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.

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.

scholarly journals Genetic recombination in Neurospora crassa and N. sitophila

1965 ◽  
Vol 6 (2) ◽  
pp. 216-225 ◽  
Author(s):  
M. B. Scott-Emuakpor
Keyword(s):  
Linkage Group ◽  
Neurospora Crassa ◽  
Mating Type ◽  
Genetic Recombination ◽  
Evolutionary Significance ◽  
Linkage Groups ◽  
Group Vi ◽  
Group I ◽  
Mutant Genes ◽  
Type Chromosome

Mutant genes in linkage groups I (mating-type chromosome), VI and VII have been transferred from Neurospora crassa to N. sitophila by hybridization and repeated backcrossing. Recombination between these genes has been studied from five-point crosses involving linkage group I and three-point crosses involving linkage groups VI and VII of the two species.The results show significant differences in the amount of recombination between some of the genes in the proximal regions of the mating-type chromosomes of the two species. They indicate proximal localization of crossovers in the mating-type chromosome of N. sitophila. The results also show significant differences in recombination frequency between the genes in linkage group VI and a close similarity in linkage group VII. They further show that the centromere in the two species may not be interfering with crossing-over in its vicinity to such an extent as to be of any evolutionary significance.

scholarly journals Interference studies in Neurospora crassa and N. sitophila

1965 ◽  
Vol 6 (2) ◽  
pp. 226-229 ◽  
Author(s):  
M. B. Scott-Emuakpor
Keyword(s):  
Linkage Group ◽  
Neurospora Crassa ◽  
Mating Type ◽  
Marker Genes ◽  
Linkage Groups ◽  
Group I ◽  
Interference Studies ◽  
Type Chromosome ◽  
Chiasma Interference

Tetrad data from five-point crosses involving linkage group I (mating-type chromosome) and three-point crosses involving linkage groups VI and VII of Neurospora crassa and N. sitophila have been analysed in order to detect the phenomena of chromatid and chiasma interference on a comparative basis. Marker genes were transferred from N. crassa to N. sitophila by hybridization and repeated back crossing. The details of the methods of transfer and of making crosses have been described in a previous paper (Scott-Emuakpor, 1965).

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.

Cloning, sequence, and photoregulation of al-1, a carotenoid biosynthetic gene of Neurospora crassa

1990 ◽  
Vol 10 (10) ◽  
pp. 5064-5070
Author(s):  
T J Schmidhauser ◽  
F R Lauter ◽  
V E Russo ◽  
C Yanofsky
Keyword(s):  
Linkage Group ◽  
Neurospora Crassa ◽  
Carotenoid Biosynthesis ◽  
Mrna Levels ◽  
Biosynthetic Gene ◽  
Biosynthetic Enzyme ◽  
Group I ◽  
Phytoene Dehydrogenase ◽  
Initiation Of Transcription ◽  
Residue Polypeptide

Carotenoid biosynthesis is regulated by blue light during growth of Neurospora crassa mycelia. We have cloned the al-1 gene of N. crassa encoding the carotenoid-biosynthetic enzyme phytoene dehydrogenase and present an analysis of its structure and regulation. The gene encodes a 595-residue polypeptide that shows homology to two procaryotic carotenoid dehydrogenases. RNA measurements showed that the level of al-1 mRNA increased over 70-fold in photoinduced mycelia. Transcription run-on studies indicated that the al-1 gene was regulated at the level of initiation of transcription in response to photoinduction. The photoinduced increase of al-1 mRNA levels was not observed in two Neurospora mutants defective in all physiological photoresponses. Analysis of cosmid containing al-1 and of a translocation strain with a breakpoint within al-1 indicated that al-1 transcription proceeds towards the centromere of linkage group I of N. crassa.

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.

GENETIC AND COMPLEMENTATION STUDIES OF A NEW CAROTENOID MUTANT OF NEUROSPORA CRASSA

1968 ◽  
Vol 10 (2) ◽  
pp. 351-356 ◽  
Author(s):  
R. E. Subden ◽  
S. F. H. Threlkeld
Keyword(s):  
Linkage Group ◽  
Neurospora Crassa ◽  
Biosynthetic Pathway ◽  
Group I ◽  
The Right

A spontaneously occurring mutant called "yellow b" has been isolated and mapped on the right arm of linkage group I in Neurospora crassa 0.15 c.o.u. distal to aur and 2 c.o.u. distal to al-2. These three markers complement each other and are involved in the same biosynthetic pathway.

scholarly journals Interspecific crosses and crossing-over in Neurospora

1972 ◽  
Vol 19 (2) ◽  
pp. 115-119 ◽  
Author(s):  
K. D. Newcombe ◽  
S. F. H. Threlkeld
Keyword(s):  
Linkage Group ◽  
Neurospora Crassa ◽  
Interspecific Crosses ◽  
Crossing Over ◽  
Centromere Region ◽  
Group I

SUMMARYThrough a series of backcrosses the centromere region of linkage group I of Neurospora crassa was transferred to the N. sitophila genome, and through another series of backcrosses the centromere region of linkage group I of N. sitophila was transferred to N. crassa. Strains thus synthesized showed, in further crosses, that the N. sitophila centromere region acts as a dominant enhancer of cross-over frequencies across linkage group I of the two species.

AN INTERSTITIAL PERICENTRIC INVERSION IN NEUROSPORA

1982 ◽  
Vol 24 (6) ◽  
pp. 693-703 ◽  
Author(s):  
Edward G. Barry ◽  
John F. Leslie
Keyword(s):  
Linkage Group ◽  
Neurospora Crassa ◽  
Gene Order ◽  
Pericentric Inversion ◽  
Inverted Segment ◽  
Chromosome Inversions ◽  
Central Segment ◽  
Group I ◽  
Higher Eukaryotes ◽  
Inversion Loop

In ln(IL; IR)OY323 of Neurospora crassa, a long central segment of linkage group I is inverted that includes the centromere. This is the first interstitial pericentric inversion to be identified in a fungus. In genetic and cytological behavior, it resembles chromosome inversions in higher eukaryotes. In crosses heterozygous for the OY323 inversion, normally distant markers are closely linked, while in homozygous inversion crosses the gene order is reversed, but recombination is approximately normal within the inverted segment. A characteristic inversion loop may form at pachytene in heterozygous crosses; frequently, segments distal to the breakpoints do not pair, however. Rearrangement breakpoints were mapped precisely by duplication coverage using appropriate recessive markers in crosses of OY323 with a partially overlapping inversion, In(IL→IR)NM176.

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