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Maize gene expression during infection with Ustilago maydis strain SG200∆fox1

ABSTRACT: Ustilago maydis is a plant-pathogenic fungus that establishes a biotrophic relationship with its host Zea mays. The biotrophic interaction is initiated upon host penetration, and involves expansion of the host plasma membrane around hyphae, which is thought to facilitate the exchange of nutrients and virulence factors. Transcriptional regulators involved in the establishment of an infectious dikaryon and penetration into the host have been identified, however, regulators involved in the post-penetration stages remained to be elucidated. In the study we report the identification of an Ustilago maydis forkhead transcription factor, Fox1, which is exclusively expressed during biotrophic development. Deletion of fox1 results in reduced virulence and impaired tumour development in planta. Δfox1 hyphae induce plant defences including the overproduction and accumulation of H2O2 in and around infected cells. This oxidative burst acts as an intercellular signal, which elicits a specific host defence response phenotypically represented by the encasement of proliferating hyphae in extensions of the plant cell wall. Maize microarrays experiments were performed to identify genes involved in the observed plant defence responses on leaf tissue infected with U. maydis strain SG200∆fox1 4 dpi.

ORGANISM(S): Zea mays

PROVIDER: GSE19559 | GEO | 2010/12/31

SECONDARY ACCESSION(S): PRJNA122403

REPOSITORIES: GEO

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Project description:The fungus Ustilago maydis is a biotrophic pathogen of corn. In its genome we have identified an ortholog of YAP1 from Saccharomyces cerevisae which regulates the oxidative stress response in this organism. yap1 mutants of U. maydis displayed higher sensitivity to H2O2 than wild type cells and their virulence was significantly reduced. U. maydis yap1 could partially complement the H2O2 sensitivity of a yap1 deletion mutant of S. cerevisiae and a Yap1-GFP fusion protein showed nuclear localization after H2O2 treatment, suggesting that Yap1 in U. maydis functions as a redox sensor. Mutations in two cysteine residues prevented accumulation in the nucleus and the respective mutant strains showed the same virulence phenotype as Dyap1 mutants. DAB staining revealed an accumulation of H2O2 around yap1 mutant hyphae which was absent in wild type. Inhibition of the plant NADPH oxidase prevented this accumulation and restored virulence. During the infection Yap1 showed nuclear localization after penetration up to 2-3 days after infection. Through array analysis a large set of yap1 regulated genes were identified and these included two peroxidase genes. Deletion mutants of these genes were attenuated in virulence. These results suggest that U. maydis is using its yap1 controlled H2O2 detoxification system for coping with early plant defense responses. Keywords: Oxidative stress, yap1 dependent genes, Ustilago maydis Two independent overnight cultures of U. mayidis FB1 and FB1Dyap1 grown in CM-glucose (OD600 0.8) were diluted in 100 ml of the same medium (OD600 0.2) and growth at 28Â° C until an OD600 0.6. The cultures were divided and one half was supplemented with 5mM H2O2. After one hour of exposition to H2O2, cells were harvested by centrifugation and frozen in liquid nitrogen. RNA extraction, purification, cDNA generation, purification and labeling were performed according to standard protocols (Affymetrix). DNA array analysis was performed performed on two biological replicates each, using custom-designed Affymetrix chips (MPIUstilagoA). Data were analysed using a GeneArray Scanner (Agilent/Affymetrix) and the GeneChip Expression Analysis software (GCOS)

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Maize gene expression during infection with Ustilago maydis strain SG200∆fox1

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