title: Genetic suppression and phenotypic masking of a Myxococcus xanthus frzF- defect.
abstract: An insertion of transposon Tn5-lac, omega 4519, generates a lacZ fusion with a Myxococcus xanthus promoter expressed during both vegetative growth and development. Sequence analysis of the junction of omega 4519 with M. xanthus DNA shows that the insertion is in frzF, a homologue of cheR from Salmonella typhimurium. When frzF- (or frzCD-) cells are starved for nutrients at modest densities, they aggregate to form a radial pattern and produce fewer than 1% of the wild-type complement of spores. At higher densities, frzF::omega 4519 cells form 'frizzy' aggregates and produce 80-90% of the wild-type complement of spores. In contrast, when cells with both a frzF- (or frzCD-) and an sglA1 mutation are allowed to develop at either low or high cell densities, they produce frizzy aggregates containing a near wild-type complement of heat-resistant spores. In addition to suppressing the density dependence of fruiting-body morphogenesis, the sglA1 mutation also suppresses the sporulation defect caused by two different frzF- mutations and a frzCD- mutation. In contrast, a mutation in a different S motility gene, sglG1, does not suppress the frz- mutations. Thus, the suppression of frz- mutations by sgl- mutations is allele-specific, and depends on the sgl allele, but not the frz allele. Because the phenotypes of frz- mutations have been determined in a (suppressing) sglA1 genetic background, the frz genes may play more central roles in development than initially recognized.
authors.affiliation: Department of Microbiology and Molecular Genetics, University of California, Los Angeles 90024-1489, USA.
authors.forename: K
authors.initials: K
authors.lastname: Kashefi
authors.forename: P L
authors.initials: PL
authors.lastname: Hartzell
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D001483:Base Sequence; D002465:Cell Movement; D002633:Chemotaxis; D004251:DNA Transposable Elements / Q000235:genetics; D005798:Genes, Bacterial; D008780:Methyltransferases / Q000172:deficiency* / Q000235:genetics / Q000502:physiology; D008969:Molecular Sequence Data; D009024:Morphogenesis; D016254:Mutagenesis, Insertional; D016941:Myxococcus xanthus / Q000235:genetics* / Q000502:physiology; D009876:Operon / Q000235:genetics; D010641:Phenotype; D013171:Spores, Bacterial; D013489:Suppression, Genetic
chemical_list: D001426:Bacterial Proteins; D004251:DNA Transposable Elements; C065626:FrzCD protein, Myxococcus xanthus; D008780:Methyltransferases; C038706:chemotaxis methyltransferase