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1.
Fungal Genet Biol ; 32(3): 183-93, 2001 Apr.
Article in English | MEDLINE | ID: mdl-11343404

ABSTRACT

The cAMP signal transduction pathway mediates the switch between yeast-like and filamentous growth and influences both sexual development and pathogenicity in the smut fungus Ustilago maydis. Signaling via cAMP may also play a role in fungicide resistance in U. maydis. In particular, the adr1 gene, which encodes the catalytic subunit of the U. maydis cAMP-dependent protein kinase (PKA), is implicated in resistance to the dicarboximide and aromatic hydrocarbon fungicides. In this study, we examined the sensitivity of PKA to vinclozolin and could not demonstrate direct inhibition of protein kinase activity. However, we did find that mutants with disruptions in the ubc1 gene, which encodes the regulatory subunit of PKA, were resistant to both vinclozolin and chloroneb. We also found that these fungicides altered the morphology of both wild-type and ubc1 mutant cells. In addition, strains that are defective in ubc1 display osmotic sensitivity, a property often associated with vinclozolin and chloroneb resistance in other fungi.


Subject(s)
Cyclic AMP/metabolism , Fungicides, Industrial/pharmacology , Hydrocarbons, Aromatic/pharmacology , Oxazoles/pharmacology , Signal Transduction , Ustilago/drug effects , Chlorobenzenes/pharmacology , Cyclic AMP-Dependent Protein Kinases/genetics , Cyclic AMP-Dependent Protein Kinases/metabolism , Drug Resistance, Microbial , Gene Expression Regulation, Fungal , Imides/pharmacology , Ustilago/growth & development
2.
Chromosoma ; 104(3): 189-202, 1995 Nov.
Article in English | MEDLINE | ID: mdl-8529459

ABSTRACT

We have characterized the phenotypes of three rad12 mutants of the basidiomycete Coprinus cinereus, which were isolated on the basis of sensitivity to ionizing radiation. Electron microscopic studies of meiotic nuclear spreads showed that all three rad12 mutants are defective in chromosomal synapsis. For rad12-1 and rad12-4, very limited assembly of the synaptonemal complex occurs. The phenotype of rad12-15 is less severe and longer stretches of synapsed chromosomes are formed. However, for all three alleles mutant nuclei arrest in a diffuse state with little synaptonemal complex structure. Observations made of spreads of acridine orange-stained meiotic nuclei correlated with the electron microscopic data. In rad12 strains, chromosomes condense but do not pair, and they later arrest in a decondensed state; very few rad12 cells enter metaphase I. Homozygous dikaryons of rad12 mutants produce fruiting bodies with significantly fewer basidiospores than are found in wild-type dikaryons. The viability of these spores is greatly reduced: all spores produced by rad12-1 and rad12-4 mushrooms fail to germinate, while only 16% of rad12-15 spores are viable. Recombination within the tract of the ribosomal RNA gene repeats was not significantly different in the mutants when compared with a wild-type congenic control. Quantitative measurements of oidial survival indicate that all three rad12 alleles are sensitive to gamma radiation but insensitive to UV radiation relative to wild-type strains.


Subject(s)
Chromosomes, Fungal/ultrastructure , Coprinus/genetics , Fungal Proteins/genetics , Genes, Fungal , Cell Nucleus/physiology , Cell Nucleus/ultrastructure , Cesium Radioisotopes , Coprinus/radiation effects , Coprinus/ultrastructure , Crosses, Genetic , Dose-Response Relationship, Radiation , Gamma Rays , Genes, Fungal/radiation effects , Genotype , Meiosis , Mutation , Phenotype , Radiation, Ionizing , Species Specificity , Ultraviolet Rays
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