THE PHEROMONE SIGNAL PATHWAY IN SACCHAROMYCES-CEREVISIAE

Haploid cells of the yeast Saccharomyces cerevisiae normally undergo a budding life cycle, but after binding the appropriate mating pheromone they undergo a different developmental pathway that leads to conjugation. This intercellular communication between the two mating types activates a signal transduction pathway that stimulates the diverse physiological changes required for conjugation, such as induction of cell surface agglutinins, cell division arrest in G1, morphogenesis to form a conjugation tube, and cell fusion. The components of this pathway include a G protein-coupled receptor, several protein kinases, and a pheromone-responsive transcription factor. The molecular mechanisms that transduce the pheromone signal are remarkably similar to the mechanisms of hormone signaling used in multicellular organisms. Thus, the analysis of the pheromone signal pathway in yeast directly contributes to the study of cell growth and development in other eukaryotic organisms.