title: Suppressor mutants of Neurospora crassa that tolerate allelic differences at single or at multiple heterokaryon incompatibility loci.
abstract: Allelic differences at any one of at least 11 heterokaryon incompatibility (het) loci in Neurospora crassa trigger an incompatibility response: localized cell death at sites of hyphal anastomosis. We have isolated spontaneous and insertional suppressor mutants that are heterokaryon-compatible in spite of allelic differences at one or at several het loci. Some intra- and extragenic mutants tolerated allelic differences only at single het loci. Multi-tolerant spontaneous mutants were isolated by selecting simultaneously for tolerance of differences at het-c, -d and -e, or at each of these plus mating-type. Some suppressor mutants were specific for only one allele at the affected het locus; others suppressed both alleles. Insertional mutations were isolated from banks of transformants, each having a plasmid integrated into a random position in the chromosome. One mutant tolerated allelic differences at het-d. A homologous cosmid from a Neurospora genomic bank complemented the mutant phenotype. A second insertional inactivation mutant was tolerant of het-c differences. Inactivation of the wild-type locus corresponding to the integration site was accomplished by repeat-induced point mutation (RIP). The RIP progeny, like the original mutant, were tolerant of differences at het-c. It may be possible to use such suppressor mutants as universal donors of hypovirulence in pathogenic fungi.
authors.affiliation: Wayne State University School of Medicine, Department of Biochemistry, Detroit, Michigan 48201.
authors.forename: M T
authors.initials: MT
authors.lastname: Arganoza
authors.forename: J
authors.initials: J
authors.lastname: Ohrnberger
authors.forename: J
authors.initials: J
authors.lastname: Min
authors.forename: R A
authors.initials: RA
authors.lastname: Akins
mesh_terms: D000483:Alleles; D002459:Cell Fusion; D015825:Chromosomes, Fungal; D003433:Crosses, Genetic; D005800:Genes, Fungal; D049770:Genes, Mating Type, Fungal; D016153:Genes, Suppressor; D005816:Genetic Complementation Test; D005838:Genotype; D016254:Mutagenesis, Insertional; D009492:Neurospora crassa / Q000235:genetics* / Q000502:physiology; D010641:Phenotype; D017354:Point Mutation; D012100:Reproduction, Asexual; D013172:Spores, Fungal / Q000502:physiology; D013489:Suppression, Genetic