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.

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.

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.

Genetic control of plasma membrane adhesion and fusion in Chlamydomonas gametes

1987 ◽  
Vol 88 (5) ◽  
pp. 613-621
Author(s):  
C.L. Forest
Keyword(s):  
Plasma Membrane ◽  
Chlamydomonas Reinhardtii ◽  
Genetic Control ◽  
Mating Type ◽  
Opposite Mating Type ◽  
Gamete Fusion ◽  
Gamete Interaction ◽  
Structure Interaction ◽  
Mating Structure ◽  
Membrane Adhesion

The final stages of gamete interaction in Chlamydomonas reinhardtii occur between the specialized plasma membrane organelles (mating structures) of opposite mating-type cells. A number of mutants affecting these interactions have been obtained in several laboratories; all have been defined as fusion-defective. This paper demonstrates that there are at least two genetically definable stages of mating-structure interaction: (1) the recognition/adhesion of mating structures, and (2) gamete fusion. The possibility that these two functions, the adhesion and subsequent fusion of mating structures, may be mating-type specific is raised, since of the seven independently isolated mutants analysed, all mutants defective in fusion are of mating-type (-), and only mating type (+) mutants show defects in adhesion.

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 GENES INFLUENCING SELECTIVE FERTILIZATION IN NEUROSPORA CRASSA

Genetics ◽  
1972 ◽  
Vol 70 (4) ◽  
pp. 511-519
Author(s):  
Takeshi Egashira ◽  
Kuzuo Nakamura
Keyword(s):  
Neurospora Crassa ◽  
Mating Type ◽  
Genetic Similarity ◽  
Mutant Gene ◽  
Opposite Mating Type ◽  
Cytoplasmic Effect ◽  
Mutual Attraction ◽  
Color Mutant ◽  
Different Strains

ABSTRACT The mutual attraction of conidia to protoperithecia of the opposite mating type was studied genetically in crosses where a mixture of conidia from two different strains, one of which was marked by an ascospore color mutant gene tan spore (ts), was applied to protoperithecia. Selective fertilization was measured as the frequency of perithecia fertilized by conidia from one strain in competition with conidia from another strain. Selective fertilization by a given strain varied throughout the range from 10 to 97% according to the strains of protoperithecial parent. The selective fertilization was revealed to be under the control of two or more loci, which appeared to have multiplicative action. No indication of a cytoplasmic effect on selective fertilization was obtained. The strength of the mutual attraction between conidia and protoperithecia decreased as genetic similarity increased.

scholarly journals Expression of meiotic drive elements Spore killer-2 and Spore killer-3 in asci of Neurospora tetrasperma.

Genetics ◽  
1991 ◽  
Vol 129 (1) ◽  
pp. 25-37 ◽  
Author(s):  
N B Raju ◽  
D D Perkins
Keyword(s):  
Linkage Group ◽  
Neurospora Crassa ◽  
Mating Type ◽  
Meiotic Drive ◽  
The Other ◽  
Wild Type ◽  
Group Iii ◽  
Neurospora Tetrasperma ◽  
Spore Killer ◽  
Variable Penetrance

Abstract It was shown previously that when a chromosomal Spore killer factor is heterozygous in Neurospora species with eight-spored asci, the four sensitive ascospores in each ascus die and the four survivors are all killers. Sk-2K and Sk-3K are nonrecombining haplotypes that segregate with the centromere of linkage group III. No killing occurs when either one of these killers is homozygous, but each is sensitive to killing by the other in crosses of Sk-2K x Sk-3K. In the present study, Sk-2K and Sk-3K were transferred by recurrent backcrosses from the eight-spored species Neurospora crassa into Neurospora tetrasperma, a pseudohomothallic species which normally makes asci with four large spores, each heterokaryotic for mating type and for any other centromere-linked genes that are heterozygous in the cross. The action of Sk-2K and Sk-3K in N. tetrasperma is that predicted from their behavior in eight-spored species. A sensitive nucleus is protected from killing if it is enclosed in the same ascospore with a killer nucleus. Crosses of Sk-2K x Sk-2S, Sk-3K x Sk-3S, and Sk-sK x Sk-3K all produce four-spored asci that are wild type in appearance, with the ascospores heterokaryotic and viable. The Eight-spore gene E, which shows variable penetrance, was used to obtain N. tetrasperma asci in which two to eight spores are small and homokaryotic. When killer and sensitive alleles are segregating in the presence of E, only those ascospores that contain a killer allele survive. Half of the small ascospores are killed. In crosses of Sk-2K x Sk-3K (with E heterozygous), effectively all small ascospores are killed. The ability of N. tetrasperma to carry killer elements in cryptic condition suggests a possible role for Spore killers in the origin of pseudohomothallism, with adoption of the four-spored mode restoring ascospore viability of crosses in which killing would otherwise occur.

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.

scholarly journals GENETIC CONTROL OF HETEROCARYOSIS IN NEUROSPORA CRASSA

Genetics ◽  
1955 ◽  
Vol 40 (1) ◽  
pp. 117-129
Author(s):  
Bruce W Holloway
Keyword(s):  
Neurospora Crassa ◽  
Genetic Control
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