Mutants of Saccharomyces cerevisiae that block intervacuole vesicular traffic and vacuole division and segregation.

Intervacuole vesicular exchange and the segregation of parental vacuole material into the bud are strikingly impaired in a temperature-sensitive yeast mutant, vac1-1. At the nonpermissive temperature, haploid vac1-1 cells show a pronounced delay in separation of mature buds from the mother cell and accumulate cells with multiple buds. At both the permissive and restrictive temperatures, daughter cells are produced that lack a detectable vacuole or contain a very small vacuole. In zygotes, vacuoles from a vac1-1 strain are defective as donors, or recipients, of the vesicles of intervacuole vesicular traffic. These defects are specific for the vacuole in that the segregation of nuclear DNA and of mitochondria into the bud appears normal. The isolation of the vac1-1 mutation is a first step in the genetic characterization of vacuole division and segregation.