Mating-type gene switching in a homothallic fission yeast

The Aα locus is one of four master regulatory loci that determine mating type and regulate sexual development in Schizophyllum commune. We have made a plasmid containing a URA1 gene disruption of the Aα Y1 gene. Y1 is the sole Aα gene in Aα1 strains. We used the plasmid construction to produce an Aα null (i.e., AαΔ) strain by replacing the genomic Y1 gene with URA1 in an Aα1 strain. To characterize the role of the Aα genes in the regulation of sexual development, we transformed various Aα Y and Z alleles into AαΔ strains and examined the acquired mating types and mating abilities of the transformants. These experiments demonstrate that the Aα Y gene is not essential for fungal viability and growth, that a solitary Z Aα mating-type gene does not itself activate development, that Aβ proteins are sufficient to activate the A developmental pathway in the absence of Aα proteins and confirm that Y and Z genes are the sole determinants of Aα mating type. The data from these experiments support and refine our model of the regulation of A-pathway events by Y and Z proteins.

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Schizosaccharomyces pombe ras1 and byr1 are functionally related genes of the ste family that affect starvation-induced transcription of mating-type genes.

Molecular and Cellular Biology ◽

10.1128/mcb.10.2.549 ◽

1990 ◽

Vol 10 (2) ◽

pp. 549-560 ◽

Cited By ~ 43

Author(s):

S A Nadin-Davis ◽

A Nasim

Keyword(s):

Gene Family ◽

Fission Yeast ◽

Mating Type ◽

Growth Cycle ◽

Yeast Cells ◽

Null Alleles ◽

Northern Analysis ◽

Gene Transcript ◽

Type Gene

We have further investigated the function of the ras1 and byr1 genes, which were previously shown to be critical for sexual differentiation in fission yeast cells. Several physiological similarities between strains containing null alleles of these genes supports the idea that ras1 and byr1 are functionally closely related. Furthermore, we have found that byr1 is allelic to ste1, one of at least 10 genes which when mutated can cause sterility. Since ras1 had previously been found to be allelic to ste5, both ras and byr genes are now clearly shown to be a part of the ste gene family, thus confirming their close functional relationship. The observation that the mating-type loci could overcome the sporulation block of ras1 and byr1 mutant strains prompted investigation of the role of the ras-byr pathway in the induction of the mating-type gene transcripts upon nitrogen starvation. By Northern analysis of RNA preparations from strains carrying wild-type or mutant ras1 alleles and grown to different stages of the growth cycle, we have shown that ras1 plays an important role in inducing the Pi transcript of the mating-type loci and the mei3 gene transcript. These observations provide a molecular basis for the role of the ste gene family, including ras1 and byr1, in meiosis and indicate that further characterization of other ste genes would be very useful for elucidating the mechanism of ras1 function in fission yeast cells.

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The sum1-1 mutation affects silent mating-type gene transcription in Saccharomyces cerevisiae.

Molecular and Cellular Biology ◽

10.1128/mcb.10.1.409 ◽

1990 ◽

Vol 10 (1) ◽

pp. 409-412 ◽

Cited By ~ 12

Author(s):

G P Livi ◽

J B Hicks ◽

A J Klar

Keyword(s):

Saccharomyces Cerevisiae ◽

Mating Type ◽

Transcriptional Control ◽

Gene Mutations ◽

State Level ◽

Mating Type Gene ◽

Gene Transcripts ◽

Mating Type Genes ◽

Type Gene ◽

Type Information

The silent mating-type genes (HML and HMR) of Saccharomyces cerevisiae are kept under negative transcriptional control by the trans-acting products of the four MAR/SIR loci. MAR/SIR gene mutations result in the simultaneous derepression of HML and HMR gene expression. The sum1-1 mutation was previously identified as an extragenic suppressor of mutations in MAR1 (SIR2) and MAR2 (SIR3). As assayed genetically, sum1-1 is capable of restoring repression of silent mating-type information in cells containing mar1 or mar2 null mutations. We show here that the mating-type phenotype associated with sum1-1 results from a dramatic reduction in the steady-state level of HML and HMR gene transcripts. At the same time, the sum1-1 mutation has no significant effect on the level of each of the four MAR/SIR mRNAs.

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Schizosaccharomyces pombe ras1 and byr1 are functionally related genes of the ste family that affect starvation-induced transcription of mating-type genes

Molecular and Cellular Biology ◽

10.1128/mcb.10.2.549-560.1990 ◽

1990 ◽

Vol 10 (2) ◽

pp. 549-560

Author(s):

S A Nadin-Davis ◽

A Nasim

Keyword(s):

Gene Family ◽

Fission Yeast ◽

Mating Type ◽

Growth Cycle ◽

Yeast Cells ◽

Null Alleles ◽

Northern Analysis ◽

Gene Transcript ◽

Type Gene

We have further investigated the function of the ras1 and byr1 genes, which were previously shown to be critical for sexual differentiation in fission yeast cells. Several physiological similarities between strains containing null alleles of these genes supports the idea that ras1 and byr1 are functionally closely related. Furthermore, we have found that byr1 is allelic to ste1, one of at least 10 genes which when mutated can cause sterility. Since ras1 had previously been found to be allelic to ste5, both ras and byr genes are now clearly shown to be a part of the ste gene family, thus confirming their close functional relationship. The observation that the mating-type loci could overcome the sporulation block of ras1 and byr1 mutant strains prompted investigation of the role of the ras-byr pathway in the induction of the mating-type gene transcripts upon nitrogen starvation. By Northern analysis of RNA preparations from strains carrying wild-type or mutant ras1 alleles and grown to different stages of the growth cycle, we have shown that ras1 plays an important role in inducing the Pi transcript of the mating-type loci and the mei3 gene transcript. These observations provide a molecular basis for the role of the ste gene family, including ras1 and byr1, in meiosis and indicate that further characterization of other ste genes would be very useful for elucidating the mechanism of ras1 function in fission yeast cells.

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