SITE OF PHEROMONE ACTION AND SECRETION PATHWAY OF A SEXUAL AGGLUTINATION SUBSTANCE DURING ITS INDUCTION BY PHEROMONE-A IN ALPHA-CELLS OF SACCHAROMYCES-CEREVISIAE

In Saccharomyces cerevisiae a mating-type strains carrying the sec1, sec7 and sec18 genes, pheromone a induces .alpha. agglutination ability at 24.degree. C, but not at 36.degree. C. Even when cells were treated at 36.degree. C, a biologically active .alpha. agglutination substance was found in cytoplasm although this activity was not detected in the cell surface fraction. These 36.degree. C-treated cells became agglutinable with a concomitant appearance of .alpha. agglutination substance activity in the cell surface fraction. The cells remained agglutinable even when the treatment temperature was dropped to 24.degree. C under conditions where no de novo synthesis of the agglutination substance occurred. These results indicate that the .alpha. agglutination substance is transported through the yeast secretory pathway and that pheromone a acts at the step of synthesis of the precursor molecule of the .alpha. agglutination substance, similar to the case of the .alpha.-pheromone-induction of the a agglutination substance. Differences in the action of the sex pheromones between agglutination ability induction and induction of G1 arrest of shmooing is discussed.