scholarly journals MAPPING OF THE HOMOTHALLIC GENES, HMα AND HM  a, IN SACCHAROMYCES YEASTS

Genetics ◽  
1976 ◽  
Vol 84 (3) ◽  
pp. 437-451
Author(s):  
Satoshi Harashima ◽  
Yasuji Oshima
Keyword(s):  
Mating Type ◽  
The Other ◽  
Type Locus ◽  
Mating Type Locus ◽  
Direct Linkage ◽  
Expected Values ◽  
Chromosome Iii ◽  
The Right ◽  
Saccharomyces Yeasts ◽  
Three Factor

ABSTRACT Two of the three homothallic genes, HMα and HM  a, showed direct linkage to the mating-type locus at approximately 73 and 98 stranes (57 and 65 centimorgans [cM]), respectively, whereas, the other, HO, showed no linkage to 25 standard markers distributed over 17 chromosomes including the mating-type locus. To determine whether the HMα and HM  a loci located on the left or right side of the mating-type locus, equations for three factor analysis of three linked genes were derived. Tetrad data were collected and were compared with expected values by X2 statistics. Calculations indicated that the HMα gene is probably located on the right arm at 95 stranes (65 cM) from the centromere and the HM  a locus at approximately 90 stranes (64 cM) on the left arm of chromosome III.

A SEARCH FOR COMPLEXITY AT THE MATING-TYPE LOCUS OF NEUROSPORA CRASSA

1973 ◽  
Vol 15 (3) ◽  
pp. 577-585 ◽  
Author(s):  
Dorothy Newmeyer ◽  
H. Branch Howe Jr. ◽  
Donna R. Galeazzi
Keyword(s):  
Neurospora Crassa ◽  
Mating Type ◽  
Adjacent Gene ◽  
Opposite Mating Type ◽  
Type Locus ◽  
Linked Gene ◽  
Heterokaryon Incompatibility ◽  
Mating Type Locus ◽  
Incompatibility Reaction ◽  
The Right

Evidence for complexity at the mating-type locus of Neurospora crassa was sought by selecting recombinants between closely linked markers on either side. All recombinants were tested for crossing ability, to test the hypothesis that the two mating-type alleles are actually closely linked self-sterile mutants; such tests should also detect subunits analogous to the α and β subunits of the A factor of Schizophyllum or Coprinus. No change in crossing ability was found among the 5,019 recombinants tested, representing 235,000 viable ascospores. The results indicate that if subunits exist, they are not more than 0.002 units apart. Twelve hundred and forty of the recombinants were tested in a way that should also have detected subunits analogous to the A and B factors of Schizophyllum and Coprinus, except that A and B would be closely linked. No such subunits were detected.N. crassa strains of opposite mating type are heterokaryon-incompatible during vegetative growth, and observations of various investigators have suggested that the heterokaryon incompatibility might be controlled by a separate closely-linked gene rather than by mating type itself. A sample of the recombinants was therefore tested for separation of the heterokaryon-incompatibility and crossing-compatibility functions. (Heterokaryon-incompatibility was scored by the presence of an incompatibility reaction in duplications heterozygous for mating type; this technique is simple and eliminates complications due to unlinked heterokaryon-incompatibility loci, several of which are known in N. crassa.) No separation was found. The results indicate that if an adjacent gene is responsible for the heterokaryon-incompatibility, it is not more than 0.0078 units from mating type, if on the left, and not more than 0.018 units from mating type, if on the right.

scholarly journals PRECISE MAPPING OF THE HOMOTHALLISM GENES HML AND HMR IN SACCHAROMYCES CEREVISIAE

Genetics ◽  
1980 ◽  
Vol 96 (2) ◽  
pp. 315-320
Author(s):  
Amar J S Klar ◽  
Jean McIndoo ◽  
James B Hicks ◽  
Jeffrey N Strathern
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Mating Type ◽  
Control Mechanism ◽  
Negative Control ◽  
Switching Function ◽  
Novel Approach ◽  
Precise Mapping ◽  
Chromosome Iii ◽  
The Right ◽  
Saccharomyces Yeasts

ABSTRACT The HML and HMR loci carry unexpressed copies of MAT  a and MATα information, and a replica of that information is transposed to MAT during mating-type interchange in Saccharomyces yeasts. A negative control mechanism keeps silent the information located at the HML and HMR loci. We mapped these loci by constructing strains in which these loci are expressed. In these strains, the mating type of the segregants is dependent upon the allele at HML and HMR. This novel approach is independent of their switching function. HML is located on the left arm of chromosome III distal to his4 by about 26.8 centimorgans (cM). HMR maps on the right arm of the same chromosome distal to thr4 by about 39.8 cM and proximal to MAL2 by about 1.0 cM. The results allow the exact placement of these loci and are in accord with the observations made by Harashima and Oshima (1976).

scholarly journals FUNCTIONAL EQUIVALENCE AND CO-DOMINANCE OF HOMOTHALLIC GENES HMα/hmα AND HM  a/hm  a IN SACCHAROMYCES YEASTS

Genetics ◽  
1980 ◽  
Vol 95 (4) ◽  
pp. 819-831
Author(s):  
Satoshi Harashima ◽  
Yasuji Oshima
Keyword(s):  
Mating Type ◽  
The Other ◽  
Functional Equivalence ◽  
Single Pair ◽  
Type Conversion ◽  
Chromosome Iii ◽  
Saccharomyces Yeasts

ABSTRACT The specificity of mating type in Saccharomyces yeasts is controlled by a pair of alleles, a and α, on chromosome III. They are mutually interconverted by the function of three kinds of homothallic genes, each consisting of a single pair of alleles, HO/ho, HMα/hmα and HMa/hma. For the a to α conversion, HO HMα HMa, HO hmα HMa and HO hmα hma genotypes are effective; whereas, the α to a conversion occurs in HO HMα HMa, HO HMα hma and HO hmα hma cells. To explain these observations, Naumov and Tolstorukov (1973) and Harashima, Nogi and Oshima (1974) suggested that hma and HMα are functionally equivalent and effective for the α to a conversion in combination with HO; whereas, hmα and HMa are functionally equivalent and effective for the a to α conversion with the function of HO. To test this idea and to compare it with two other possible mechanisms, some of the tetrad segregants from four kinds of a/a/α/α tetraploids homozygous for the HO allele and for one of the HMα/hmα and HMa/hma loci, while heterozygous for the other one with +/+/-/- configuration, were investigated with respect to their thallism by self-sporulation. Results indicated the functional equivalence of both the HMα and hma alleles and the hmα and HMα alleles in mating-type conversion, and the co-dominance of the alleles of each locus. From these findings and other data, we agree with the revision of the nomenclature of the HMα/hmα and HMa/hma genes to HMRa/HMRα and HMLα/HMLa, respectively.

scholarly journals rme1 Mutation of Saccharomyces cerevisiae: map position and bypass of mating type locus control of sporulation.

1981 ◽  
Vol 1 (10) ◽  
pp. 958-960 ◽  
Author(s):  
J Rine ◽  
G F Sprague ◽  
I Herskowitz
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Mating Type ◽  
Type Locus ◽  
Mating Type Locus ◽  
Type Information

Sporulation in Saccharomyces cerevisiae normally occurs only in MATa/MAT alpha diploids. We show that mutations in RME1 bypassed the requirements for both a and alpha mating type information in sporulation and therefore allowed MATa/MATa and MAT alpha/MAT alpha diploids to sporulate. RME1 was located on chromosome VII, between LEU1 and ADE6.

Transformation of protoplasted yeast cells is directly associated with cell fusion

1984 ◽  
Vol 4 (4) ◽  
pp. 771-778
Author(s):  
S Harashima ◽  
A Takagi ◽  
Y Oshima
Keyword(s):  
Cell Fusion ◽  
Mating Type ◽  
Nuclear Fusion ◽  
Yeast Cells ◽  
Nuclear Markers ◽  
Type Locus ◽  
Mating Type Locus ◽  
Yeast Protoplasts ◽  
Yeast Plasmids ◽  
Binominal Distribution

The frequency of cell fusion during transformation of yeast protoplasts with various yeast plasmids with a chromosome replicon (YRp or YCp) or 2 mu DNA (YEp) was estimated by two methods. In one method, a mixture of protoplasts of two haploid strains with identical mating type and complementary auxotrophic nuclear markers with or without cytoplasmic markers was transformed. When the number of various phenotypic classes of transformants for the nuclear markers was analyzed by equations derived from binominal distribution theory, the frequency of nuclear fusion among the transformants was 42 to 100% in transformations with the YRp or YCp plasmids and 28 to 39% with the YEp plasmids. In another method, a haploid bearing the sir mutation, which allows a diploid (or polyploid) homozygous for the MAT (mating type) locus to sporulate by the expression of the silent mating-type loci HML and HMR, was transformed with the plasmids. Sporulation ability was found in 43 to 95% of the transformants with the YRp or YCp plasmids, and 26 to 31% of the YEp transformants. When cytoplasmic mixing was included with the nuclear fusion, 96 to 100% of the transformants were found to be cell fusants. Based upon these observations, we concluded that transformation of yeast protoplasts is directly associated with cell fusion.

Homothallic mating type switching generates lethal chromosome breaks in rad52 strains of Saccharomyces cerevisiae

1981 ◽  
Vol 1 (6) ◽  
pp. 522-534
Author(s):  
B Weiffenbach ◽  
J E Haber
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Mating Type ◽  
Deoxyribonucleic Acid ◽  
Type Locus ◽  
Mating Type Switching ◽  
Lethal Event ◽  
Bona Fide ◽  
Chromosome Iii ◽  
Mat Locus ◽  
Type Information

In homothallic cells of Saccharomyces cerevisiae, a or alpha mating type information at the mating type locus (MAT) is replaced by the transposition of the opposite mating type allele from HML alpha or HMRa. The rad52-1 mutation, which reduces mitotic and abolishes meiotic recombination, also affects homothallic switching (Malone and Esposito, Proc. Natl. Acad. Sci. U.S.A. 77:503-507, 1980). We have found that both HO rad52 MATa and HO rad52 MAT alpha cells die. This lethality is suppressed by mutations that substantially reduce but do not eliminate homothallic conversions. These mutations map at or near the MAT locus (MAT alpha inc, MATa-inc, MATa stk1) or are unlinked to MAT (HO-1 and swi1). These results suggest that the switching event itself is involved in the lethality. With the exception of swi1, HO rad52 strains carrying one of the above mutations cannot convert mating type at all. MAT alpha rad52 HO swi1 strains apparently can switch MAT alpha to MATa. However, when we analyzed these a maters, we found that few, if any, of them were bona fide MATa cells. These a-like cells were instead either deleted for part of chromosome III distal to and including MAT or had lost the entire third chromosome. Approximately 30% of the time, an a-like cell could be repaired to a normal MATa genotype if the cell was mated to a RAD52 MAT alpha-inc strain. The effects of rad52 were also studied in mata/MAT alpha-inc rad52/rad52 ho/HO diploids. When this diploid attempted to switch mata to MATa, an unstable broken chromosome was generated in nearly every cell. These studies suggest that homothallic switching involves the formation of a double-stranded deoxyribonucleic acid break or a structure which is labile in rad52 cells and results in a broken chromosome. We propose that the production of a double-stranded deoxyribonucleic acid break is the lethal event in rad52 HO cells.

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