A SUPPRESSOR OF THE HETEROKARYON- INCOMPATIBILITY ASSOCIATED WITH MATING TYPE IN NEUROSPORA CRASSA

1970 ◽  
Vol 12 (4) ◽  
pp. 914-926 ◽  
Author(s):  
Dorothy Newmeyer
Keyword(s):  
Linkage Group ◽  
Neurospora Crassa ◽  
Mating Type ◽  
Vegetative Growth ◽  
Mode Of Action ◽  
Wild Strain ◽  
Group Iv ◽  
Mating Types ◽  
Vegetative Incompatibility ◽  
Opposite Mating Type

Neurospora crassa strains of opposite mating type are ordinarily heterokaryon-incompatible during vegetative growth. An unlinked mutant called tolerant (tol) is described, which suppresses the vegetative incompatibility of unlike mating types without affecting their ability to cross. The mutant tol was selected and studied by means of duplications heterozygous for mating type. Use of the duplication eliminates complications due to unlinked heterokaryon genes. The mode of action of tol has been confirmed by conventional heterokaryon tests. tol has been mapped in linkage group IV, close to tryp-4. A suppressor similar or identical to tolerant has been found in a wild strain from Panama, out of 14 different wild types which were tested. By using a different duplication which covers the unlinked heterokaryon-compatibility locus C, it was shown that tolerant does not suppress C/c incompatibility. The fact that tolerant suppresses only one of the two functions ascribed to mating type revives the question of whether 'mating-type' is one gene or two. However, the data strongly support Pittenger's (1957) conclusion that, if two genes are involved, they must be closely linked.

NULL MUTANTS OF THE A AND a MATING TYPE ALLELES OF NEUROSPORA CRASSA

1982 ◽  
Vol 24 (2) ◽  
pp. 167-176 ◽  
Author(s):  
A. J. F. Griffiths
Keyword(s):  
Linkage Group ◽  
Neurospora Crassa ◽  
Uv Irradiation ◽  
Mating Type ◽  
Opposite Mating Type ◽  
Extended Study ◽  
Fundamental Properties ◽  
Group I ◽  
Sexual Compatibility ◽  
Null Mutants

Thirty-five null mutants have now been obtained of the A mating type allele, which have simultaneously lost both known functions-heterokaryon incompatibility and sexual compatibility with strains of the opposite mating type, a. The mutants, designated Am, were obtained by selecting for heterokaryon compatibility following UV-irradiation of the normal A. Twenty-five of the mutations were viable as homokaryons. Both functions reverted together when two of these were irradiated. In most respects, Am mutations resemble the previously reported am mutations in their behavior. The Am mutations differ, however, in failing to produce illegitimate empty perithecia in crosses with testers of the same mating type from which they originated. — The previously obtained am mutants were characterized further. It was confirmed that these am mutants show abortive mating reactions, legitimate and illegitimate, with several tester strains, thus showing that such reactions are fundamental properties of the mutants themselves. In support of this, it was shown that the A-like behavior of am strains in the illegitimate reaction is not due to acquisition of determining elements through cytoplasmic contact with A in heterokaryons. It is possible that the sterile am mutants can be carried through a cross by a fertile heterokaryotic partner, but an extended study of meiotic products presumed to stem from this process confirmed that if such a process occurs it can involve no recombination on linkage group I. The single fertile am mutant was shown to have normal recombination on L.G.I. Escape from (A + a) incompatibility was shown to be possible in the identical heterokaryon used for am induction. Escape cannot be ruled out as a source of nonrecoverable am mutations.

scholarly journals Pheromones Are Essential for Male Fertility and Sufficient To Direct Chemotropic Polarized Growth of Trichogynes during Mating in Neurospora crassa

2006 ◽  
Vol 5 (3) ◽  
pp. 544-554 ◽  
Author(s):  
Hyojeong Kim ◽  
Katherine A. Borkovich
Keyword(s):  
Neurospora Crassa ◽  
Mating Type ◽  
Male Fertility ◽  
Mate Recognition ◽  
Mating Types ◽  
Polarized Growth ◽  
Opposite Mating Type ◽  
Cognate Receptor ◽  
Female Specific ◽  
Self Stimulation

ABSTRACT Neurospora crassa is a self-sterile filamentous fungus with two mating types, mat A and mat a. Its mating involves chemotropic polarized growth of female-specific hyphae (trichogynes) toward male cells of the opposite mating type in a process involving pheromones and receptors. mat A cells express the ccg-4 pheromone and the pre-1 receptor, while mat a strains produce mRNA for the pheromone mfa-1 and the pre-2 receptor; MFA-1 and CCG-4 are the predicted ligands for PRE-1 and PRE-2, respectively. In this study, we generated Δccg-4 and Δmfa-1 mutants and engineered a mat a strain to coexpress ccg-4 and its receptor, pre-2. As males, Δccg-4 mat A and Δmfa-1 mat a mutants were unable to attract mat a and mat A trichogynes, respectively, and consequently failed to initiate fruiting body (perithecial) development or produce meiotic spores (ascospores). In contrast, Δccg-4 mat a and Δmfa-1 mat A mutants exhibited normal chemotropic attraction and male fertility. Δccg-4 Δmfa-1 double mutants displayed defective chemotropism and male sterility in both mating types. Heterologous expression of ccg-4 enabled mat a males to attract mat a trichogynes, although subsequent perithecial differentiation did not occur. Expression of ccg-4 and pre-2 in the same strain triggered self-stimulation, resulting in formation of barren perithecia with no ascospores. Our results indicate that CCG-4 and MFA-1 are required for mating-type-specific male fertility and that pheromones (and receptors) are initial determinants for sexual identity during mate recognition. Furthermore, a self-attraction signal can be transmitted within a strain that expresses a pheromone and its cognate receptor.

scholarly journals Molecular Characterization of tol, a Mediator of Mating-Type-Associated Vegetative Incompatibility in Neurospora crassa

Genetics ◽  
1999 ◽  
Vol 151 (2) ◽  
pp. 545-555 ◽  
Author(s):  
Patrick Ka Tai Shiu ◽  
N Louise Glass
Keyword(s):  
Sexual Reproduction ◽  
Neurospora Crassa ◽  
Mating Type ◽  
Vegetative Growth ◽  
Point Mutations ◽  
Coiled Coil ◽  
Wild Type ◽  
Opposite Mating Type ◽  
Type Locus

Abstract The mating-type locus in the haploid filamentous fungus, Neurospora crassa, controls mating and sexual development. The fusion of reproductive structures of opposite mating type, A and a, is required to initiate sexual reproduction. However, the fusion of hyphae of opposite mating type during vegetative growth results in growth inhibition and cell death, a process that is mediated by the tol locus. Mutations in tol are recessive and suppress mating-type-associated heterokaryon incompatibility. In this study, we describe the cloning and characterization of tol. The tol gene encodes a putative 1011-amino-acid polypeptide with a coiled-coil domain and a leucine-rich repeat. Both regions are required for tol activity. Repeat-induced point mutations in tol result in mutants that are wild type during vegetative growth and sexual reproduction, but that allow opposite mating-type individuals to form a vigorous heterokaryon. Transcript analyses show that tol mRNA is present during vegetative growth but absent during a cross. These data suggest that tol transcription is repressed to allow the coexistence of opposite mating-type nuclei during the sexual reproductive phase. tol is expressed in a mat A, mat a, A/a partial diploid and in a mating-type deletion strain, indicating that MAT A-1 and MAT a-1 are not absolutely required for transcription or repression of tol. These data suggest that TOL may rather interact with MAT A-1 and/or MAT a-1 (or downstream products) to form a death-triggering complex.

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 MAR1—A REGULATOR OF THE HM  a AND HMα LOCI IN SACCHAROMYCES CEREVISIAE

Genetics ◽  
1979 ◽  
Vol 93 (1) ◽  
pp. 37-50
Author(s):  
Amar J S Klar ◽  
Seymour Fogel ◽  
Kathy Macleod
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Linkage Group ◽  
Mating Type ◽  
Group Iv ◽  
Genetic Evidence ◽  
Central Feature

ABSTRACT A mutation in the MAR1 (mating-type regulator) locus causing sterility in Saccharomyces cerevisiae is reported. The mutation maps on the left arm of linkage group IV between trp1 and cdc2 at a distance of about 27 CM from trp1 and about 31 cM from cdc2. Haploid strains with genotype MATα HMα HMa  mar1-1 and MATa HMα HMa mar1-1 are sterile. However, MATα hmα HMa mar1-1 and MATa HMα hma mar1-1 strains exhibit a and a mating type, respectively. The sterile strains can be "rare mated" with standard strains as a consequence of mutational changes at HMa and HMα. It is proposed that the MAR1 locus blocks the expression of MATα and MATa information thought to exist at HMa and HMα loci, respectively (HICKS, STRATHERN and HERSKOWITZ, 1977). In a mar1-1 mutant, the expression of both HMα and HMa information leads to a nonmating phenotype similar to that of MATa/MATα diploids. The genetic evidence reported here is consistent with a central feature of the "cassette model", namely that HMα and hma carry MATa information and HMa and hmα carry MATα information.

scholarly journals Functional analyses of the Neurospora crassa MT a-1 mating type polypeptide.

Genetics ◽  
1994 ◽  
Vol 137 (3) ◽  
pp. 715-722 ◽  
Author(s):  
M L Philley ◽  
C Staben
Keyword(s):  
Dna Binding ◽  
Neurospora Crassa ◽  
Mating Type ◽  
Dna Sequences ◽  
High Mobility ◽  
Binding Motif ◽  
Vegetative Incompatibility ◽  
Hmg Box

Abstract The Neurospora crassa mt a-1 gene, encoding the MT a-1 polypeptide, determines a mating type properties: sexual compatibility and vegetative incompatibility with A mating type. We characterized in vivo and in vitro functions of the MT a-1 polypeptide and specific mutant derivatives. MT a-1 polypeptide produced in Escherichia coli bound to specific DNA sequences whose core was 5'-CTTTG-3'. DNA binding was a function of the MT a-1 HMG box domain (a DNA binding motif found in high mobility group proteins and a diverse set of regulatory proteins). Mutation within the HMG box eliminated DNA binding in vitro and eliminated mating in vivo, but did not interfere with vegetative incompatibility function in vivo. Conversely, deletion of amino acids 216-220 of MT a-1 eliminated vegetative incompatibility, but did not affect mating or DNA binding. Deletion of the carboxyl terminal half of MT a-1 eliminated both mating and vegetative incompatibility in vivo, but not DNA binding in vitro. These results suggest that mating depends upon the ability of MT a-1 polypeptide to bind to, and presumably to regulate the activity of, specific DNA sequences. However, the separation of vegetative incompatibility from both mating and DNA binding indicates that vegetative incompatibility functions by a biochemically distinct mechanism.

Perithecial distribution patterns in standard and variant strains of Neurospora crassa

1981 ◽  
Vol 59 (12) ◽  
pp. 2610-2617 ◽  
Author(s):  
A. J. F. Griffiths ◽  
A. Rieck
Keyword(s):  
Neurospora Crassa ◽  
Genetic Control ◽  
Mating Type ◽  
Central Zone ◽  
Distribution Patterns ◽  
The Other ◽  
Clear Zone ◽  
Opposite Mating Type ◽  
Double Line ◽  
Inheritance Patterns

When crosses are made homozygous for the mutation fl, which completely eliminates conidiation, the patterns of sexual morphogenesis may be observed unobscured by effects due to conidia and conidial dispersal. In one cross, arbitrarily chosen as the standard, a striking double line of perithecia is seen, bordering a distinct clear central zone. Other crosses show a complex array of mating reactions, some involving an apparent invasion of one culture by nuclei of the opposite mating type, either through heterokaryotization or through overgrowth of one culture by the other. The width of the clear zone and the direction of invasion are variable and strain specific. The extent of heterokaryotization in the standard and variant crosses is discussed in relation to the situation found in other species. A complex genetic control of these reactions is indicated from inheritance patterns.

scholarly journals Some details and effects of the premeiotic controls of recombination frequencies in Neurospora crossa

1971 ◽  
Vol 18 (3) ◽  
pp. 255-264 ◽  
Author(s):  
B. C. Lamb
Keyword(s):  
Constant Temperature ◽  
Mating Type ◽  
Meiotic Recombination ◽  
Vegetative Growth ◽  
Adaptive Significance ◽  
Opposite Mating Type ◽  
Reciprocal Crosses ◽  
Temperature Regimes ◽  
Single Constant ◽  
Made In

SUMMARYRecombination data from crosses made at a single constant temperature of incubation were compared with those from crosses transferred to a different temperature at either the time of conidiation of protoperithecia by the strain of opposite mating-type, or after fertilization when crozier stages were first visible. Results were also compared from reciprocal crosses, from crosses made in different ways and from crosses in which protoperithecia were conidiated at different stages of maturity.Different temperature regimes during vegetative growth and proto-perithecial development had highly significant effects on subsequent meiotic recombination, while temperature differences during later premeiotic stages (between conidiation of protoperithecia and the crozier stage) had no or little effect. It was found that premeiotic controls could have as great, or greater, effects on meiotic recombination than those operating directly during meiosis. The possible adaptive significance of this is discussed.Recombination frequencies were affected by the method of making a cross (joint-inoculation of strains of opposite mating-type, or conidiation of protoperithecia), and by protoperithecial age at the time of conidiation by the opposite mating-type. Differences in recombination between reciprocal crosses were obtained and were dependent on temperature of incubation and age of protoperithecia at the time of conidiation. Recombination was not affected by different lysine concentrations in the medium. Genetic differences in premeiotic effector-production between the strains used were inferred.

GENETICALLY MIXED PERITHECIA AND SOMATIC RECOMBINATION IN A PSEUDO-WILD TYPE STRAIN OF NEUROSPORA CRASSA

1970 ◽  
Vol 12 (3) ◽  
pp. 547-552 ◽  
Author(s):  
A. Radford ◽  
S. F. H. Threlkeld
Keyword(s):  
Linkage Group ◽  
Neurospora Crassa ◽  
Recombination Event ◽  
Type Strain ◽  
Wild Type Strain ◽  
Group Iv ◽  
Wild Type ◽  
Somatic Recombination

In a pseudo-wild heterokaryon of Neurospora, mixed perithecia in a cross in which the heterokaryon is used as the protoperithecial parent may be common. In the present work, 4 out of 22 perithecia contained more than one female nuclear type.A somatic recombinant nucleus, resulting from nondisjunction at anaphase II followed by recombination prior to breakdown of the disomic nucleus has been identified. The recombination event occurred between pyr-1 and tryp-4 on linkage group IV.

Characterization of mat A-2, mat A-3 and ΔmatA Mating-Type Mutants of Neurospora crassa

Genetics ◽  
1998 ◽  
Vol 148 (3) ◽  
pp. 1069-1079 ◽  
Author(s):  
Adlane V-B Ferreira ◽  
Zhiqiang An ◽  
Robert L Metzenberg ◽  
N Louise Glass
Keyword(s):  
Neurospora Crassa ◽  
Mating Type ◽  
Sexual Development ◽  
Vegetative Growth ◽  
Double Mutant ◽  
Sexual Cycle ◽  
Wild Type ◽  
Type Locus ◽  
Isolation And Characterization

AbstractThe mating-type locus of Neurospora crassa regulates mating identity and entry into the sexual cycle. The mat A idiomorph encodes three genes, mat A-1, mat A-2, and mat A-3. Mutations in mat A-1 result in strains that have lost mating identity and vegetative incompatibility with mat a strains. A strain containing mutations in both mat A-2 and mat A-3 is able to mate, but forms few ascospores. In this study, we describe the isolation and characterization of a mutant deleted for mat (ΔmatA), as well as mutants in either mat A-2 or mat A-3. The ΔmatA strain is morphologically wild type during vegetative growth, but it is sterile and heterokaryon compatible with both mat A and mat a strains. The mat A-2 and mat A-3 mutants are also normal during vegetative growth, mate as a mat A strain, and produce abundant biparental asci in crosses with mat a, and are thus indistinguishable from a wild-type mat A strain. These data and the fact that the mat A-2 mat A-3 double mutant makes few asci with ascospores indicate that MAT A-2 and MAT A-3 are redundant and may function in the same pathway. Analysis of the expression of two genes (sdv-1 and sdv-4) in the various mat mutants suggests that the mat A polypeptides function in concert to regulate the expression of some sexual development genes.

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