scholarly journals High-frequency conversion to a "fluffy" developmental phenotype in Aspergillus spp. by 5-azacytidine treatment: evidence for involvement of a single nuclear gene.

1983 ◽  
Vol 3 (12) ◽  
pp. 2287-2297 ◽  
Author(s):  
M Tamame ◽  
F Antequera ◽  
J R Villanueva ◽  
T Santos
Keyword(s):  
Dna Methylation ◽  
High Frequency ◽  
Frequency Conversion ◽  
Nuclear Gene ◽  
Wild Type ◽  
Mendelian Segregation ◽  
Target Action ◽  
Aerial Hyphae ◽  
High Fraction ◽  
Chromosome Viii

Transient exposure of mycelia from Aspergillus niger and Aspergillus nidulans to the cytidine analog 5-azacytidine, leading to no more than 0.3 to 0.5% substitution for cytosine by 5-azacytosine in A. nidulans DNA, resulted in the conversion of a high fraction of the cell population (more than 20%) to a mitotically and meiotically stable "fluffy" developmental phenotype. The phenotypic variants are characterized by the developmentally timed production of a profuse fluffy network of undifferentiated aerial hyphae that seem to escape signals governing vegetative growth. Genetic analysis with six different fluffy clones reveals that this trait is not cytoplasmically coded, is recessive in heterozygous diploids but codominant in heterokaryons, and exhibits a 1:1 Mendelian segregation pattern upon sexual sporulation of heterozygous diploids. Complementation and mitotic haploidization studies indicated that all variants are affected in the same gene, which can be tentatively located on chromosome VIII of A. nidulans. Molecular analysis to search for modified bases showed that DNA methylation is negligible in in both A. niger and A. nidulans and that no differences could be detected among DNAs from wild-type cells, fluffy clones, or mycelia exposed to 5-azacytidine. It thus appears that high-frequency conversion of fungal mycelia to a stable, variant developmental phenotype by 5-azacytidine is the result of some kind of target action on a single nuclear gene and that this conversion can occur in organisms virtually devoid of DNA methylation.

High-frequency conversion to a "fluffy" developmental phenotype in Aspergillus spp. by 5-azacytidine treatment: evidence for involvement of a single nuclear gene

1983 ◽  
Vol 3 (12) ◽  
pp. 2287-2297
Author(s):  
M Tamame ◽  
F Antequera ◽  
J R Villanueva ◽  
T Santos
Keyword(s):  
Dna Methylation ◽  
High Frequency ◽  
Frequency Conversion ◽  
Nuclear Gene ◽  
Wild Type ◽  
Mendelian Segregation ◽  
Target Action ◽  
Aerial Hyphae ◽  
High Fraction ◽  
Chromosome Viii

Transient exposure of mycelia from Aspergillus niger and Aspergillus nidulans to the cytidine analog 5-azacytidine, leading to no more than 0.3 to 0.5% substitution for cytosine by 5-azacytosine in A. nidulans DNA, resulted in the conversion of a high fraction of the cell population (more than 20%) to a mitotically and meiotically stable "fluffy" developmental phenotype. The phenotypic variants are characterized by the developmentally timed production of a profuse fluffy network of undifferentiated aerial hyphae that seem to escape signals governing vegetative growth. Genetic analysis with six different fluffy clones reveals that this trait is not cytoplasmically coded, is recessive in heterozygous diploids but codominant in heterokaryons, and exhibits a 1:1 Mendelian segregation pattern upon sexual sporulation of heterozygous diploids. Complementation and mitotic haploidization studies indicated that all variants are affected in the same gene, which can be tentatively located on chromosome VIII of A. nidulans. Molecular analysis to search for modified bases showed that DNA methylation is negligible in in both A. niger and A. nidulans and that no differences could be detected among DNAs from wild-type cells, fluffy clones, or mycelia exposed to 5-azacytidine. It thus appears that high-frequency conversion of fungal mycelia to a stable, variant developmental phenotype by 5-azacytidine is the result of some kind of target action on a single nuclear gene and that this conversion can occur in organisms virtually devoid of DNA methylation.

EVIDENCE OF EXTRACHROMOSOMAL INHERITANCE IN CHENOPODIUM RUBRUM

1968 ◽  
Vol 10 (4) ◽  
pp. 876-885 ◽  
Author(s):  
Beatrice E. Murray ◽  
Iris L. Craig
Keyword(s):  
Virus Infection ◽  
High Frequency ◽  
Mutation Frequency ◽  
Gene Action ◽  
Chenopodium Rubrum ◽  
X Rays ◽  
Chromosomal Gene ◽  
Wild Type ◽  
Mendelian Segregation ◽  
Extrachromosomal Inheritance

A curled-leaf mutation (Cu) was induced in Chenopodium rubrum by diethyl sulphate treatment and reversed in high frequency (21.5%) by X-rays. Nonchromosomal inheritance is demonstrated for the Cu mutation. Evidence for nonchromosomal inheritance is based on mutation frequency; mutagenic specificity, non-Mendelian segregation; and an absence of segregation in wild type backcrosses. Biparental transmission and independent assortment in back-cross progenies was also shown. Evidence in support of chromosomal gene action and the lack of virus infection as a basis of the mutation is also discussed.

scholarly journals A buff spore colour mutant in Sordaria brevicollis showing high-frequency conversion: 2. Loss of the high-frequency conversion

1983 ◽  
Vol 41 (2) ◽  
pp. 155-163 ◽  
Author(s):  
Mary V. Macdonald ◽  
Harold L. K. Whitehouse
Keyword(s):  
Nucleotide Sequence ◽  
High Frequency ◽  
Frequency Conversion ◽  
Recessive Gene ◽  
Initiation Site ◽  
Dominant Allele ◽  
Single Recessive Gene ◽  
Wild Type ◽  
Colour Mutant ◽  
Conversion Frequency

SUMMARYA mutant, YS17, at the buff spore colour locus in Sordaria brevicollis has previously been described. It shows conversion with high frequency, predominantly to wild type, and is believed to act as a recognition site for an endonuclease that initiates recombination at the YS17 site. The discovery is now reported of a gene that causes loss of the high-frequency conversion shown by the YS17 mutant. The gene was present in existing stocks of the fungus. It reduces the conversion frequency of YS17 to a level similar to that of other buff mutants, from which it is inferred that the YS17 mutant no longer acts as an initiation site for recombination. When the conversion frequency of YS17 is low the bias in conversion to wild type rather than to mutant is lost, suggesting that this bias may relate to the initiation of recombination at the site. The loss of high frequency conversion of YS17 appears to be determined by a single recessive gene linked to mating type and unlinked to buff. It is suggested that the dominant allele induces recombination at the site of YS17 by controlling either the synthesis or the activity of an endonuclease that is capable of recognising the nucleotide sequence at the YS17 site. Some anomalous results point to the existence of modifiers of the action of the gene.

scholarly journals Suppressors of ‘blue’ mutations in yeast

1974 ◽  
Vol 23 (1) ◽  
pp. 37-45 ◽  
Author(s):  
I. de G. Mitchell ◽  
E. A. Bevan
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Methylene Blue ◽  
Temperature Sensitivity ◽  
High Frequency ◽  
Agar Medium ◽  
Nuclear Gene ◽  
Nutrient Agar ◽  
Wild Type ◽  
Cytoplasmic Factor ◽  
Nutrient Agar Medium

SummaryMutants ofSaccharomyces cerevisiaewhose colonies were blue when grown on nutrient agar medium containing methylene blue reverted to wild-type with white-colony phenotype at high frequency. This reversion was controlled by nuclear gene suppressors in some mutants, and by cytoplasmic suppressors in others. Each of the latter suppressed several independetly segregating blue mutants. These suppressors could be divided into two classes: suppression by petite mutations which behaved as recessives, and suppression by a cytoplasmic factor in respiration-sufficient cells which behaved as dominant over wild-type but might also be a mutation ofrho. A relationship between blue mutation and temperature sensitivity was suggested.

scholarly journals A buff spore colour mutant in Sordaria brevicollis showing high-frequency conversion

1979 ◽  
Vol 34 (2) ◽  
pp. 87-119 ◽  
Author(s):  
Mary V. Macdonald ◽  
Harold L. K. Whitehouse
Keyword(s):  
High Frequency ◽  
Recombination Event ◽  
Frequency Conversion ◽  
Crossing Over ◽  
Wild Type ◽  
Heteroduplex Dna ◽  
Colour Mutant ◽  
The Right ◽  
Postmeiotic Segregation ◽  
Single Enzyme

SUMMARYA mutant, YS17, at the buff spore colour locus in Sordaria brevicollis, when crossed with wild type, gives rise to aberrant asci with a frequency over 10 times that of other buff mutants. Over 98% of the aberrant asci have 6 wild type and 2 mutant spores. From tests with another buff mutant it is concluded that loss of the mutant spore colour when YS17 shows conversion to wild type is associated with loss of the high frequency conversion, and that both characters are caused by the same mutation. A methionine-requiring mutant (met-1) has been obtained that maps 5 units to the left of buff, and this, together with the nicotinamide-requiring mutant (nic-1) 2 units to the right, has provided flanking markers for buff that can be scored with complete reliability. Crosses between YS17 and 28 other buff mutants have revealed close linkage to three of them which map to its right on the basis of flanking marker behaviour, all the others mapping to its left. The frequency of postmeiotic segregation at the sites of buff mutants near to the site of YS17 is greatly increased in the presence of YS17, and occurs in the chromatid showing conversion to wild type at YS17.From these and other results, obtained largely by ascus analysis, the following conclusions have been drawn.(1) The YS17 mutation is probably acting as a recognition site for an endonuclease that initiates recombination, with the result that the frequency of heteroduplex DNA within the buff gene is much increased.(2) The recombination initiated at YS17 is asymmetric (or at least pre-dominantly so), with the YS17 site acting as a recipient of a nucleotide chain from the other parent, not a donor to it.(3) The frequency of crossing over associated with conversion at YS17 is variable: about 30% in crosses with most of the buff mutants, about half this value in crosses with wild type, and almost zero in crosses with closely-linked buff mutants.(4) In about one third of the crossover asci in crosses between YS17 and other buff mutants the crossover is not adjacent to the site of YS17 but separated from it by the site of the allele, which shows normal 4:4 segregation.(5) It seems necessary to revive the idea of more than one recombination event in proximity, a non-crossover conversion event sometimes leading to a second event – a crossover – in the vicinity. It is tentatively suggested that both might be controlled by a single enzyme aggregate.

scholarly journals DNA methylation patterns identify subgroups of pancreatic neuroendocrine tumors with clinical association

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Vanessa Lakis ◽  
◽  
Rita T. Lawlor ◽  
Felicity Newell ◽  
Ann-Marie Patch ◽  
...  
Keyword(s):  
Dna Methylation ◽  
Neuroendocrine Tumors ◽  
Methylation Profile ◽  
Pancreatic Neuroendocrine Tumors ◽  
Wild Type ◽  
Genomic Information ◽  
Chromosome 11 ◽  
Dna Methylation Profile ◽  
Methylation Patterns ◽  
Recurrent Patterns

AbstractHere we report the DNA methylation profile of 84 sporadic pancreatic neuroendocrine tumors (PanNETs) with associated clinical and genomic information. We identified three subgroups of PanNETs, termed T1, T2 and T3, with distinct patterns of methylation. The T1 subgroup was enriched for functional tumors and ATRX, DAXX and MEN1 wild-type genotypes. The T2 subgroup contained tumors with mutations in ATRX, DAXX and MEN1 and recurrent patterns of chromosomal losses in half of the genome with no association between regions with recurrent loss and methylation levels. T2 tumors were larger and had lower methylation in the MGMT gene body, which showed positive correlation with gene expression. The T3 subgroup harboured mutations in MEN1 with recurrent loss of chromosome 11, was enriched for grade G1 tumors and showed histological parameters associated with better prognosis. Our results suggest a role for methylation in both driving tumorigenesis and potentially stratifying prognosis in PanNETs.

Normal Synaptonemal Complex and Abnormal Recombination Nodules in Two Alleles of the Drosophila Meiotic Mutant mei-W68

Genetics ◽  
2003 ◽  
Vol 163 (4) ◽  
pp. 1337-1356 ◽  
Author(s):  
Adelaide T C Carpenter
Keyword(s):  
Electron Microscopy ◽  
Synaptonemal Complex ◽  
High Frequency ◽  
Serial Section ◽  
The Other ◽  
Wild Type ◽  
Recombination Nodules ◽  
Section Electron ◽  
Serial Section Electron Microscopy ◽  
Section Electron Microscopy

Abstract The meiotic phenotypes of two mutant alleles of the mei-W68 gene, 1 and L1, were studied by genetics and by serial-section electron microscopy. Despite no or reduced exchange, both mutant alleles have normal synaptonemal complex. However, neither has any early recombination nodules; instead, both exhibit high numbers of very long (up to 2 μm) structures here named “noodles.” These are hypothesized to be formed by the unchecked extension of identical but much shorter structures ephemerally seen in wild type, which may be precursors of early recombination nodules. Although the mei-W68L1 allele is identical to the mei-W681 allele in both the absence of early recombination nodules and a high frequency of noodles (i.e., it is amorphic for the noodle phene), it is hypomorphic in its effects on exchange and late recombination nodules. The differential effects of this allele on early and late recombination nodules are consistent with the hypothesis that Drosophila females have two separate recombination pathways—one for simple gene conversion, the other for exchange.

scholarly journals Mutational Activation of a Gαi Causes Uncontrolled Proliferation of Aerial Hyphae and Increased Sensitivity to Heat and Oxidative Stress in Neurospora crassa

Genetics ◽  
1999 ◽  
Vol 151 (1) ◽  
pp. 107-117
Author(s):  
Qi Yang ◽  
Katherine A Borkovich
Keyword(s):  
Signal Transduction ◽  
Neurospora Crassa ◽  
Signal Transduction Pathway ◽  
Sexual Cycle ◽  
Intracellular Camp ◽  
Wild Type ◽  
Independent Functions ◽  
Aerial Hyphae ◽  
Mutational Activation ◽  
Camp Levels

Abstract Heterotrimeric G proteins, consisting of α, β, and γ subunits, transduce environmental signals through coupling to plasma membrane-localized receptors. We previously reported that the filamentous fungus Neurospora crassa possesses a Gα protein, GNA-1, that is a member of the Gαi superfamily. Deletion of gna-1 leads to defects in apical extension, differentiation of asexual spores, sensitivity to hyperosmotic media, and female fertility. In addition, Δgna-1 strains have lower intracellular cAMP levels under conditions that promote morphological abnormalities. To further define the function of GNA-1 in signal transduction in N. crassa, we examined properties of strains with mutationally activated gna-1 alleles (R178C or Q204L) as the only source of GNA-1 protein. These mutations are predicted to inhibit the GTPase activity of GNA-1 and lead to constitutive signaling. In the sexual cycle, gna-1R178C and gna-1Q204L strains are female-fertile, but produce fewer and larger perithecia than wild type. During asexual development, gna-1R178C and gna-1Q204L strains elaborate abundant, long aerial hyphae, produce less conidia, and possess lower levels of carotenoid pigments in comparison to wild-type controls. Furthermore, gna-1R178C and gna-1Q204L strains are more sensitive to heat shock and exposure to hydrogen peroxide than wild-type strains, while Δgna-1 mutants are more resistant. In contrast to Δgna-1 mutants, gna-1R178C and gna-1Q204L strains have higher steady-state levels of cAMP than wild type. The results suggest that GNA-1 possesses several Gβγ-independent functions in N. crassa. We propose that GNA-1 mediates signal transduction pathway(s) that regulate aerial hyphae development and sensitivity to heat and oxidative stresses, possibly through modulation of cAMP levels.

scholarly journals Mutants inSaccharomyces lactiscontrolling both β-glucosidase and β-galactosidase activities

1972 ◽  
Vol 19 (1) ◽  
pp. 27-32 ◽  
Author(s):  
M. Tingle ◽  
H. O. Halvorson
Keyword(s):  
Nuclear Gene ◽  
Mutant Phenotype ◽  
Single Mutation ◽  
Wild Type ◽  
Genetic Studies ◽  
Glucosidase Activity ◽  
Type Strains

SUMMARYInSaccharomyces lactis, a class of mutants isolated for low β-glucosidase activity are reduced in activity for β-galactosidase as well. Genetic studies indicate that their properties are the result of a single mutation in a nuclear gene. In diploide containing a wild-type and mutant β-galactosidase allele, the mutant phenotype is partially dominant. The two enzymes can be separated physically and under appropriate conditions are induced independently in wild-type strains.

scholarly journals The ham-2 Locus, Encoding a Putative Transmembrane Protein, Is Required for Hyphal Fusion in Neurospora crassa

Genetics ◽  
2002 ◽  
Vol 160 (1) ◽  
pp. 169-180
Author(s):  
Qijun Xiang ◽  
Carolyn Rasmussen ◽  
N Louise Glass
Keyword(s):  
Neurospora Crassa ◽  
Somatic Cell ◽  
Molecular Mechanism ◽  
Cell Fusion ◽  
Deletion Mutant ◽  
Transmembrane Protein ◽  
Wild Type ◽  
Vegetative Incompatibility ◽  
Hyphal Fusion ◽  
Aerial Hyphae

Abstract Somatic cell fusion is common during organogenesis in multicellular eukaryotes, although the molecular mechanism of cell fusion is poorly understood. In filamentous fungi, somatic cell fusion occurs during vegetative growth. Filamentous fungi grow as multinucleate hyphal tubes that undergo frequent hyphal fusion (anastomosis) during colony expansion, resulting in the formation of a hyphal network. The molecular mechanism of the hyphal fusion process and the role of networked hyphae in the growth and development of these organisms are unexplored questions. We use the filamentous fungus Neurospora crassa as a model to study the molecular mechanism of hyphal fusion. In this study, we identified a deletion mutant that was restricted in its ability to undergo both self-hyphal fusion and fusion with a different individual to form a heterokaryon. This deletion mutant displayed pleiotropic defects, including shortened aerial hyphae, altered conidiation pattern, female sterility, slow growth rate, lack of hyphal fusion, and suppression of vegetative incompatibility. Complementation with a single open reading frame (ORF) within the deletion region in this mutant restored near wild-type growth rates, female fertility, aerial hyphae formation, and hyphal fusion, but not vegetative incompatibility and wild-type conidiation pattern. This ORF, which we named ham-2 (for hyphal anastomosis), encodes a putative transmembrane protein that is highly conserved, but of unknown function among eukaryotes.

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