MUTATIONS OF THE a MATING-TYPE GENE IN NEUROSPORA CRASSA

Genetics ◽  
1978 ◽  
Vol 88 (2) ◽  
pp. 239-254 ◽  
Author(s):  
A J F Griffiths ◽  
A M DeLange
Keyword(s):  
Mating Type ◽  
Mutational Analysis ◽  
Chromosome 1 ◽  
Selection System ◽  
Type Locus ◽  
Heterokaryon Incompatibility ◽  
Mating Type Locus ◽  
Mating Type Gene ◽  
Type Gene ◽  
Restoration Of Fertility

ABSTRACT In Neurospora, the mating-type locus controls both mating (A + a is fertile) and heterokaryosis (A + a is incompatible). The two alleles appear stable: no novel fertility reactions have ever been reported, and attempts to separate fertility and heterokaryon incompatibility functions by recombination have been unsuccessful. In the present approach the locus was studied through a mutational analysis of heterokaryon incompatibility function. A selection system was used that detects vigorous (A + a) heterokaryotic colonies against a background of inhibited growth. Twenty-five mutants of an a strain were produced following mutagenic treatment with UV and NG: 15 were viable as homokaryons and 10 were not. All but one were infertile, but most showed an abortive mating reaction involving the production of barren, well-developed perithecia with A and (surprisingly) a testers. None of the mutants complement each other to restore fertility. Seven mutants have been mapped to the mating-type locus region of chromosome 1. Restoration of fertility was used to detect revertants, and these were found in five out of the eight mutants tested. (A dose response was observed). In four cases incompatibility was fully restored and in one case it was not.—The results suggest two positive actions of the locus when in heterozygous (A/a) combination (the stimulation of some stage of ascus production and the inhibition of vegetative heterokaryosis), and one positive action in homozygous combination (the production of a perithecial inhibitor).

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

Genetics ◽  
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.

ESCAPE FROM MATING-TYPE INCOMPATIBILITY IN BISEXUAL (A + a) NEUROSPORA HETEROKARYONS

1975 ◽  
Vol 17 (3) ◽  
pp. 441-449 ◽  
Author(s):  
A. M. DeLange ◽  
A. J. F. Griffiths
Keyword(s):  
Mating Type ◽  
Loss Of Function ◽  
Wild Type ◽  
Opposite Mating Type ◽  
Type Locus ◽  
Heterokaryon Incompatibility ◽  
Recessive Mutant ◽  
Type Rate ◽  
Wild Type Rate ◽  
Incompatibility Locus

In Neurospora crassa, strains of opposite mating type generally do not form stable heterokaryons because the mating type locus acts as a heterokaryon incompatibility locus. However, when one A and one a strain, having complementing auxotrophic mutants, are placed together on minimal medium, growth may occur, although the growth is generally slow. In this study, escape from such slow growth to that at a wild type or near-wild type rate was observed. The escaped cultures are stable heterokaryons, mostly having lost the mating type allele function from one component nucleus, so that the nuclear types are heterokaryon compatible. Either A or a mating type can be lost. This loss of function has been attributed to deletion since only one nuclear type could be recovered in all heterokaryons except one, but deletion spanning adjacent loci has been directly demonstrated in a minority of cases. Alternatively when one component strain is tol and the other tol+ (tol being a recessive mutant suppressing the heterokaryon incompatibility associated with mating type), escape may occur by the deletion or mutation of tol+, also resulting in heterokaryon compatibility. An induction mechanism for escape is speculated upon.

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.

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

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.

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.

Sign in / Sign up

Export Citation Format

Share Document