Mutations in Ophiostoma ulmi induced by N-methyl-N′-nitro-N-nitrosoguanidine

1990 ◽  
Vol 68 (2) ◽  
pp. 225-231 ◽  
Author(s):  
L. Bernier ◽  
M. Hubbes
Keyword(s):  
Dutch Elm Disease ◽  
Recessive Mutation ◽  
Wild Type ◽  
Ophiostoma Ulmi ◽  
Cell Age ◽  
Disease Mutations ◽  
Nuclear Locus ◽  
Type Strains ◽  
Yeastlike Cells ◽  
Incubation Buffer

Mutations were induced in Ophiostoma ulmi, the causal agent of Dutch elm disease, by treating yeastlike cells of wild-type strains with the alkylating agent N-methyl-N′-nitro-N-nitrosoguanidine (MNNG). The induced frequency of mutation, assessed by scoring the frequency of benomyl-resistant mutants among the surviving population, was highest in treatments that left from 4 to 10% survivors. The survival rate of the cells was affected by mutagen concentration and length of exposure to MNNG, as well as by cell concentration, cell age, pH, and chemical composition of the incubation buffer. Optimal conditions for routine induction of mutants were obtained by resuspending exponentially growing cultures in phosphate buffer at pH 7.5 (2.0 × 107 cells/mL) and treating the cells with MNNG (20 μg/mL) for 90 min with agitation. The proportion of auxotrophs among the survivors increased at least 200-fold when mutagenesis was followed by nystatin enrichment. Most auxotrophs tested were sexually fertile and carried a recessive mutation at a single nuclear locus. The benomyl-resistant phenotype was dominant. Key words: Ophiostoma ulmi, Dutch elm disease, mutations, N-methyl- N′-nitro-N-nitrosoguanidine.

scholarly journals NUCLEAR MUTATION INCREASES STREPTOMYCIN AND SPECTINOMYCIN SENSITIVITY IN CHLAMYDOMONAS

Genetics ◽  
1978 ◽  
Vol 88 (4) ◽  
pp. 643-650
Author(s):  
Robert W Lee ◽  
Jan A Sapp
Keyword(s):  
Large Subunit ◽  
Small Subunit ◽  
Wild Type ◽  
Resistance Mutations ◽  
Erythromycin Resistance ◽  
Spectinomycin Resistance ◽  
Nuclear Mutation ◽  
Resistant Strains ◽  
Nuclear Locus ◽  
Type Strains

ABSTRACT A spontaneously arising nuclear mutation, ss-1, has been identified in Chlamydomonas reinhardtii that decreases both streptomycin and spectinomycin resistance levels about 10-fold after its introduction into all wild-type, streptomycin-resistant and spectinomycin-resistant strains examined. The mutations for resistance map to nuclear and uniparentally inherited (chloroplast) loci. In contrast, no modification of erythromycin resistance was detected after introducing ss-1 into wild-type strains or into strains carrying nuclear or uniparentally inherited erythromycin-resistance mutations. We suggest that ss-1 affects the small subunit of the chloroplast ribosome because others have shown that streptomycin and spectinomycin resistance in C. reinhardtii are associated with this subunit, whereas erythromycin resistance is associated with the large subunit. ss-1 shows no linkage with the nuclear locus for streptomycin resistance.

scholarly journals SELECTIVE ABORTION OF TWO NONSISTER NUCLEI IN A DEVELOPING ASCUS OF THE hfd1—1 MUTANT IN SACCHAROMYCES CEREVISIAE

Genetics ◽  
1981 ◽  
Vol 99 (2) ◽  
pp. 197-209
Author(s):  
Susumu Okamoto ◽  
Tetsuo Iino
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Mutant Strain ◽  
Recessive Mutation ◽  
Microscopical Examination ◽  
Wild Type ◽  
Selective Abortion ◽  
Dyad Analysis ◽  
Mutant Cells ◽  
Type Strains ◽  
Light Microscopical Examination

ABSTRACT A recessive mutation, hfd1—1, in strain SOS4 of Saccharomyces cerevisiae leads the mutant cells to produce predominantly two-spored asci. Light microscopical examination of Giemsastained cells revealed no significant differences in the meiotic figures between mutant and wild-type strains. However, only two of the four meiotic products in a developing ascus matured to ascospores in SOS4. Dyad analysis was carried out on an hfd1-1 mutant strain heterozygous for three markers, asp5, gal1 and arg4, which are closely linked to their centromeres, and for his4, which is loosely linked to its centromere. The twospored asci produced by the hfd1—1 mutant segregated dominant (+) and recessive (-) alleles of each marker in a 1:1 ratio; they generally contained one + and one - spore for any given marker. The occurrence of rare dyads with two + or two - spores can be explained quantitatively by recombination between the marker and its centromere. From the results of these cytological and genetical analyses, we infer that, in the mutant strain, one genome set is partitioned to each of the four second-meiotic division poles, but only two nonsister genomes are incorporated into mature spores. Thus, the hfd1—1 mutation in SOS4 blocks incorporation of two nonsister nuclei into mature ascospores, but does not block enclosure of the remaining two nonsister nuclei.

Meiotic analysis of induced mutations in Ophiostoma ulmi

1990 ◽  
Vol 68 (2) ◽  
pp. 232-235 ◽  
Author(s):  
L. Bernier ◽  
M. Hubbes
Keyword(s):  
Linkage Group ◽  
Dutch Elm Disease ◽  
Induced Mutations ◽  
Type Locus ◽  
Meiotic Analysis ◽  
Ophiostoma Ulmi ◽  
Group I ◽  
Disease Mutations ◽  
Nuclear Mutations ◽  
Additional Locus

Laboratory strains of Ophiostoma ulmi carrying nuclear mutations induced by exposure to N-methyl-N′-nitro-N-nitrosoguanidine were crossed, and the segregation of genetic markers was analyzed in random ascospore progeny. Investigation of 13 auxotrophic mutations and 1 benomyl-resistant mutation provided evidence for at least three linkage groups in O. ulmi. Five loci, identified by mutant alleles ade1-1, BENIR-1, cyi1-1, lys3-1, and nic1-1, were assigned to linkage group I, whereas markers ade2-1 and lys2-2 were mapped on linkage group II. An additional locus, Met1, was assigned to a third linkage group since mutant alleles at this locus segregated independently from markers on group I or II. The Ben1R locus, controlling resistance to benomyl, segregated independently from the mating type locus and thus appeared to differ from the Tol locus described by other workers. Key words: Ophiostoma ulmi, Dutch elm disease, mutations, linkage analysis.

Nonsporulation in the Dutch elm disease fungus Ophiostoma ulmi: evidence for control by a single nuclear gene

1994 ◽  
Vol 72 (4) ◽  
pp. 461-467 ◽  
Author(s):  
Wayne C. Richards
Keyword(s):  
Key Words ◽  
Genetic Control ◽  
Genetic Stability ◽  
Nuclear Gene ◽  
Dutch Elm Disease ◽  
Wild Type ◽  
Ulmus Americana ◽  
Disease Symptoms ◽  
Ophiostoma Ulmi ◽  
Yeast Phase

A single nuclear gene controls nonsporulation in a novel isolate of the Dutch elm disease fungus Ophiostoma ulmi (Buism.) Nannf. This has been clearly demonstrated through segregation of the nonsporulating phenotype-in meiotic products recovered from crosses between a mutant nonsporulating isolate (WRB2-1) and wild-type sporulating isolates, between F1 progeny and their parents, and between F1 progeny. All crosses between nonsporulating and sporulating isolates yielded a 1:1 ratio for these two phenotypes in the meiotic products, whereas all crossings between isolates of the same phenotype produced meiotic products of that phenotype. The genetic stability of the nonsporulating phenotype was clearly shown when no disease symptoms were observed following artificial inoculation of the nonsporulating progeny into white elm, Ulmus americana L. Exposure to trifluoperazine, a calmodulin inhibitor, did not shift the nonsporulating isolates to the yeast phase, which supports our findings that nonsporulation is under genetic control rather than metabolic control. Key words: nonsporulation, Ophiostoma ulmi, mutant, single nuclear gene, meiotic products.

scholarly journals Identification ofvib-1, a Locus Involved in Vegetative Incompatibility Mediated byhet-cinNeurospora crassa

Genetics ◽  
2002 ◽  
Vol 162 (1) ◽  
pp. 89-101 ◽  
Author(s):  
Qijun Xiang ◽  
N Louise Glass
Keyword(s):  
Acid Phosphatase ◽  
Recognition System ◽  
Deletion Mutants ◽  
Wild Type ◽  
Vegetative Incompatibility ◽  
Death Rates ◽  
Self Recognition ◽  
Allelic Differences ◽  
Native Gel ◽  
Type Strains

AbstractA non-self-recognition system called vegetative incompatibility is ubiquitous in filamentous fungi and is genetically regulated by het loci. Different fungal individuals are unable to form viable heterokaryons if they differ in allelic specificity at a het locus. To identify components of vegetative incompatibility mediated by allelic differences at the het-c locus of Neurospora crassa, we isolated mutants that suppressed phenotypic aspects of het-c vegetative incompatibility. Three deletion mutants were identified; the deletions overlapped each other in an ORF named vib-1 (vegetative incompatibility blocked). Mutations in vib-1 fully relieved growth inhibition and repression of conidiation conferred by het-c vegetative incompatibility and significantly reduced hyphal compartmentation and death rates. The vib-1 mutants displayed a profuse conidiation pattern, suggesting that VIB-1 is a regulator of conidiation. VIB-1 shares a region of similarity to PHOG, a possible phosphate nonrepressible acid phosphatase in Aspergillus nidulans. Native gel analysis of wild-type strains and vib-1 mutants indicated that vib-1 is not the structural gene for nonrepressible acid phosphatase, but rather may regulate nonrepressible acid phosphatase activity.

scholarly journals HET-E and HET-D Belong to a New Subfamily of WD40 Proteins Involved in Vegetative Incompatibility Specificity in the Fungus Podospora anserina

Genetics ◽  
2002 ◽  
Vol 161 (1) ◽  
pp. 71-81
Author(s):  
Eric Espagne ◽  
Pascale Balhadère ◽  
Marie-Louise Penin ◽  
Christian Barreau ◽  
Béatrice Turcq
Keyword(s):  
Genetic Difference ◽  
Podospora Anserina ◽  
Wild Type ◽  
Incompatible Interaction ◽  
Vegetative Incompatibility ◽  
Repeat Domain ◽  
Upper Face ◽  
E1a Gene ◽  
Type Strains ◽  
Wd40 Repeats

Abstract Vegetative incompatibility, which is very common in filamentous fungi, prevents a viable heterokaryotic cell from being formed by the fusion of filaments from two different wild-type strains. Such incompatibility is always the consequence of at least one genetic difference in specific genes (het genes). In Podospora anserina, alleles of the het-e and het-d loci control heterokaryon viability through genetic interactions with alleles of the unlinked het-c locus. The het-d2Y gene was isolated and shown to have strong similarity with the previously described het-e1A gene. Like the HET-E protein, the HET-D putative protein displayed a GTP-binding domain and seemed to require a minimal number of 11 WD40 repeats to be active in incompatibility. Apart from incompatibility specificity, no other function could be identified by disrupting the het-d gene. Sequence comparison of different het-e alleles suggested that het-e specificity is determined by the sequence of the WD40 repeat domain. In particular, the amino acids present on the upper face of the predicted β-propeller structure defined by this domain may confer the incompatible interaction specificity.

scholarly journals Isolation of a gene required for programmed initiation of development by Aspergillus nidulans.

1992 ◽  
Vol 12 (9) ◽  
pp. 3827-3833 ◽  
Author(s):  
T H Adams ◽  
W A Hide ◽  
L N Yager ◽  
B N Lee
Keyword(s):  
Life Cycle ◽  
Aspergillus Nidulans ◽  
Optimal Growth ◽  
Growth Conditions ◽  
Nutrient Deprivation ◽  
Deletion Mutants ◽  
Wild Type ◽  
Microbial Development ◽  
Type Strains ◽  
Posttranscriptional Level

In contrast to many other cases in microbial development, Aspergillus nidulans conidiophore production initiates primarily as a programmed part of the life cycle rather than as a response to nutrient deprivation. Mutations in the acoD locus result in "fluffy" colonies that appear to grow faster than the wild type and proliferate as undifferentiated masses of vegetative cells. We show that unlike wild-type strains, acoD deletion mutants are unable to make conidiophores under optimal growth conditions but can be induced to conidiate when growth is nutritionally limited. The requirement for acoD in conidiophore development occurs prior to activation of brlA, a primary regulator of development. The acoD transcript is present both in vegetative hyphae prior to developmental induction and in developing cultures. However, the effects of acoD mutations are detectable only after developmental induction. We propose that acoD activity is primarily controlled at the posttranscriptional level and that it is required to direct developmentally specific changes that bring about growth inhibition and activation of brlA expression to result in conidiophore development.

scholarly journals Influences of Histone Stoichiometry on the Target Site Preference of Retrotransposons Ty1 and Ty2 in Saccharomyces cerevisiae

Genetics ◽  
1996 ◽  
Vol 142 (3) ◽  
pp. 761-776 ◽  
Author(s):  
Lori A Rinckel ◽  
David J Garfinkel
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Promoter Region ◽  
Target Site ◽  
Site Preference ◽  
Wild Type ◽  
Histone Proteins ◽  
Protein Levels ◽  
In The Wild ◽  
Type Strains ◽  
Orientation Bias

Abstract In Saccharomyces cerevisiae, the target site specificity of the retrotransposon Ty1 appears to involve the Ty integration complex recognizing chromatin structures. To determine whether changes in chromatin structure affect Ty1 and Ty2 target site preference, we analyzed Ty transposition at the CAN1 locus in mutants containing altered levels of histone proteins. A Δhta1-htb1 mutant with decreased levels of H2A and H2B histone proteins showed a pattern of Ty1 and Ty2 insertions at CAN1 that was significantly different from that of both the wild-type and a Δhta2-htb2 mutant, which does not have altered histone protein levels. Altered levels of H2A and H2B proteins disrupted a dramatic orientation bias in the CAN1 promoter region. In the wild-type strains, few Ty1 and Ty2 insertions in the promoter region were oriented opposite to the direction of CAN1 transcription. In the Δhta1-htb1 background, however, numerous Ty1 and Ty2 insertions were in the opposite orientation clustered within the TATA region. This altered insertion pattern does not appear to be due to a bias caused by selecting canavanine resistant isolates in the different HTA1-HTB1 backgrounds. Our results suggest that reduced levels of histone proteins alter Ty target site preference and disrupt an asymmetric Ty insertion pattern.

Development of mutants of Gliocladium virens tolerant to benomyl

1990 ◽  
Vol 36 (7) ◽  
pp. 484-489 ◽  
Author(s):  
G. C. Papavizas ◽  
D. P. Roberts ◽  
K. K. Kim
Keyword(s):  
Carbon Source ◽  
Type Strain ◽  
Wild Type Strain ◽  
Carbon Sources ◽  
Sclerotium Rolfsii ◽  
Wild Type ◽  
Gliocladium Virens ◽  
Rhizosphere Competence ◽  
Filter Paper Cellulase ◽  
Type Strains

Aqueous suspensions of conidia of Gliocladium virens strains Gl-3 and Gl-21 were exposed to both ultraviolet radiation and ethyl methanesulfonate. Two mutants of Gl-3 and three of Gl-21 were selected for tolerance to benomyl at 10 μg∙mL−1, as indicated by growth and conidial germination on benomyl-amended potato dextrose agar. The mutants differed considerably from their respective wild-type strains in appearance, growth habit, sporulation, carbon-source utilization, and enzyme activity profiles. Of 10 carbon sources tested, cellobiose, xylose, and xylan were the best for growth, galactose and glucose were intermediate, and arabinose, ribose, and rhamnose were poor sources of carbon. The wild-type strains and the mutants did not utilize cellulose as the sole carbon source for growth. Two benomyl-tolerant mutants of Gl-3 produced less cellulase (β-1,4-glucosidase, carboxymethylcellulase, filter-paper cellulase) than Gl-3. In contrast, mutants of Gl-21 produced more cellulase than the wild-type strain. Only Gl-3 provided control of blight on snapbean caused by Sclerotium rolfsii. Wild-type strain Gl-21 and all mutants from both strains were ineffective biocontrol agents. Key words: Gliocladium, benomyl tolerance, Sclerotium, rhizosphere competence.

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