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A nonribosomal peptide synthetase mediates siderophore production and virulence in the citrus fungal pathogen Alternaria alternata.


ABSTRACT: Alternaria species produce and excrete dimethyl coprogen siderophores to acquire iron. The Alternaria alternata gene AaNPS6, encoding a polypeptide analogous to fungal nonribosomal peptide synthetases, was found to be required for the production of siderophores and virulence on citrus. Siderophores purified from culture filtrates of the wild-type strain did not induce any phytotoxicity on the leaves of citrus. Fungal strains lacking AaNPS6 produced little or no detectable extracellular siderophores and displayed an increased sensitivity to H?O?, superoxide-generating compounds (KO? and menadione) and iron depletion. ?nps6 mutants were also defective for the production of melanin and conidia. The introduction of a wild-type AaNPS6 under the control of its endogenous promoter to a ?nps6 null mutant at least partially restored siderophore production and virulence to citrus, demonstrating a functional link between iron uptake and fungal pathogenesis. Elevated sensitivity to H?O?, seen for the ?nps6 null strain could be relieved by exogenous application of ferric iron. The expression of the AaNPS6 gene was highly up-regulated under low-iron conditions and apparently controlled by the redox-responsive yeast transcriptional regulator YAP1. Hence, the maintenance of iron homeostasis via siderophore-mediated iron uptake also plays an important role in resistance to toxic reactive oxygen species (ROS). Our results demonstrate further the critical role of ROS detoxification for the pathogenicity of A.?alternata in citrus.

SUBMITTER: Chen LH 

PROVIDER: S-EPMC6638914 | biostudies-literature | 2013 Jun

REPOSITORIES: biostudies-literature

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A nonribosomal peptide synthetase mediates siderophore production and virulence in the citrus fungal pathogen Alternaria alternata.

Chen Li-Hung LH   Lin Ching-Hsuan CH   Chung Kuang-Ren KR  

Molecular plant pathology 20130226 5


Alternaria species produce and excrete dimethyl coprogen siderophores to acquire iron. The Alternaria alternata gene AaNPS6, encoding a polypeptide analogous to fungal nonribosomal peptide synthetases, was found to be required for the production of siderophores and virulence on citrus. Siderophores purified from culture filtrates of the wild-type strain did not induce any phytotoxicity on the leaves of citrus. Fungal strains lacking AaNPS6 produced little or no detectable extracellular sideropho  ...[more]

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