Temperature-mediated inactivation of the b heterodimer during biotrophic development of U. maydis

ABSTRACT: In fungi, sexual compatibility is controlled by mating type loci that prevent self-fertilization. In the plant pathogenic fungus Ustilago maydis, the b mating type locus encodes a pair of unrelated homeodomain proteins, termed bE and bW. After fusion of two compatible, haploid cells, the bE and bW proteins form a heterodimeric complex, but only if they are derived from different, compatible alleles. The active bE/bW complex is required and sufficient to initiate pathogenic development of U. maydis, which is prerequisite for sexual reproduction of the fungus. However, the role of the b heterodimer during later stages of pathogenic development was unclear. To analyze b function during in planta development, we generated a temperature-sensitive bE allele (bEts) encoding a protein with a single amino acid alteration at the border of the homeodomain. This mutation leads to a stop in pathogenic development at the restrictive temperature in planta, while bEts strains show normal development at permissive temperature. At restrictive temperature, hyphae develop enlarged, bulbous cells at their tips that contain multiple nuclei, indicating a severe defect in cell division. DNA array analysis of bEts mutant strains in planta revealed a b-dependent regulation of genes coding for secreted proteins that were shown to influence fungal virulence. Our data demonstrate that in U. maydis the b heterodimer is not only essential to establish the heterodikaryon after mating of two compatible sporidia and to initiate fungal pathogenicity, but also to sustain in planta proliferation and ensure sexual reproduction.

ORGANISM(S): Ustilago maydis

PROVIDER: GSE16501 | GEO | 2009/06/11

SECONDARY ACCESSION(S): PRJNA116123

REPOSITORIES: GEO