Apothecial development and sexuality in Ascobolus sacchariferus

1976 ◽  
Vol 54 (15) ◽  
pp. 1784-1792
Author(s):  
John W. Paden ◽  
M. A. Susan Linton
Keyword(s):  
Mating Type ◽  
Opposite Mating Type ◽  
Negative Results ◽  
Compatible Cross ◽  
Incompatible Cross ◽  
Vegetative Propagules

Sexuality and apothecial ontogeny in the operculate Discomycete Ascobolus sacchariferus (Ascomycetes, Pezizales) were investigated. Ascobolus sacchariferus is heterothallic and produces oidia that can function as vegetative propagules or as gametes. When oidia are contrasted with mycelia in either a compatible or incompatible cross, they fail to germinate. In a compatible cross the oidia are changed physiologically into functional antheridia and attract hyphae of the opposite mating type, which then delimit ascogonia. The ascogonia are blunt-ended, without a differentiated trichogyne, and coil around the oidia. Some strains were found to be stronger males, others stronger females. After plasmogamy, apothecial development is cleistohymenial. Opening of most apothecia occurs in the midmesohymenial phase. After opening, ripe asci protrude from the hymenial surface. Attempts to hybridize A. sacchariferus and A. sterocorarius yielded negative results. The two species, however, inhibit the germination of each other's oidia.

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.

Pycnial nectar of rust fungi induces cap formation on pycniospores of opposite mating type

Mycologia ◽  
1999 ◽  
Vol 91 (5) ◽  
pp. 858-870 ◽  
Author(s):  
Y. Anikster ◽  
T. Eilam ◽  
L. Mittelman ◽  
L.J. Szabo ◽  
W. R. Bushnell
Keyword(s):  
Mating Type ◽  
Rust Fungi ◽  
Opposite Mating Type

POOR FRUITERS AND BARRAGE MUTANTS IN GELASINOSPORA

1956 ◽  
Vol 34 (2) ◽  
pp. 231-240 ◽  
Author(s):  
E. Silver Dowding ◽  
A. Bakerspigel
Keyword(s):  
Growth Rate ◽  
Mating Type ◽  
Opposite Mating Type ◽  
Nutritional Factors ◽  
Wild Strains ◽  
Hyphal Tip

Anomalous sterility and slow fruiting occur among the following types of cultures: (1) mated homokaryotic mycelia grown from dwarf ascospores; (2) heterokaryotic mycelia grown from normal-sized ascospores; (3) hyphal-tip cultures from heterokaryotic mycelia. Such behavior may be caused by a mutant nucleus whose nutritional factors do not complement those in the nuclei of opposite mating type. Among the sterile and slow-fruiting strains were found 'barrage' mutants. They differ in texture and growth rate from wild strains. When grown in pairs, their hyphac, as they approach each other, exhibit aversion or barrage. Progeny of mated barrage strains are likewise barrage strains.

scholarly journals Isolation and genetic analysis of Saccharomyces cerevisiae mutants supersensitive to G1 arrest by a factor and alpha factor pheromones.

1982 ◽  
Vol 2 (1) ◽  
pp. 11-20 ◽  
Author(s):  
R K Chan ◽  
C A Otte
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Mating Type ◽  
Solid Medium ◽  
G1 Arrest ◽  
Alpha Cells ◽  
Opposite Mating Type ◽  
Alpha Factor ◽  
Complementation Groups ◽  
Chromosome Iii ◽  
The Right

Eight independently isolated mutants which are supersensitive (Sst-) to the G1 arrest induced by the tridecapeptide pheromone alpha factor were identified by screening mutagenized Saccharomyces cerevisiae MATa cells on solid medium for increased growth inhibition by alpha factor. These mutants carried lesions in two complementation groups, sst1 and sst2. Mutations at the sst1 locus were mating type specific: MATa sst1 cells were supersensitive to alpha factor, but MAT alpha sst1 cells were not supersensitive to a factor. In contrast, mutations at the sst2 locus conferred supersensitivity to the pheromones of the opposite mating type on both MATa and MAT alpha cells. Even in the absence of added alpha pheromone, about 10% of the cells in exponentially growing cultures of MATa strains carrying any of three different alleles of sst2 (including the ochre mutation sst2-4) had the aberrant morphology ("shmoo" shape) that normally develops only after MATa cells are exposed to alpha factor. This "self-shmooing" phenotype was genetically linked to the sst2 mutations, although the leakiest allele isolated (sst2-3) did not display this characteristic. Normal MATa/MAT alpha diploids do not respond to pheromones; diploids homozygous for an sst2 mutation (MATa/MAT alpha sst2-1/sst2-1) were still insensitive to alpha factor. The sst1 gene was mapped to within 6.9 centimorgans of his6 on chromosome IX. The sst2 gene was unlinked to sst1, was not centromere linked, and was shown to be neither linked to nor centromere distal to MAT on the right arm of chromosome III.

Selection for mating competence in Magnaporthe grisea pathogenic to rice

1991 ◽  
Vol 69 (10) ◽  
pp. 2130-2134 ◽  
Author(s):  
Chih-Cheng T. Chao ◽  
Albert H. Ellingboe
Keyword(s):  
Key Words ◽  
Mating Type ◽  
Rice Blast ◽  
Magnaporthe Grisea ◽  
Opposite Mating Type ◽  
Selection For ◽  
Sib Selection ◽  
Selection Of

Sib selection for mating competence among isolates of Magnaporthe grisea that are pathogenic on rice has led to the selection of isolates where the mating type alleles are the only restriction on mating competence. Isolates are able to mate with all sibling isolates of opposite mating type and produce asci with ascospores. Isolates can function as male, female, or hermaphrodite in mating depending on the isolates with which they are mated. Mating competence is controlled by the genes in both mated isolates. Key words: mating competence, sib selection, rice blast, genetics.

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 Temporal Genetic Dynamics of an Experimental, Biparental Field Population of Phytophthora capsici

2016 ◽  
Author(s):  
Maryn O. Carlson ◽  
Elodie Gazave ◽  
Michael A. Gore ◽  
Christine D. Smart
Keyword(s):  
Mating Type ◽  
Phytophthora Capsici ◽  
Haplotype Frequency ◽  
Experimental System ◽  
Experimental Population ◽  
Evolutionary Potential ◽  
Opposite Mating Type ◽  
Generational Shift ◽  
Frequency Changes ◽  
Pathogen Populations

AbstractDefining the contributions of dispersal, reproductive mode, and mating system to the population structure of a pathogenic organism is essential to estimating its evolutionary potential. After introduction of the devastating plant pathogen, Phytophthora capsici, into a grower’s field, a lack of aerial spore dispersal restricts migration. Once established, coexistence of both mating types results in formation of overwintering recombinant oospores, engendering persistent pathogen populations. To mimic these conditions, in 2008, we inoculated a field with two P. capsici isolates of opposite mating type. We analyzed pathogenic isolates collected in 2009-13 from this experimental population, using genome-wide single-nucleotide polymorphism markers. By tracking heterozygosity across years, we show that the population underwent a generational shift; transitioning from exclusively F1 in 2009-10; mixed generational in 2011; and ultimately all inbred in 2012-13. Survival of F1 oospores, characterized by heterozygosity excess, coupled with a low rate of selfing, delayed declines in heterozygosity due to inbreeding and attainment of equilibrium genotypic frequencies. Large allele and haplotype frequency changes in specific genomic regions accompanied the generational shift, representing putative signatures of selection. Finally, we identified an approximately 1.6 Mb region associated with mating type determination, constituting the first detailed genomic analysis of a mating type region (MTR) in Phytophthora. Segregation patterns in the MTR exhibited tropes of sex-linkage, where maintenance of allele frequency differences between isolates of opposite mating type was associated with elevated heterozygosity despite inbreeding. Characterizing the trajectory of this experimental system provides key insights into the processes driving persistent, sexual pathogen populations.

Isolation and genetic analysis of Saccharomyces cerevisiae mutants supersensitive to G1 arrest by a factor and alpha factor pheromones

1982 ◽  
Vol 2 (1) ◽  
pp. 11-20
Author(s):  
R K Chan ◽  
C A Otte
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Mating Type ◽  
Solid Medium ◽  
G1 Arrest ◽  
Alpha Cells ◽  
Opposite Mating Type ◽  
Alpha Factor ◽  
Complementation Groups ◽  
Chromosome Iii ◽  
The Right

Eight independently isolated mutants which are supersensitive (Sst-) to the G1 arrest induced by the tridecapeptide pheromone alpha factor were identified by screening mutagenized Saccharomyces cerevisiae MATa cells on solid medium for increased growth inhibition by alpha factor. These mutants carried lesions in two complementation groups, sst1 and sst2. Mutations at the sst1 locus were mating type specific: MATa sst1 cells were supersensitive to alpha factor, but MAT alpha sst1 cells were not supersensitive to a factor. In contrast, mutations at the sst2 locus conferred supersensitivity to the pheromones of the opposite mating type on both MATa and MAT alpha cells. Even in the absence of added alpha pheromone, about 10% of the cells in exponentially growing cultures of MATa strains carrying any of three different alleles of sst2 (including the ochre mutation sst2-4) had the aberrant morphology ("shmoo" shape) that normally develops only after MATa cells are exposed to alpha factor. This "self-shmooing" phenotype was genetically linked to the sst2 mutations, although the leakiest allele isolated (sst2-3) did not display this characteristic. Normal MATa/MAT alpha diploids do not respond to pheromones; diploids homozygous for an sst2 mutation (MATa/MAT alpha sst2-1/sst2-1) were still insensitive to alpha factor. The sst1 gene was mapped to within 6.9 centimorgans of his6 on chromosome IX. The sst2 gene was unlinked to sst1, was not centromere linked, and was shown to be neither linked to nor centromere distal to MAT on the right arm of chromosome III.

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