BEHAVIOUR OF NEUROSPORA TETRASPERMA MATING-TYPE GENES INTROGRESSED INTO N. CRASSA

Abstract Using genomic subtraction, we isolated the mating-type genes (Mat1-1 and Mat1-2) of the rice blast fungus, Magnaporthe grisea. Transformation of M. grisea strains of one mating type with a linearized cosmid clone carrying the opposite mating-type gene resulted in many "dual maters," strains that contain both mating-type genes and successfully mate with Mat1-1 and Mat1-2 testers. Dual maters differed in the frequency of production of perithecia in pure culture. Ascospores isolated from these homothallic crosses were either Mat1-1 or Mat1-2, but there were no dual maters. Most conidia from dual maters also had one or the other of the mating-type genes, but not both. Thus, dual maters appear to lose one of the mating-type genes during vegetative growth. The incidence of self-mating in dual maters appears to depend on the co-occurrence of strains with each mating type in vegetative cultures. In rare transformants, the incoming sequences had replaced the resident mating-type gene. Nearly isogenic pairs produced from three M. grisea laboratory strains were mated to investigate their fertility. One transformant with switched mating type appears to have a mutation that impairs the development of asci when its mating partner has a similar genetic background. The M. grisea Mat1-1 and Mat1-2 genes are idiomorphs approximately 2.5 and 3.5 kb in length, respectively.

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Deletion of the Schizophyllum commune Aα Locus: The Roles of Aα Y and Z Mating-Type Genes

Genetics ◽

10.1093/genetics/144.4.1437 ◽

1996 ◽

Vol 144 (4) ◽

pp. 1437-1444

Author(s):

C Ian Robertson ◽

Kirk A Bartholomew ◽

Charles P Novotny ◽

Robert C Ullrich

Keyword(s):

Mating Type ◽

Sexual Development ◽

Schizophyllum Commune ◽

Mating Types ◽

Developmental Pathway ◽

Mating Type Gene ◽

Mating Type Genes ◽

Regulatory Loci ◽

Type Gene

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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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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MATING-TYPE MUTATIONS IN SCHIZOSACCHAROMYCES POMBE: ISOLATION OF MUTANTS AND ANALYSIS OF STRAINS WITH AN h - or h + PHENOTYPE

Genetics ◽

10.1093/genetics/83.2.259 ◽

1976 ◽

Vol 83 (2) ◽

pp. 259-273

Author(s):

James H Meade ◽

Herbert Gutz

Keyword(s):

Schizosaccharomyces Pombe ◽

Gene Product ◽

Mating Type ◽

Sexual Cycle ◽

Type Region ◽

Type Allele ◽

Mating Type Gene ◽

Auxiliary Gene ◽

Type Gene

ABSTRACT Mutants defective in various steps of the sexual cycle have been isolated from homothallic strains of Schizosaccharomyces pombe by Bresch, Müller and Egel (1968). These mutants include heterothallic h + and h - strains. We have isolated additional h + and h -mutants from homothallic strains. Those mutants which are due to mutations in the mating-type region were analyzed in detail. Our results show that the mating-type gene mat2 not only has a function in copulation and meiosis, but that it also regulates the formation of the map1 gene product (map1 is a mating-type auxiliary gene). Some of the h - mutants have lost only one of the three functions while others are defective in at least two, and perhaps all three, functions. Further, we show that the mat1 - allele of h90 strains can mutate to mat1 + but that mutations in mat2 appear to affect the mutational behavior of mat1. Finally, we describe a new inactive mating-type allele, mat2*, which is different from mat2 0 in that it can mutate to mat2 +.

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

Molecular and Cellular Biology ◽

10.1128/mcb.10.1.409-412.1990 ◽

1990 ◽

Vol 10 (1) ◽

pp. 409-412

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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Structure and function of mating type genes in Cochliobolus spp. and asexual fungi

Canadian Journal of Botany ◽

10.1139/b95-322 ◽

1995 ◽

Vol 73 (S1) ◽

pp. 778-783 ◽

Cited By ~ 19

Author(s):

B. Gillian Turgeon ◽

Amir Sharon ◽

Stefan Wirsel ◽

Kenichi Yamaguchi ◽

Solveig K. Christiansen ◽

...

Keyword(s):

Mating Type ◽

Opposite Mating Type ◽

Asexual Fungi ◽

Mating Type Genes ◽

Type Gene ◽

And Function ◽

Mat Locus ◽

Mat Genes ◽

Mat Gene ◽

Transgenic Strains

Mating type (MAT) genes of Cochliobolus heterostrophus have homologs in other heterothallic Cochliobolus spp., in homothallic Cochliobolus spp., and in asexual fungi thought to be taxonomically related to Cochliobolus (e.g., Bipolaris spp.). To examine the cause of asexuality in B. sacchari, its homolog of C. heterostrophus MAT-2 was cloned. The B. sacchari sequence was 98% identical to that of C. heterostrophus MAT-2, the gene conferred homothallism when expressed in a C. heterostrophus MAT-1 strain, and transgenic strains mated with C. heterostrophus MAT-1. Thus the cause of asexuality in B. sacchari is not absence or lack of a functional MAT gene. When the C. heterostrophus MAT genes were expressed in B. sacchari, however, no sexual development occurred, suggesting that this asexual fungus lacks an attribute, other than the mating type gene, which is required for mating. Although cloned MAT genes function upon transformation into recipient strains, they do not confer full fertility. When an homologous or heterologous (e.g., from C. carbonum, C. victoriae, or B. sacchari) MAT gene is transferred into a C. heterostrophus strain of opposite mating type, the strain can self and cross to tester strains of either mating type. However, any transgenic strain carrying both a resident MAT gene and an homologous or heterologous MAT transgene develops normal perithecia but few ascospores in a cross that requires function of the transgene. To determine if the resident MAT gene interferes with function of the transgene, the MAT locus was deleted from the genome of C. heterostrophus and then replaced with the MAT gene of C. heterostrophus, C. carbonum, C. victoriae, or B. sacchari. Interference was eliminated and abundant ascospores were formed when the four transgenic strains were crossed to C. heterostrophus strains of opposite mating type. Key words: asexual fungi, DNA-binding proteins, heterologous expression, transformation.

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Homothallic switching of Saccharomyces cerevisiae mating type genes by using a donor containing a large internal deletion

Molecular and Cellular Biology ◽

10.1128/mcb.5.8.2154-2158.1985 ◽

1985 ◽

Vol 5 (8) ◽

pp. 2154-2158

Author(s):

B Weiffenbach ◽

J E Haber

Keyword(s):

Saccharomyces Cerevisiae ◽

Gene Conversion ◽

Mating Type ◽

Gene Conversion Event ◽

Conversion Event ◽

Base Pair Deletion ◽

Mating Type Genes ◽

Type Gene ◽

Mat Locus ◽

Donor Locus

Homothallic switching of the mating type genes of Saccharomyces cerevisiae occurs by a gene conversion event, replacing sequences at the expressed MAT locus with a DNA segment copied from one of two unexpressed loci, HML or HMR. The transposed Ya or Y alpha sequences are flanked by homologous regions that are believed to be essential for switching. We examined the transposition of a mating type gene (hmr alpha 1-delta 6) which contains a 150-base-pair deletion spanning the site where the HO endonuclease generates a double-stranded break in MAT that initiates the gene conversion event. Despite the fact that the ends of the cut MAT region no longer share homology with the donor hmr alpha 1-delta 6, switching of MATa or MAT alpha to mat alpha 1-delta 6 was efficient. However, there was a marked increase in the number of aberrant events, especially the formation of haploid-inviable fusions between MAT and the hmr alpha 1-delta 6 donor locus.

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