title: A maize-specifically expressed gene cluster in Ustilago maydis.
abstract: The corn pathogen Ustilago maydis requires its host plant maize for development and completion of its sexual cycle. We have identified the fungal mig2-1 gene as being specifically expressed during this biotrophic stage. Intriguingly, mig2-1 is part of a gene cluster comprising five highly homologous and similarly regulated genes designated mig2-1 to mig2-5. Deletion analysis of the mig2-1 promoter provides evidence for negative and positive regulation. The predicted polypeptides of all five genes lack significant homologies to known genes but have characteristic N-terminal secretion sequences. The secretion signals of mig2-1 and mig2-5 were shown to be functional, and secretion of a full length Mig2-1-eGFP fusion protein to the extracellular space was demonstrated. The central domains of the Mig2 proteins are highly variable whereas the C-termini are strongly conserved and share a characteristic pattern of eight cysteine residues. The mig2 gene cluster was conserved in a wide collection of U. maydis strains. Interestingly, some U. maydis isolates from South America had lost the mig2-4 gene as a result of a homologous recombination event. Furthermore, the related Ustilago scitaminea strain, which is pathogenic on sugar cane, appears to lack the mig2 cluster. We describe a model of how the mig2 cluster might have evolved and discuss its possible role in governing host interaction.
authors.affiliation: Institut für Genetik und Mikrobiologie der Universität München, D-80638 München, Germany. basse@mailer.uni-marburg.de
authors.forename: Christoph W
authors.initials: CW
authors.lastname: Basse
authors.forename: Sebastian
authors.initials: S
authors.lastname: Kolb
authors.forename: Regine
authors.initials: R
authors.lastname: Kahmann
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D002874:Chromosome Mapping; D004271:DNA, Fungal; D005656:Fungal Proteins / Q000235:genetics*; D015870:Gene Expression; D005800:Genes, Fungal; D008969:Molecular Sequence Data; D005810:Multigene Family; D016296:Mutagenesis; D011401:Promoter Regions, Genetic; D017386:Sequence Homology, Amino Acid; D013020:South America; D014588:Ustilago / Q000235:genetics*; D003313:Zea mays
chemical_list: D004271:DNA, Fungal; D005656:Fungal Proteins