Sexual conjugation in yeast. Cell surface changes in response to the action of mating hormones.

In the yeast Saccharomyces cerevisiae, sexual conjugation between haploid cells of opposite mating type results in the formation of a diploid zygote. When treated with fluorescently labeled concanavalin A, a zygote stains nonuniformly, with the greatest fluorescence occurring at the conjugation bridge between the two haploid parents. In the mating mixture, unconjugated haploid cells often elongate to pear-shaped forms ("shmoos") which likewise exhibit asymmetric staining with the most intense fluorescence at the growing end. Shmoo formation can be induced in cells of one mating type by the addition of a hormone secreted by cells of the opposite mating type; such shmoos also stain asymmetrically. In nearly all cases, the nonmating mutants that were examined stained uniformly after incubation with the appropriate hormone. Asymmetric staining is not observed with vegetative cells, even those that are budded. These results suggest that, before and during conjugation, localized cell surface changes occur in cells of both mating types; the surface alterations facilitate fusion and are apparently mediated by the hormones in a manner that is mating-type specific.

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

Genetics ◽

10.1093/genetics/85.3.373 ◽

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.

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Localized secretion of acid phosphatase reflects the pattern of cell surface growth in saccharomyces cerevisiae

The Journal of Cell Biology ◽

10.1083/jcb.86.1.123 ◽

1980 ◽

Vol 86 (1) ◽

pp. 123-128 ◽

Cited By ~ 92

Author(s):

C Field ◽

R Schekman

Keyword(s):

Saccharomyces Cerevisiae ◽

Acid Phosphatase ◽

Cell Surface ◽

Mating Type ◽

Surface Growth ◽

Parent Cell ◽

Limited Growth ◽

Yeast Cell Surface ◽

Dividing Cells ◽

A Cell

Secretion of cell wall-bound acid phosphatase by Saccharomyces cerevisiae occurs along a restricted portion of the cell surface. Acid phosphatase activity produced during derepressed synthesis on a phosphate-limited growth medium is detected with an enzyme-specific stain and is localized initially to the bud portion of a dividing cell. After two to three generations of phosphate-limited growth, most of the cells can be stained; if further phosphatase synthesis is repressed by growth in excess phosphate, dividing cells are produced in which the parent but not the bud can be stained. Budding growth is interrupted in α-mating-type cells by a pheromone (α-factor) secreted by the opposite mating type; cell surface growth continues in the presence of α-factor and produces a characteristic cell tip. When acid phosphatase synthesis is initiated during α-factor treatment, only the cell tip can br stained; when phosphate synthesis is repressed during α-factor treatment, the cell body but not the tip can be stained. A mixture of derepressed α cells and phosphatase-negative α cells form zygotes in which mainly one parent cell surface can be stained. The cell cycle mutant, cdc 24 (Hartwell, L.H. 1971. Exp. Cell Res. 69:265-276), fails to bud and, instead, expands symmetrically as a sphere at a nonpermissive temperature (37 degrees C). This mutant does not form a cell tip during α-factor treatment at 37 degrees C, and although acid phosphatade secretion occurs at this temperature, it is not localized. These results suggest that secretion reflects a polar mode of yeast cell- surface growth, and that this organization requires the cdc 24 gene product.

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Post-Transcriptional Control of Mating-Type Gene Expression during Gametogenesis in Saccharomyces cerevisiae

Biomolecules ◽

10.3390/biom11081223 ◽

2021 ◽

Vol 11 (8) ◽

pp. 1223

Author(s):

Randi Yeager ◽

G. Guy Bushkin ◽

Emily Singer ◽

Rui Fu ◽

Benjamin Cooperman ◽

...

Keyword(s):

Gene Expression ◽

Saccharomyces Cerevisiae ◽

Mating Type ◽

Transcriptional Control ◽

Regulation Of Gene Expression ◽

Mating Types ◽

Yeast Saccharomyces Cerevisiae ◽

Type Gene ◽

Diploid Cells ◽

Retained Introns

Gametogenesis in diploid cells of the budding yeast Saccharomyces cerevisiae produces four haploid meiotic products called spores. Spores are dormant until nutrients trigger germination, when they bud asexually or mate to return to the diploid state. Each sporulating diploid produces a mix of spores of two haploid mating types, a and α. In asexually dividing haploids, the mating types result from distinct, mutually exclusive gene expression programs responsible for production of mating pheromones and the receptors to sense them, all of which are silent in diploids. It was assumed that spores only transcribe haploid- and mating-type-specific genes upon germination. We find that dormant spores of each mating type harbor transcripts representing all these genes, with the exception of Mata1, which we found to be enriched in a spores. Mata1 transcripts, from a rare yeast gene with two introns, were mostly unspliced. If the retained introns reflect tethering to the MATa locus, this could provide a mechanism for biased inheritance. Translation of pheromones and receptors were repressed at least until germination. We find antisense transcripts to many mating genes that may be responsible. These findings add to the growing number of examples of post-transcriptional regulation of gene expression during gametogenesis.

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Appearance of virus-specific RNA, virus particles, and cell surface changes in cells rapidly transformed by the murine sarcoma virus

Virology ◽

10.1016/0042-6822(73)90477-7 ◽

1973 ◽

Vol 53 (1) ◽

pp. 186-195 ◽

Cited By ~ 25

Author(s):

Samuel Salzberg ◽

Martin S. Robin ◽

Maurice Green

Keyword(s):

Cell Surface ◽

Rna Virus ◽

Virus Particles ◽

Murine Sarcoma Virus ◽

Sarcoma Virus ◽

Cell Surface Changes ◽

Murine Sarcoma ◽

Surface Changes ◽

In Cells

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Fungal fimbriae. II. Their role in conjugation in Ustilago violacea

Canadian Journal of Microbiology ◽

10.1139/m75-077 ◽

1975 ◽

Vol 21 (4) ◽

pp. 547-557 ◽

Cited By ~ 23

Author(s):

A. W. Day ◽

N. H. Poon

Keyword(s):

Cell Surface ◽

Mating Type ◽

Electron Micrographs ◽

Essential Role ◽

Smut Fungus ◽

Mating Types ◽

Opposite Mating Type ◽

Sensitive Material ◽

Ustilago Violacea ◽

Anther Smut

During conjugation in the anther smut fungus Ustilago violacea cells of opposite mating type first pair tightly and then develop a conjugation tube or bridge between them. The cells of both mating types are covered in long fine hairs or fimbriae, some of which appear to end in knobs. Experiments involving enzyme treatments of the cell surface indicate that these fimbriae do not play an essential role in cell pairing, instead pairing seems to be initiated when one or both mating types produce amorphous masses of α-amylase-sensitive material. Electron micrographs, enzyme and inhibitor studies, and experiments using restrictive temperatures suggest, however, that fimbriae may be essential for the later stages of conjugation i.e. development of the conjugation tube. If so, it is suggested that they may permit the exchange of macromolecules between the conjugating cells, initiating localized wall-softening and wall-breakdown.

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A MUTATION ALLOWING EXPRESSION OF NORMALLY SILENT a MATING-TYPE INFORMATION IN SACCHAROMYCES CEREVISIAE

Genetics ◽

10.1093/genetics/104.2.219 ◽

1983 ◽

Vol 104 (2) ◽

pp. 219-234

Author(s):

Harry Gruenspan ◽

Norman R Eaton

Keyword(s):

Saccharomyces Cerevisiae ◽

Mating Type ◽

Constitutive Expression ◽

Mating Types ◽

Regulatory Mutation ◽

Dominant Mutation ◽

Yeast Saccharomyces Cerevisiae ◽

Cis Acting ◽

A Cells ◽

Type Information

ABSTRACT Mating type in haploid cells of the yeast Saccharomyces cerevisiae is determined by a pair of alleles MAT a and MATα. Under various conditions haploid mating types can be interconverted. It has been proposed that transpositions of silent cassettes of mating-type information from HML or HMR to MAT are the source of mating type conversions. A mutation described in this work, designated AON1, has the following properties. (1) MATα cells carring AON1 are defective in mating. (2) AON1 allows MATα/MATα but not MAT a/MAT a diploids to sporulate; thus, AON1 mimics the MAT a requirement for sporulation. (3) mat a-1 cells that carry AON1 are MAT a phenocopies, i.e., MATα/mat a-1 AON1 diploids behave as standard MATα/MAT a cells; therefore, AON1 suppresses the defect of mat a-1. (4) AON1 maps at or near HMR a. (5) Same-site revertants from AON1 lose the ability to convert mating type to MAT a, indicating that reversion is associated with the loss of a functional HMR a locus. In addition, AON1 is a dominant mutation. We conclude that AON1 is a regulatory mutation, probably cis-acting, that leads to the constitutive expression of silent a mating-type information located at HMR a.

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Cloning and characterization of four SIR genes of Saccharomyces cerevisiae.

Molecular and Cellular Biology ◽

10.1128/mcb.6.2.688 ◽

1986 ◽

Vol 6 (2) ◽

pp. 688-702 ◽

Cited By ~ 144

Author(s):

J M Ivy ◽

A J Klar ◽

J B Hicks

Keyword(s):

Saccharomyces Cerevisiae ◽

Mating Type ◽

Blot Analysis ◽

Transcriptional Control ◽

Genomic Library ◽

Yeast Saccharomyces Cerevisiae ◽

Mating Type Genes ◽

Rna Blots

Mating type in the yeast Saccharomyces cerevisiae is determined by the MAT (a or alpha) locus. HML and HMR, which usually contain copies of alpha and a mating type information, respectively, serve as donors in mating type interconversion and are under negative transcriptional control. Four trans-acting SIR (silent information regulator) loci are required for repression of transcription. A defect in any SIR gene results in expression of both HML and HMR. The four SIR genes were isolated from a genomic library by complementation of sir mutations in vivo. DNA blot analysis suggests that the four SIR genes share no sequence homology. RNA blots indicate that SIR2, SIR3, and SIR4 each encode one transcript and that SIR1 encodes two transcripts. Null mutations, made by replacement of the normal genomic allele with deletion-insertion mutations created in the cloned SIR genes, have a Sir- phenotype and are viable. Using the cloned genes, we showed that SIR3 at a high copy number is able to suppress mutations of SIR4. RNA blot analysis suggests that this suppression is not due to transcriptional regulation of SIR3 by SIR4; nor does any SIR4 gene transcriptionally regulate another SIR gene. Interestingly, a truncated SIR4 gene disrupts regulation of the silent mating type loci. We propose that interaction of at least the SIR3 and SIR4 gene products is involved in regulation of the silent mating type genes.

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