Switching genes in Schizosaccharomyces pombe.

Area of Science:

• * Molecular biology
• * Genetics
• * Cellular biology

Background:

• * Homothallic (h 90) Schizosaccharomyces pombe strains are used to study mating-type switching.
• * Mutations can reduce the frequency of mating-type switching, leading to observable phenotypes.
• * These mutations can occur in the mating-type locus (mat1) or in unlinked switching (swi) genes.

Purpose of the Study:

• * To characterize newly identified switching (swi) mutants in Schizosaccharomyces pombe.
• * To map the locations of these swi mutations and identify the affected genes.
• * To classify the swi mutants based on their colony phenotypes.

Main Methods:

• * Isolation and characterization of Schizosaccharomyces pombe mutants with reduced mating-type switching frequencies.
• * Analysis of colony morphology and iodine staining reactions to assess switching proficiency.
• * Genetic mapping of mutations to identify linkage groups and specific swi genes.

Main Results:

• * Forty-nine swi mutants were analyzed, mapping to ten distinct swi genes (swi1 to swi10).
• * Seven swi genes were assigned to chromosome I and seven to chromosome II.
• * Two classes of swi mutants were identified: Class I mutants showed only mottled colonies, while Class II mutants displayed both mottled and iodine-negative colonies (predominantly h+).

Conclusions:

• * The study identified and mapped ten essential switching genes (swi1-swi10) involved in mating-type switching in Schizosaccharomyces pombe.
• * Mutations in these swi genes lead to distinct colony phenotypes, allowing for classification into two groups.
• * These findings contribute to understanding the genetic control of mating-type switching in fission yeast.