Pseudohyphal and invasive growth in Saccharomyces cerevisiae

Cells of the yeast Saccharomyces cerevisiae can undergo profound molecular, physiological and morphological modifications in response to a limited supply of essential nutrients, in particular carbon or nitrogen sources. These include a shift in transcription patterns, the modification of the cell cycle, a change in budding pattern and strongly polarised growth. Cells having undergone these modifications do not separate after cell division is completed and form chains of elongated cells called pseudohyphae or filaments. Cells growing as filaments are able to invade agar plates and other substrates, a phenomenon referred to as invasive growth. A network of signal transduction pathways governs this switch from yeast-like growth to pseudohyphal and invasive growth. Important elements of this network have been identified, including nutrient signal-receptors, GTP-binding proteins, components of the pheromone-dependent MAP kinase cascade, cAMP, and several transcription factors. In this review, we summarise our current knowledge in this rapidly progressing field. We focus particularly on the interactions between several signal transduction modules and on the different transcription factors, which are regulated by these signalling modules.