Rapid intracellular alkalinization of Saccharomyces cerevisiae MATa cells in response to alpha-factor requires the CDC25 gene product.

The alpha-factor mating pheromone induces a transient intracellular alkalinization of MATa cells within minutes after exposure to the pheromone, and is the earliest biochemical event that can be identified subsequent to the exposure. Dissipation of the pheromone induced pH gradient, using 2,4-dinitrophenol or sodium orthovanadate, does not inhibit the biological response of the yeast to the pheromone such as mating and 'schmoo' formation. These findings suggest that the pheromone mediated pH change per se is not a part of the transmembrane signalling but rather the consequence of a biochemical reaction triggered by the alpha-pheromone interaction with its receptor and may have a permissive effect on the pheromonal response. The cdc25ts mutation causes MATa cells to become nonresponsive to alpha-factor subsequent to a shift to the restrictive temperature, suggesting that the CDC25 gene product participates in the pheromone response pathway.