Tec1, a member of the TEA transcription factors family, is involved in virulence and basidiocarp development in Ustilago maydis

The life cycle of Ustilago maydis involves alternation of a haploid saprophytic yeast-like stage and a dikaryotic hyphal virulent form. Under in vitro conditions, basidiocarps are formed. Analysis of the transcriptional network of basidiocarp formation revealed the possible involvement of a Tec transcription factor (Tec1, UMAG_02835) in the process. In some Ascomycota, Tec factors are involved in mycelial formation, pathogenesis, and interaction with other regulatory elements, but their role in Basidiomycota species is almost unknown. Accordingly, we proceeded to determine the role of this gene in U. maydis by its mutation. Tec1 was found to be a crucial factor for normal mating, basidiocarp development, and virulence, all of the functions related to the dikaryotic stage dependent of the b genes, whereas dimorphism and resistance to different stress conditions occurring in the haploid stage were not affected in tec1 mutants. The observation that mutants showed a low residual wild-type phenotype suggests the presence of a secondary mechanism that partially compensates the loss of Tec1.