Resumen en inglés

Phosphate regulation in fungi is controlled by the PHO signaling pathway, in which the transcription factor Pho4 and associated regulators govern phosphate uptake, storage, and stress adaptation. While this pathway is established as a determinant of virulence in Candida albicans and Cryptococcus neoformans, its role in Malassezia spp., remains unexplored. Malassezia pachydermatis, a lipid-dependent basidiomycetous yeast of veterinary and human medical relevance, is frequently implicated in canine dermatitis and otitis as well as opportunistic bloodstream infections in humans. In this study, we employed an integrative approach to elucidate the phosphate regulatory framework of M. pachydermatis. Using Hidden Markov Models built from curated PHO protein families, we identified candidate orthologs sharing conserved domains, regulatory motifs, and phylogenetic clustering with PHO-like regulators. STRING-based interaction analyses further supported the functional connectivity of these candidates within a phosphate-responsive network. Experimentally, we evaluated acid phosphatase secretion under phosphate deprivation and growth dynamics under phosphate-limiting conditions, establishing phenotypic correlates of phosphate regulation. Collectively, our results suggest for the first time a set of putative PHO components in M. pachydermatis, highlighting shared structural and functional features with canonical PHO regulators, and providing a framework for future genetic interrogation of phosphate homeostasis and its contribution to pathogenicity.