Rbf1 induced gene expression in Ustilago maydis

In the phytopathogenic Basidiomcete Ustilago maydis, sexual and pathogenic development are tightly connected and controlled via the b-mating type locus. The b-mating type locus encodes two homeodomain transcription factors, bE and bW, which form an active heterodimeric complex when they are derived from different b-alleles. Rbf1 encodes a zinc-finger transcription factor that is expressed upon formation of an active bE/bW heterodimer. To identify gene regulated by rbf1 independently from b, the b mating type locus was replaced by a copy of rbf1 under control of the arabinose-inducible crg1 promoter (strain CP27). Samples were taken 5h after induction of rbf1 gene expression. Strain JB2, carrying a deletion of the b-locus, was used as control. Strains were grown to an OD600 of 0.4-0.6 at 28°C in liquid array medium: 6.25% (w/v) salt solution, 30 mM L-glutamine, 1% (w/v) glucose, pH 7.0 (filter-sterilized). For induction of the bE and bW genes, cells were inoculated in liquid array medium containing 1% (w/v) arabinose instead of glucose as a carbon source. For induction, cells were washed once with inducing medium. Experiments were performed in two biological replicates for each time point.