scholarly journals Resistance to amino acid analogues in Coprinus: Dominance modifier genes and dominance reversal in dikaryons and diploids

1975 ◽  
Vol 25 (2) ◽  
pp. 95-107 ◽  
Author(s):  
S. Senathirajah ◽  
D. Lewis
Keyword(s):  
Carboxylic Acid ◽  
Single Gene ◽  
Modifier Genes ◽  
Wild Type ◽  
Recessive Resistance ◽  
Amino Acid Analogues ◽  
Resistant Mutants ◽  
Selection For ◽  
Oligomeric Product ◽  
Type Strains

SUMMARYWild-type strains of Coprinus lagopus are sensitive to para-fluoro-phenylalanine and ethionine. Resistant mutants to these two analogues are known but all these mutants are recessive in a heterozygous dikaryon except for F7 (pfpr-3) which is semi-dominant. Resistance to two other analogues, however – canavanine sulphate and azetidine-2-carboxylic acid – were found to be wild-type features. One strain of C. lagopus sensitive to canavanine was identified. Selection for canavanine resistance in monokaryons always yielded only dominant resistance, while selection for para-fluorophenylalanine resistance in monokaryons gave only recessive resistance. Canavanine-resistant mutants were due to a single gene mutation which, like the wild-type resistance, were dominant in heterozygous dikaryons. The wild-type resistance was also dominant in a diploid but the mutant resistance was recessive. Selection for resistance to para-fluorophenylalanine in auxotrophically balanced dikaryons resulted in the identification of two new loci (pfpr-10 and pfpr-ll), and two specific dominance modifiers (mod+-10 and mod+-ll). In the absence of the specific modifier, pfpr-10 and pfpr-ll were recessive while, in the presence of even one dose of the specific modifier, resistance was dominant in the dikaryon. The pfpr-10 and pfpr-ll even in the presence of two doses of modifier were fully recessive in the diploid. The action of the modifier genes and the reversal of dominance in dikaryon and diploid is discussed in terms of negative complementation in an oligomeric product of the pfpr gene and localized translation of the relevant mRNA in the cell with the modifier acting as a reinforcer of localization.

scholarly journals A genetic analysis of resistance to nystatin inSaccharomyces cerevisiae

1967 ◽  
Vol 9 (2) ◽  
pp. 179-193 ◽  
Author(s):  
K. A. Ahmed ◽  
R. A. Woods
Keyword(s):  
Genetic Analysis ◽  
Resistance Genes ◽  
Type Strain ◽  
Wild Type Strain ◽  
Second Step ◽  
Wild Type ◽  
Recessive Resistance ◽  
Low Concentrations ◽  
Effects Of Temperature ◽  
Resistant Mutants

1. A number of stable nystatin-resistant mutants of the yeastSaccharomyces cerevisiaehave been isolated from platings of a sensitive wild-type strain on low concentrations of the antibiotic.2. These mutants were found to be resistant to 10, 15 or 60 units of drug/ml.3. Analysis of meiotic segregants from crosses of these mutants to wild-type indicate that resistance is determined by two types of genes; resistance genes and modifiers.4. Functional analysis of the mutants demonstrated the existence of three recessive resistance genes,nys-l,nys-2 andnys-3 and thatnys-1 andnys-2 were linked.5. Genetic analysis showed thatnys-1 was affected by two modifiers,Mnys-1 andMnys-2, but that onlyMnys-2 affectednys-2 andnys-3.6. The modifiersMnys-1 andMnys-2 are dominant.7. An investigation of the effects of temperature and medium on resistance demonstrated marked interactions between genotype and environment for both the resistance genes and the modifiers.8. Second-step mutants have been isolated by plating first-step mutants on higher concentrations of the drug. Some of these are resistant to 800 units/ml.9. Some possible mechanisms of nystatin resistance are discussed.

scholarly journals Mechanisms of sod2 Gene Amplification inSchizosaccharomyces pombe

2000 ◽  
Vol 11 (3) ◽  
pp. 873-886 ◽  
Author(s):  
Elizabeth B. Albrecht ◽  
Aaron B. Hunyady ◽  
George R. Stark ◽  
Thomas E. Patterson
Keyword(s):  
Gene Amplification ◽  
Base Pair ◽  
Dna Lesions ◽  
The Novel ◽  
Wild Type ◽  
Resistant Mutants ◽  
Chromosome Ii ◽  
Chromosome I ◽  
Mutant Cells ◽  
Type Strains

Gene amplification in eukaryotes plays an important role in drug resistance, tumorigenesis, and evolution. TheSchizosaccharomyces pombe sod2 gene provides a useful model system to analyze this process. sod2 is near the telomere of chromosome I and encodes a plasma membrane Na+(Li+)/H+ antiporter. Whensod2 is amplified, S. pombe survives otherwise lethal concentrations of LiCl, and >90% of the amplifiedsod2 genes are found in 180- and 225-kilobase (kb) linear amplicons. The sequence of the novel joint of the 180-kb amplicon indicates that it is formed by recombination between homologous regions near the telomeres of the long arm of chromosome I and the short arm of chromosome II. The 225-kb amplicon, isolated three times more frequently than the 180-kb amplicon, is a palindrome derived from a region near the telomere of chromosome I. The center of symmetry of this palindrome contains an inverted repeat consisting of two identical 134-base pair sequences separated by a 290-base pair spacer. LiCl-resistant mutants arise 200–600 times more frequently in strains deficient for topoisomerases or DNA ligase activity than in wild-type strains, but the mutant cells contain the same amplicons. These data suggest that amplicon formation may begin with DNA lesions such as breaks. In the case of the 225-kb amplicon, the breaks may lead to a hairpin structure, which is then replicated to form a double-stranded linear amplicon, or to a cruciform structure, which is then resolved to yield the same amplicon.

scholarly journals Use of the alr Gene as a Food-Grade Selection Marker in Lactic Acid Bacteria

2002 ◽  
Vol 68 (11) ◽  
pp. 5663-5670 ◽  
Author(s):  
Peter A. Bron ◽  
Marcos G. Benchimol ◽  
Jolanda Lambert ◽  
Emmanuelle Palumbo ◽  
Marie Deghorain ◽  
...  
Keyword(s):  
Lactic Acid ◽  
Lactic Acid Bacteria ◽  
Competitive Inhibitor ◽  
Selection Marker ◽  
Wild Type ◽  
Gene Encoding ◽  
Food Grade ◽  
Selection For ◽  
Isogenic Mutants ◽  
Type Strains

ABSTRACT Both Lactococcus lactis and Lactobacillus plantarum contain a single alr gene, encoding an alanine racemase (EC 5.1.1.1), which catalyzes the interconversion of d-alanine and l-alanine. The alr genes of these lactic acid bacteria were investigated for their application as food-grade selection markers in a heterologous complementation approach. Since isogenic mutants of both species carrying an alr deletion (Δalr) showed auxotrophy for d-alanine, plasmids carrying a heterologous alr were constructed and could be selected, since they complemented d-alanine auxotrophy in the L. plantarum Δalr and L. lactis Δalr strains. Selection was found to be highly stringent, and plasmids were stably maintained over 200 generations of culturing. Moreover, the plasmids carrying the heterologous alr genes could be stably maintained in wild-type strains of L. plantarum and L. lactis by selection for resistance to d-cycloserine, a competitive inhibitor of Alr (600 and 200 μg/ml, respectively). In addition, a plasmid carrying the L. plantarum alr gene under control of the regulated nisA promoter was constructed to demonstrate that d-cycloserine resistance of L. lactis is linearly correlated to the alr expression level. Finally, the L. lactis alr gene controlled by the nisA promoter, together with the nisin-regulatory genes nisRK, were integrated into the chromosome of L. plantarum Δalr. The resulting strain could grow in the absence of d-alanine only when expression of the alr gene was induced with nisin.

scholarly journals Engineering multiple species-like genetic incompatibilities in insects

2020 ◽  
Author(s):  
Maciej Maselko ◽  
Nathan Feltman ◽  
Ambuj Upadhyay ◽  
Amanda Hayward ◽  
Siba Das ◽  
...  
Keyword(s):  
Life Stages ◽  
Agricultural Pests ◽  
Wild Type ◽  
Recessive Resistance ◽  
Wild Populations ◽  
Hybrid Lethality ◽  
Multiple Species ◽  
Type Strains ◽  
Gene Drives ◽  
New Strategies

AbstractSpeciation constrains the flow of genetic information between populations of sexually reproducing organisms. Gaining control over mechanisms of speciation would enable new strategies to manage wild populations of disease vectors, agricultural pests, and invasive species. Additionally, such control would provide safe biocontainment of transgenes and gene drives. Natural speciation can be driven by pre-zygotic barriers that prevent fertilization or by post-zygotic genetic incompatibilities that render the hybrid progeny inviable or sterile. Here we demonstrate a general approach to create engineered genetic incompatibilities (EGIs) in the model insect Drosophila melanogaster. Our system couples a dominant lethal transgene with a recessive resistance allele. EGI strains that are homozygous for both elements are fertile and fecund when they mate with similarly engineered strains, but incompatible with wild-type strains that lack resistant alleles. We show that EGI genotypes can be tuned to cause hybrid lethality at different developmental life-stages. Further, we demonstrate that multiple orthogonal EGI strains of D. melanogaster can be engineered to be mutually incompatible with wild-type and with each other. Our approach to create EGI organisms is simple, robust, and functional in multiple sexually reproducing organisms.

Multistress resistance of Saccharomyces cerevisiae is generated by insertion of retrotransposon Ty into the 5' coding region of the adenylate cyclase gene

1988 ◽  
Vol 8 (12) ◽  
pp. 5555-5560
Author(s):  
H Iida
Keyword(s):  
Heat Treatment ◽  
Saccharomyces Cerevisiae ◽  
Heat Shock ◽  
Adenylate Cyclase ◽  
Uv Light ◽  
Yeast Cells ◽  
Wild Type ◽  
Coding Region ◽  
Resistant Mutants ◽  
Type Strains

Heat shock-resistant mutants, which were isolated by their ability to withstand lethal heat treatment, were characterized. Resistance was demonstrated to be a consequence of insertion of retrotransposon Ty into either the 5' coding or noncoding region, close to the putative initiation codon of the adenylate cyclase gene CYR1 (or CDC35). These heat shock-resistant mutants contained about threefold lower adenylate cyclase activity than wild-type strains. The mutants were also observed to be resistant to other stresses such as UV light and ethanol. These results demonstrate that multistress resistance, which may confer a survival advantage to yeast cells, can be generated by transposition of a Ty element into CYR1.

Random environmental variation and inbreeding: effects on pure-strain and hybrid populations of flour beetles (Tribolium)

1986 ◽  
Vol 28 (6) ◽  
pp. 889-898 ◽  
Author(s):  
David Wool ◽  
Orna Bergerson
Keyword(s):  
Environmental Variation ◽  
Single Pair ◽  
Wild Type ◽  
Flour Beetles ◽  
Fitness Trait ◽  
Wild Type Female ◽  
Order Of Magnitude ◽  
Selection For ◽  
Varying Environment ◽  
Type Strains

The effect of inbreeding and of random environmental variation on fitness characters was studied in small populations derived from 10 inbred laboratory strains of Tribolium castaneum (I) and in 18 hybrids (IH) populations, obtained by crossing six mutant to three wild-type strains. Replicate population of each type were held in a constant (C) and a randomly varying (V) environment. Each replicate population was founded by a single pair of adults and one pair of sibs founded each subsequent generation. Thus four groups of inbreeding populations were created: IC, IV, IHC, and IHV. Outbred hybrid populations were held in the varying environment (OV). Several fitness characters were measured. The results confirmed that inbreeding populations exposed to random environmental variation had lower fitness than similar populations in the constant environment populations, as expected (IHC > IHV, IC > IV for each fitness trait). The environmental stress did not result in selection for individuals with higher fitness. In the hybrid populations, consistent and significant differences in fitness between populations having different wild-type (female) ancestors persisted for several generations. No such differences were found among populations grouped by their mutant ancestor. Within each environment, inbreeding had a pronounced effect on fitness. The order of magnitude of the fitness characters was IHC > IC, OV > IHV > IV, parallel to the level of inbreeding. Directional changes in relative (rank) magnitude of fitness characters among populations suggested that their genetic composition was changing temporally.Key words: Tribolium, selection, fitness, inbreedig, population.

scholarly journals Multistress resistance of Saccharomyces cerevisiae is generated by insertion of retrotransposon Ty into the 5' coding region of the adenylate cyclase gene.

1988 ◽  
Vol 8 (12) ◽  
pp. 5555-5560 ◽  
Author(s):  
H Iida
Keyword(s):  
Heat Treatment ◽  
Saccharomyces Cerevisiae ◽  
Heat Shock ◽  
Adenylate Cyclase ◽  
Uv Light ◽  
Yeast Cells ◽  
Wild Type ◽  
Coding Region ◽  
Resistant Mutants ◽  
Type Strains

Heat shock-resistant mutants, which were isolated by their ability to withstand lethal heat treatment, were characterized. Resistance was demonstrated to be a consequence of insertion of retrotransposon Ty into either the 5' coding or noncoding region, close to the putative initiation codon of the adenylate cyclase gene CYR1 (or CDC35). These heat shock-resistant mutants contained about threefold lower adenylate cyclase activity than wild-type strains. The mutants were also observed to be resistant to other stresses such as UV light and ethanol. These results demonstrate that multistress resistance, which may confer a survival advantage to yeast cells, can be generated by transposition of a Ty element into CYR1.

scholarly journals Selection for and against a canalized phenotype in Drosophila melanogaster

1967 ◽  
Vol 10 (1) ◽  
pp. 21-33 ◽  
Author(s):  
S. S. Y. Young
Keyword(s):  
Drosophila Melanogaster ◽  
Lower Proportion ◽  
Modifier Genes ◽  
Wild Type ◽  
Appreciable Change ◽  
Bristle Number ◽  
Alternative Hypotheses ◽  
Males And Females ◽  
Selection For ◽  
Relative Change

Selection for and against the canalized phenotype in scutellar bristles was attempted in two selection lines and a randomly selected line was used as control. The selection lines were the Decanalization line (D) and the Canalization line (N). The D line was maintained by matings of scute males (scwbl) with three scutellars with wild-type females (scwbl/yw) with five bristles, in the N line scute males with four bristles were mated with wild-type females also with four bristles, while in the C line males and females of the above genotypes were selected at random. The lines were established from a sample of flies taken from a line selected for high scutellar numbers.After eighteen generations of selection the C line was characterized by a regression of mean bristle number without appreciable change in variance. Relative to the N line, the D population showed a lower proportion of flies having four scutellars, a higher variance in bristle numbers, and a higher proportion of four-bristle scute flies having abnormal patterns.Two alternative hypotheses were advanced to account for the results of this experiment. The first postulated a relative change in the widths of the four-bristle canalization zones in the selection lines, while the second suggested a relative change in frequencies of specific modifier genes for scutellars in scute and in wild-type genotypes of the lines. The evidence favours the latter hypothesis.

scholarly journals Hydrophilicity of quinolones is not an exclusive factor for decreased activity in efflux-mediated resistant mutants of Staphylococcus aureus.

1996 ◽  
Vol 40 (8) ◽  
pp. 1835-1842 ◽  
Author(s):  
T Takenouchi ◽  
F Tabata ◽  
Y Iwata ◽  
H Hanzawa ◽  
M Sugawara ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Quantitative Structure Activity Relationship ◽  
Wild Type ◽  
Cellular Accumulation ◽  
Structure Activity ◽  
Carbonyl Cyanide ◽  
Elevated Expression ◽  
Resistant Mutants ◽  
Type Strains ◽  
Increment Ratio

The elevated expression of the norA gene is responsible for efflux-mediated resistance to quinolones in Staphylococcus aureus (E.Y.W. Ng, M. Trucksis, and D.C. Hooper, Antimicrob. Agents Chemother. 38:1345-1355, 1994). For S. aureus transformed with a plasmid containing the cloned norA gene, SA113(pTUS20) (H. Yoshida, M. Bogaki, S. Nakamura, K. Ubukata, and M. Konno, J. Bacteriol. 172:6942-6949, 1990), and an overexpressed mutant, SA-1199B (G.W. Kaatz, S.M. Seo, and C.A. Ruble, J. Infect. Dis. 163:1080-1086, 1991), the MICs of norfloxacin increased 16 and 64 times compared with its MICs for the recipient and wild-type strains, SA113 and SA-1199, respectively. MICs of CS-940, however, increased only two and eight times, even though these two fluoroquinolones are similarly hydrophilic (apparent logPs of approximately -1). No good correlation was found, among 15 developed and developing quinolones, between the increment ratio in MICs and hydrophobicity (r = 0.61). Analysis of the quantitative structure-activity relationship among 40 fluoroquinolones revealed that the MIC increment ratio was significantly correlated with the bulkiness of the C-7 substituent and bulkiness and hydrophobicity of the C-8 substituent of fluoroquinolones (r = 0.87) and not with its molecular hydrophobicity (r = 0.47). Cellular accumulation of norfloxacin in SA-1199B was significantly lower than that in SA-1199, and it was increased by addition of carbonyl cyanide m-chlorophenyl hydrazone. On the other hand, accumulations of CS-940 in these strains were nearly identical, and they were not affected by addition of the protonophore.

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