A Ferroxidation/Permeation Iron Uptake System Is Required for Virulence inUstilago maydis

Abstract

In the smut fungus Ustilago maydis, a tightly regulated cAMP signaling cascade is necessary for pathogenic development. Transcriptome analysis using whole genome microarrays set up to identify putative target genes of the protein kinase A catalytic subunit Adr1 revealed nine genes with putative functions in two high-affinity iron uptake systems. These genes locate to three gene clusters on different chromosomes and include the previously identified complementing siderophore auxotroph genes sid1 and sid2 involved in siderophore biosynthesis. Transcription of all nine genes plus three additional genes associated with the gene clusters was also coregulated by iron through the Urbs1 transcription factor. Two components of a high-affinity iron uptake system were characterized in more detail: fer2, encoding a high-affinity iron permease; and fer1, encoding an iron multicopper oxidase. Fer2 localized to the plasma membrane and complemented an ftr1 mutant of Saccharomyces cerevisiae lacking a high-affinity iron permease. During pathogenic development, fer2 expression was confined to the phase of hyphal proliferation inside the plant. fer2 as well as fer1 deletion mutants were strongly affected in virulence. These data highlight the importance of the high-affinity iron uptake system via an iron permease and a multicopper oxidase for biotrophic development in the U. maydis/maize (Zea mays) pathosystem.

AnUstilago maydisGene Involved in H2O2 Detoxification Is Required for Virulence

“…DNA array analysis was performed on two biological replicates each, using custom-designed Affymetrix chips (MPIUstilagoA). Data were analyzed using a GeneArray Scanner (Agilent/Affymetrix) and GeneChip Expression Analysis software (GCOS) Microarray Suite 5.0 (Affymetrix) as described (Eichhorn et al, 2006). Data analysis was performed using the Biconductor R package (http://www.bioconductor.…”

“…Data analysis was performed using the Biconductor R package (http://www.bioconductor. org/) as described (Eichhorn et al, 2006). The P values for the coefficients/contrasts of interest were adjusted for multiple testing by the false discovery rate method (Benjamini and Hochberg, 1995).…”

TheUstilago maydisClp1 Protein Orchestrates Pheromone andb-Dependent Signaling Pathways to Coordinate the Cell Cycle and Pathogenic Development

“…gsf.de/genre/proj/ustilago/. Target preparation, hybridization, and data acquisition were performed essentially as described before (Eichhorn et al, 2006), with the following alterations: 5 mg RNA were used for firststrand cDNA synthesis at 508C with Superscript II (Invitrogen). Software dChip1.3 (Li and Wong, 2003) was used to calculate mean expression values and fold changes based on a 90% confidence interval (lower bound of fold change), allowing a conservative evaluation of fold change (Li and Wong, 2001).…”

Roles of Iron in Plant Defence and Fungal Virulence

“…hordei conidia express the multicopper oxidase gene FET3, 19 which is required for full virulence in U. maydis. 17 In light of our data showing the induction of wheat PR genes following DFO treatment, it is tempting to consider that pathogen produced siderophores may in fact work as pathogen-associated molecular patterns (PAMPS) in triggering host defences. All known plant pathogenic fungi that require siderophore production for virulence are necrotrophs, 14 which are not as sensitive to recognition by the host as biotrophs.…”

“…Interestingly, siderophore production is not required for virulence in the basidiomycetes Ustilago maydis 15 and Microbotryum violaceum, 16 but loss of the ferroxidase/permease system of reductive iron uptake leads to a reduction in U. maydis virulence. 17 On the surface, it seems convenient to attribute these different modes of infection-related iron uptake to the taxonomic distance between ascomycetes and basidiomycetes. However, neither Saccharomyces cerevisiae nor Candida albicans can produce or secrete siderophores 13 and B. graminis f. sp.…”