scholarly journals MUTATIONS AFFECTING SEXUAL CONJUGATION AND RELATED PROCESSES IN SACCHAROMYCES CEREVISIAE. II. GENETIC ANALYSIS OF NONMATING MUTANTS

Genetics ◽  
1974 ◽  
Vol 76 (2) ◽  
pp. 273-288
Author(s):  
Vivian Mackay ◽  
Thomas R Manney
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Genetic Analysis ◽  
Mating Type ◽  
Tetrad Analysis ◽  
Genetic Loci ◽  
Type Locus ◽  
Mating Type Locus

ABSTRACT Rare diploids formed by sterile mutants have been studied by tetrad analysis. Sixteen classes of mutants representing at least five distinct genetic loci have been defined. One group of mutations, isolated only in α, maps at the mating-type locus, while none of the others shows any linkage to mating type. Some of the mutations are nonspecific for mating type, while others act only on a or α. In addition, mutations were found that prevent sporulation when heterozygous in diploids. These appear to be mutations of the mating-type alleles.

scholarly journals GENE CONVERSION OF THE MATING-TYPE LOCUS IN SACCHAROMYCES CEREVISIAE

Genetics ◽  
1979 ◽  
Vol 92 (3) ◽  
pp. 777-782
Author(s):  
Amar J S Klar ◽  
Seymour Fogel ◽  
Karin Lusnak
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Gene Conversion ◽  
Mating Type ◽  
Tetrad Analysis ◽  
Type Locus ◽  
Mating Type Locus ◽  
Gene Conversions

ABSTRACT Tetrad analysis of MAT  a/MATα diploids of Saccharomyces cerevisiae generally yields 2 MATa:2MATα meiotic products. About 1 to 1.8% of the tetrads yield aberrant segregations for this marker. Described here are experiments that determine whether the aberrant meiotic segregations at the mating-type locus are ascribable to gene conversions or to MAT switches, that is, to mating-type interconversions. Diploid strains incapable of switching MAT  a to MATα, or the converse, nevertheless display changes of MAT  a to MATα, or the reverse. These events must be attributed to gene conversion. Further, we suggest that MAT  a and MATα alleles may represent nonhomologous sequences of DNA since they fail to display postmeiotic segregations.

scholarly journals SWITCHING OF A MATING-TYPE a MUTANT ALLELE IN BUDDING YEAST SACCHAROMYCES CEREVISIAE

Genetics ◽  
1979 ◽  
Vol 92 (3) ◽  
pp. 759-776
Author(s):  
Amar J S Klar ◽  
Seymour Fogel ◽  
David N Radin
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Mating Type ◽  
Mutant Allele ◽  
Budding Yeast ◽  
High Capacity ◽  
Tetrad Analysis ◽  
Yeast Saccharomyces Cerevisiae ◽  
Type Locus ◽  
Mating Type Locus ◽  
Parental Allele

ABSTRACT Aimed at investigating the recovery of a specific mutant allele of the mating type locus (MAT) by switching a defective MAT allele, these experiments provide information bearing on several models proposed for MAT interconversion in bakers yeast, Saccharomyces cerevisiae. Hybrids between heterothallic (ho) cells carrying a mutant MAT  a allele, designated mata-2, and MATα ho strains show a high capacity for mating with MAT  a strains. The MATα/mata-2 diploids do not sporulate. However, zygotic clones obtained by mating MATa homothallic (HO) cells with mata-2 ho cells are unable to mate and can sporulate. Tetrad analysis of such clones revealed two diploid (MATa/MATa) :two haploid segregants. Therefore, MAT switches occw in MATα/mata-2 HO/ho cells to produce MATα/MAT a cells capable of sporulation. In heterothallic strains, the mata-2 allele can be switched to a functional MATα and subsequently to a functional MATa. Among 32 MATα to MATa switches tested, where the MATα was previously derived from the mata-2 mutant, only one mata-2 like isolate was observed. However, the recovered allele, unlike the parental allele, conplements the matα stel-5 mutant, suggesting that these alleles are not identical and that the recovered allele presumably arose as a mutation of the MATα locus. No mata-2 was recovered by HO-mediated switching of MATα (previously obtained from mata-2 by HO) in 217 switches analyzed. We conclude that in homothallic and heterothallic strains, the mata-2 allele can be readily switched to a functional MATα and subsequently to a functional MATa locus. Overall, the results are in accord with the cassette model (HICKS, STRATKERN and HERSKO-WITZ 1977b) proposed to explain MAT interconversions.

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.

INTERCONVERSION OF YEAST MATING TYPES II. RESTORATION OF MATING ABILITY TO STERILE MUTANTS IN HOMOTHALLIC AND HETEROTHALLIC STRAINS

Genetics ◽  
1977 ◽  
Vol 85 (3) ◽  
pp. 373A-393
Author(s):  
James B Hicks ◽  
Ira Herskowitz
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Mating Type ◽  
Yeast Cells ◽  
Mating Types ◽  
Yeast Saccharomyces Cerevisiae ◽  
Type Locus ◽  
Mating Ability ◽  
Mating Type Locus ◽  
Regulatory Information ◽  
Ho Gene

ABSTRACT The two mating types of the yeast Saccharomyces cerevisiae can be interconverted in both homothallic and heterothallic strains. Previous work indicates that all yeast cells contain the information to be both a and α and that the HO gene (in homothallic strains) promotes a change in mating type by causing a change at the mating type locus itself. In both heterothallic and homothallic strains, a defective α mating type locus can be converted to a functional a locus and subsequently to a functional α locus. In contrast, action of the HO gene does not restore mating ability to a strain defective in another gene for mating which is not at the mating type locus. These observations indicate that a yeast cell contains an additional copy (or copies) of α information, and lead to the "cassette" model for mating type interconversion. In this model, HM  a and hmα loci are blocs of unexpressed α regulatory information, and HMα and hm  a loci are blocs of unexpressed a regulatory information. These blocs are silent because they lack an essential site for expression, and become active upon insertion of this information (or a copy of the information) into the mating type locus by action of the HO gene.

Identification of sequence elements that confer cell-type-specific control of MF alpha 1 expression in Saccharomyces cerevisiae

1987 ◽  
Vol 7 (9) ◽  
pp. 3185-3193
Author(s):  
K Inokuchi ◽  
A Nakayama ◽  
F Hishinuma
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Mating Type ◽  
Specific Gene ◽  
Cell Type ◽  
Coding Region ◽  
Transcription Start ◽  
Specific Expression ◽  
Type Locus ◽  
Mating Type Locus ◽  
Cell Type Specific

The MF alpha 1 gene of Saccharomyces cerevisiae, a major structural gene for mating pheromone alpha factor, is an alpha-specific gene whose expression is regulated by the mating-type locus. To study the role of sequences upstream of MF alpha 1 in its expression and regulation, we generated two sets of promoter deletions: upstream deletions and internal deletions. By analyzing these deletions, we have identified a TATA box and two closely related, tandemly arranged upstream activation sites as necessary elements for MF alpha 1 expression. Two upstream activation sites were located ca. 300 and 250 base pairs upstream of the MF alpha 1 transcription start points, which were also determined in this study. Each site contained a homologous 22-base-pair sequence, and both sites were required for maximum transcription level. The distance between the upstream activation sites and the transcription start points could be altered without causing loss of transcription efficiency, and the sites were active in either orientation with respect to the coding region. These elements conferred cell type-specific expression on a heterologous promoter. Analysis with host mating-type locus mutants indicates that these sequences are the sites through which the MAT alpha 1 product exerts its action to activate the MF alpha 1 gene. Homologous sequences with these elements were found in other alpha-specific genes, MF alpha 2 and STE3, and may mediate activation of this set of genes by MAT alpha 1.

scholarly journals LINKAGE OF MUTATIONS AFFECTING MINUS FLAGELLAR MEMBRANE AGGLUTINABILITY TO THE mt  - MATING-TYPE LOCUS OF CHLAMYDOMONAS

Genetics ◽  
1981 ◽  
Vol 99 (1) ◽  
pp. 41-47 ◽  
Author(s):  
Carol J Hwang ◽  
Brian C Monk ◽  
Ursula W Goodenough
Keyword(s):  
Uv Irradiation ◽  
Mating Type ◽  
Zygote Formation ◽  
Wild Type ◽  
Tetrad Analysis ◽  
Type Locus ◽  
Mating Type Locus ◽  
Flagellar Membrane ◽  
Mutant Strains

ABSTRACT Two independently isolated mutant strains, imp-10 and imp-12, were obtained by UV irradiation of wild-type mating-type minus (wt-). Each fails to agglutinate sexually with gametes of either mating type, but mating and zygote formation can be elicited by agglutinating either strain to wt+ gametes by means of anti-flagellar antiserum. Tetrad analysis of the resultant zygotes shows that both imp-10 and imp-12 are very closely linked to mt  -, with no recombinants observed. Diploid strains constructed between imp-10 or imp-12 and wt+ gametes are wt-, that is, they agglutinate and fuse like normal minus cells. Tetrad analysis of triploids from imp-10 diploid x wt+ haploid crosses shows that only imp-10 and wt+ products are recovered. A model is proposed to account for these results.

scholarly journals A SUPPRESSOR OF MATING-TYPE LOCUS MUTATIONS IN SACCHAROMYCES CEREVISIAE: EVIDENCE FOR AND IDENTIFICATION OF CRYPTIC MATING-TYPE LOCI

Genetics ◽  
1979 ◽  
Vol 93 (4) ◽  
pp. 877-901 ◽  
Author(s):  
Jasper Rine ◽  
Jeffrey N Strathern ◽  
James B Hicks ◽  
Ira Herskowitz
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Mating Type ◽  
Mating Types ◽  
Type Locus ◽  
Mating Ability ◽  
Mating Type Locus ◽  
A Cells

ABSTRACT A mutation has been identified that suppresses the mating and sporulation defects of all mutations in the mating-type loci of S. cereuisiae. This suppressor, sir1-1, restores mating ability to matαl and matα2 mutants and restores sporulation ability to matα2 and mata1 mutants. MATa sir1-1 strains exhibit a polar budding pattern and have reduced sensitivity to α-factor, both properties of a/α diploids. Furthermore, sir1-1 allows MATa/MATa, matα1/matα1, and MATα/MATα strains to sporulate efficiently. All actions of sir1-1 are recessive to SIR1. The ability of sir1-1 to supply all functions necessary for mating and sporulation and its effects in a cells are explained by proposing that sir1-1 allows expression of mating type loci which are ordinarily not expressed. The ability of sir1-1 to suppress the matαl-5 mutation is dependent on the HMa gene, previously identified as required for switching of mating types from a to α. Thus, as predicted by the cassette model, HMa is functionally equivalent to MATα since it supplies functions of MATα. We propose that sir1-1 is defective in a function, Sir ("Silent-information regulator"), whose role may be to regulate expression of HMa and HMα.

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.

A transcriptional cascade governs entry into meiosis in Saccharomyces cerevisiae

1989 ◽  
Vol 9 (5) ◽  
pp. 2142-2152
Author(s):  
H E Smith ◽  
A P Mitchell
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Mating Type ◽  
Meiotic Recombination ◽  
Deletion Mutant ◽  
Type Locus ◽  
Mating Type Locus ◽  
Recombination Pathway

Two signals activate meiosis in yeast: starvation and expression of the a1 and alpha 2 products of the mating-type locus. Prior studies suggest that these signals stimulate expression of an activator of meiosis, the IME1 (inducer of meiosis) product. We have cloned a gene, IME2, with properties similar to those of IME1: both genes are required for meiosis, and both RNAs are induced in meiotic cells. Elevated dosage of IME1 or IME2 stimulates the meiotic recombination pathway without starvation; thus, the IME products may be part of the switch that activates meiosis. IME1 was found to be required for IME2 expression, and a multicopy IME2 plasmid permitted meiosis in an ime1 deletion mutant. Accordingly, we propose that the IME1 product stimulates meiosis mainly through activation of IME2 expression.

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