A MAP kinase cascade composed of cell type specific and non-specific elements controls mating and differentiation of the fungal pathogen Cryptococcus neoformans.

Cryptococcus neoformans is an opportunistic fungal pathogen with a defined sexual cycle in which the alpha allele of the mating type locus is linked to virulence and haploid differentiation. Here we analysed a conserved MAP kinase cascade composed of mating-type specific (Ste11alpha, Ste12alpha) and non-specific (Ste7, Cpk1) elements. Gene disruption experiments demonstrate that this specialized MAP kinase pathway is required for both mating and cell type-specific differentiation but not for virulence. The Ste11alpha, Ste7 and Cpk1 kinases were found to act as a co-ordinate signalling module, whereas the Ste12alpha transcription factor functions with a redundant partner or in a branched or parallel signalling pathway. Our studies illustrate how MAP kinase cascades can be constructed from cell type-specific and non-specific components, yielding pathways that contribute to cell type-specific patterns of signalling and differentiation.