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Biotrophy‐specific downregulation of siderophore biosynthesis in C olletotrichum graminicola is required for modulation of immune responses of maize
Author(s) -
Albarouki Emad,
Schafferer Lukas,
Ye Fanghua,
Wirén Nicolaus,
Haas Hubertus,
Deising Holger B.
Publication year - 2014
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/mmi.12561
Subject(s) - siderophore , biology , conidiation , microbiology and biotechnology , hypha , mutant , appressorium , virulence , graminicola , gene , pathogen , biochemistry
Summary The hemibiotrophic maize pathogen C olletotrichum 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. Δ sid1 and Δ nps6 mutants were hampered in formation of melanized appressoria and impaired in virulence. In agreement with biotrophy‐specific downregulation of siderophore biosynthesis, Δ sid1 and Δ nps6 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.