title: Absence of repellents in Ustilago maydis induces genes encoding small secreted proteins.
abstract: The rep1 gene of the maize pathogen Ustilago maydis encodes a pre-pro-protein that is processed in the secretory pathway into 11 peptides. These so-called repellents form amphipathic amyloid fibrils at the surface of aerial hyphae. A SG200 strain in which the rep1 gene is inactivated (∆rep1 strain) is affected in aerial hyphae formation. We here assessed changes in global gene expression as a consequence of the inactivation of the rep1 gene. Microarray analysis revealed that only 31 genes in the ∆rep1 SG200 strain had a fold change in expression of ≥2. Twenty-two of these genes were up-regulated and half of them encode small secreted proteins (SSPs) with unknown functions. Seven of the SSP genes and two other genes that are over-expressed in the ∆rep1 SG200 strain encode proteins that can be classified as secreted cysteine-rich proteins (SCRPs). Interestingly, most of the SCRPs are predicted to form amyloids. The SCRP gene um00792 showed the highest up-regulation in the ∆rep1 strain. Using GFP as a reporter, it was shown that this gene is over-expressed in the layer of hyphae at the medium-air interface. Taken together, it is concluded that inactivation of rep1 hardly affects the expression profile of U. maydis, despite the fact that the mutant strain has a strong reduced ability to form aerial hyphae.
authors.affiliation: Department of Microbiology and Kluyver Centre for Genomics of Industrial Fermentations, Faculty of Science, University of Utrecht, The Netherlands. w.r.teertstra@uu.nl
authors.forename: Wieke R
authors.initials: WR
authors.lastname: Teertstra
authors.forename: Pauline
authors.initials: P
authors.lastname: Krijgsheld
authors.forename: Han A B
authors.initials: HA
authors.lastname: Wösten
mesh_terms: D000682:Amyloid / Q000378:metabolism; D015152:Blotting, Northern; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal; D020868:Gene Silencing; D005800:Genes, Fungal; D049452:Green Fluorescent Proteins / Q000378:metabolism; D025301:Hyphae / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D008856:Microscopy, Fluorescence; D020411:Oligonucleotide Array Sequence Analysis; D010455:Peptides / Q000235:genetics / Q000378:metabolism*; D011498:Protein Precursors / Q000235:genetics / Q000378:metabolism*; D020539:Sequence Analysis, Protein; D014170:Transformation, Genetic; D015854:Up-Regulation; D014588:Ustilago / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism
chemical_list: D000682:Amyloid; D005656:Fungal Proteins; D010455:Peptides; D011498:Protein Precursors; C102170:Rep1 protein, Ustilago maydis; D049452:Green Fluorescent Proteins