CALCIUM-ION INFLUX DURING SPORULATION IN THE YEAST SACCHAROMYCES-CEREVISIAE

The changes in intra- and (or) extra-cellular concentrations of Ca2+, Mg2+, K+, and Na+ during sporulation of a MATa/MAT alpha diploid yeast of Saccharomyces cerevisiae were examined in a nutrition-deprived medium with potassium acetate. Among these, Ca2+ in external medium was preferentially incorporated into cells, and sporulation was induced when the magnitude of free Ca2+ gradient between cytosol [Ca2+](i) and external medium [Ca2+](0) reached more than 3 x 10(3) ([Ca2+](i)/[Ca2+](0) = 3.5 x 10(3)). The result indicated that the meiosis and (or) sporulation signal of the yeast S. cerevisiae was generated through elevated Ca2+ influx rather than release from the internal Ca2+ stores.