scholarly journals ISOLATION AND CHARACTERIZATION OF NEUROSPORA MUTANTS AFFECTED IN INVERTASE SYNTHESIS

Genetics ◽  
1984 ◽  
Vol 106 (4) ◽  
pp. 591-599
Author(s):  
Deborah B Lee ◽  
Stephen J Free
Keyword(s):  
Neurospora Crassa ◽  
Large Scale ◽  
Invertase Activity ◽  
Free Medium ◽  
Wild Type ◽  
Isolation And Characterization ◽  
Normal Enzyme ◽  
Enzyme Molecules ◽  
Large Scale Screening

ABSTRACT We have outlined a procedure that allows the large-scale screening of mutagenized Neurospora crassa populations for invertaseless mutants. We have isolated and characterized three mutations, inv(DBL1), inv(DBL9) and inv(DBL14), which have been mapped at or near the invertase structural gene. One of these, inv(DBL1), is particularly interesting. Our experiments indicate that the reduced level of invertase activity in the inv(DBL1)-containing cell can be explained as the result of a reduced number of normal enzyme molecules. We also show that wild-type Neurospora is able to respond rapidly to a change of medium and can dramatically increase its production of invertase within 20 min after a transfer to a carbon-free medium.

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.

scholarly journals ISOLATION AND CHARACTERIZATION OF LIGHT-INSENSITIVE MUTANTS OF NEUROSPORA CRASSA

Genetics ◽  
1983 ◽  
Vol 104 (1) ◽  
pp. 11-21
Author(s):  
John Paietta ◽  
Malcolm L Sargent
Keyword(s):  
Genetic Analysis ◽  
Neurospora Crassa ◽  
Blue Light ◽  
Light Sensitivity ◽  
Phase Shifting ◽  
Nuclear Genes ◽  
Wild Type ◽  
Linkage Groups ◽  
Isolation And Characterization

ABSTRACT As part of a genetic analysis of blue light photoreception in Neurospora, three mutants were isolated that do not exhibit photosuppression of circadian conidiation, i.e., they show periodic conidiation in constant light. The mutations have been given the designations lis-1, lis-2 and lis-3 ("light insensitive"). The three mutations segregate as single nuclear genes, are nonallelic and are recessive to wild type in heterokaryon tests. The linkage groups of the mutations are as follows: lis-1, I; lis-2, VI; and lis-3, V. The light -insensitive phenotype of the mutants is restricted to the photosuppression response; other responses such as photoinduced phase shifting of the conidiation rhythm and photoinduced carotenogenesis are not altered. The physiological or biochemical defects of the mutants have not been established, but they are not similar to previous reported cases (i.e., rib and poky) in which a reduction in light sensitivity has been observed.

Isolation and characterization of Azotobacter vinelandii mutant strains with potential as bacterial fertilizer

1983 ◽  
Vol 29 (8) ◽  
pp. 973-978 ◽  
Author(s):  
Joyce K. Gordon ◽  
Marty R. Jacobson
Keyword(s):  
Azotobacter Vinelandii ◽  
Nitrogenase Activity ◽  
Resistant Mutant ◽  
Free Medium ◽  
Wild Type ◽  
Isolation And Characterization ◽  
Mutant Strains ◽  
Resistant Strains ◽  
Resistant Mutants

Mutant strains of Azotobacter vinelandii which might have potential for use as bacterial fertilizer have been isolated and fall into two categories: constitutive mutants that synthesize nitrogenase in the presence of ammonium and mutants that overproduce nitrogenase when grown in nitrogen-free medium. The constitutive mutants described in this paper were isolated from the wild type as methylalanine-resistant strains and express up to 23% of the fully derepressed nitrogenase level when grown in medium containing excess ammonium. By contrast, ammonium-grown cultures of wild type have less than 0.003% of the fully derepressed level. Strains which fix more N2 than the wild type in nitrogen-free medium were isolated as mefhylammonium-resistant mutants. Although the methylammonium-resistant mutant strains fix more N2 than the wild type, they grow no faster. The excess nitrogen produced by these mutants is excreted into the medium, resulting in up to 60% more nitrogen than in the medium of the wild type. Higher nitrogenase activity in the methylammonium-resistant mutant strains was found to be a result of increased levels of nitrogenase protein, suggesting that regulation of nitrogenase synthesis may be altered.

scholarly journals ISOLATION AND CHARACTERIZATION OF NUCLEASE MUTANTS IN NEUROSPORA CRASSA

Genetics ◽  
1969 ◽  
Vol 63 (1) ◽  
pp. 75-92
Author(s):  
T Ishikawa ◽  
A Toh-E ◽  
I Uno ◽  
K Hasunuma
Keyword(s):  
Neurospora Crassa ◽  
Isolation And Characterization

scholarly journals Isolation and characterization of the SPT2 gene, a negative regulator of Ty-controlled yeast gene expression.

1985 ◽  
Vol 5 (7) ◽  
pp. 1543-1553 ◽  
Author(s):  
G S Roeder ◽  
C Beard ◽  
M Smith ◽  
S Keranen
Keyword(s):  
Gene Product ◽  
Regulatory Region ◽  
Negative Regulator ◽  
Transcriptional Level ◽  
Wild Type ◽  
Isolation And Characterization ◽  
Mutant Strains ◽  
Insertion Mutations ◽  
His4 Gene

The his4-917 mutation of Saccharomyces cerevisiae results from the insertion of the Ty element Ty917 into the regulatory region of the HIS4 gene and renders the cell His-. The hist4-912 delta mutant, which carries a solo delta in the 5'-noncoding region of HIS4, is His+ at 37 degrees C but His- at 23 degrees C. Both these mutations interfere with HIS4 expression at the transcriptional level. The His- phenotype of both insertion mutations is suppressed by mutations at the SPT2 locus. The product of the wild-type SPT2 gene apparently represses HIS4 transcription in these mutant strains; this repression is relieved when the SPT2 gene is destroyed by mutation. The repression of transcription by SPT2 presumably results from an interaction between the SPT2+ gene product and Ty or delta sequences. In this paper, we report the cloning and DNA sequence analysis of the wild-type SPT2 gene and show that the gene is capable of encoding a protein of 333 amino acids in length. In addition, we show that a dominant mutation of the SPT2 gene results from the generation of an ochre codon which is presumed to lead to a shortened SPT2 gene product.

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