A mutation affecting sexual agglutinability in MATα locus of Saccharomyces cerevisiae

Summary A temperature-sensitive non-agglutinative mutant of Saccharomyces cerevisiae was isolated and characterized. The mutation, sag2, affected sexual agglutination, conjugation and production of -mating pheromone at a restrictive temperature, but not the response to -mating pheromone. Genetic analyses showed that the mutation was recessive and in the MAT locus. The sag2 mutation complemented with mat2 but not with mat1 These results suggest that sag2 is in the MAT1 gene and that at a restrictive temperature the mutation, sag2, inactivated the MAT1 product, a positive regulator of -mating functions. The sag2 mutation is like mat1-5 in its retention of response to -mating pheromone. However, at 25 °C, sag2 cells were competent to mate, whereas mat1-5 cells were not. Hence, sag2 is regarded as a new allele in the MAT1 gene, which we designate mat1-11.