und Ernährungswissenschaften, Phytopathologie und Pflanzenschutz, Betty-Heimann-Str. 3, D-06120, Halle (Saale), Germany.
authors.forename: Emad
authors.initials: E
authors.lastname: Albarouki
authors.forename: Lukas
authors.initials: L
authors.lastname: Schafferer
authors.forename: Fanghua
authors.initials: F
authors.lastname: Ye
authors.forename: Nicolaus
authors.initials: N
authors.lastname: von Wirén
authors.forename: Hubertus
authors.initials: H
authors.lastname: Haas
authors.forename: Holger B
authors.initials: HB
authors.lastname: Deising
mesh_terms: D020231:Colletotrichum / Q000235:genetics* / Q000378:metabolism*; D004271:DNA, Fungal / Q000737:chemistry / Q000235:genetics; D017353:Gene Deletion; D015966:Gene Expression Regulation, Fungal; D006899:Mixed Function Oxygenases / Q000235:genetics; D008969:Molecular Sequence Data; D010453:Peptide Synthases / Q000235:genetics; D017422:Sequence Analysis, DNA; D017262:Siderophores / Q000096:biosynthesis*; D003313:Zea mays / Q000276:immunology* / Q000382:microbiology*
chemical_list: D004271:DNA, Fungal; D017262:Siderophores; D006899:Mixed Function Oxygenases; D010453:Peptide Synthases; C104385:non-ribosomal peptide synthase