Colonies of Schizosaccharomyces pombe that contain ascospores (e.g., colonies of homothallic strains) turn black after treatment with iodine vapors. Heterothallic strains of S. pombe normally do not show this reaction. In experiments with the latter strains we found mutants which exhibit a positive iodine reaction though they do not contain ascospores. This phenotype is due to mutations in a ne...

Intratetrad mating, the fusion of gametes formed in a single meiosis, has unusual consequences for genetic diversity, especially in genome regions linked to mating type loci. Here we investigate the fate of modifier alleles that alter the rate of intratetrad mating, under models of heterozygote advantage and of genetic load resulting from recurrent mutation. In both cases, intratetrad mating is...

Studies of heterothallic and homothallic strains of Saccharomyces cerevisiae have led to the suggestion that mating-type information is located at three distinct sites on chromosome 3, although only information at the mating-type (MAT) locus is expressed (Hicks, Strathern and Herskowitz, 1977). We have found that the recessive mutation cmt permits expression of the normally silent copies of mat...

Tha A alpha locus of the basidiomycete fungus, Schizophyllum commune, regulates sexual development via proteins Y and Z. Each A alpha mating type encodes unique Y and Z isoforms. We used two isoforms of Y (Y4 and Y5) and two isoforms of Z (Z4 and Z5) in affinity assays of protein binding. These assays identified two types of protein interactions. Each full-length Y or Z protein binds to itself ...

ANGEHRN and GUTZ (1968) have shown that homozygosity for the matl-M allele in diploid strains of Schizosaccharomyces pombe increases mitotic recombination between his7 and mat2. In this paper, we report that meiotic recombination frequencies can vary from 3.4 to 16.1 percent between his7 and his2 and that this variation is due to the combination of alleles a t the mat i and mat2 loci. HE mating...

Six genic mutations restricting clones to mating type VII (O) were isolated in syngen 4, Paramecium aurelia. The only three extensively tested were neither allelic nor closely linked. A second type of mutation, allelic to one of the O restricted mutants, was also found. Clones homozygous for this mutant gene were selfers, producing both O and E (VIII) mating types, but only when they were proge...

Both A1 and A2 mating types of Phytophthora infestans were detected in El-Behera governorate and the surrounding area where potato and tomato were intensively cultivated during the 2005-2006 growing season. The A2 mating type constituted 14.8% of the total isolates recovered (162) while A1 mating type constituted 83.9%. A 7.4% of the total potato and tomato fields (94) surveyed yielded A2 matin...

Sex chromosomes can display successive steps of recombination suppression known as "evolutionary strata," which are thought to result from the successive linkage of sexually antagonistic genes to sex-determining genes. However, there is little evidence to support this explanation. Here we investigate whether evolutionary strata can evolve without sexual antagonism using fungi that display suppr...

Mating-type genes in fungi encode regulators of mating and sexual development. Heterothallic ascomycete species require different sets of mating-type genes to control nonself-recognition and mating of compatible partners of different mating types. Homothallic (self-fertile) species also carry mating-type genes in their genome that are essential for sexual development. To analyze the molecular b...

Mating-specific adhesion between haploid yeast cells of opposite mating type (a and alpha) was studied by using a quantitative agar plate assay. Washed a and alpha cells that had not previously been exposed to their respective opposite mating type ("naive" cells) adhered relatively weakly. In water, only 5 to 10% of the a cells stuck tightly enough to alpha cells to give rise subsequently to di...