title: C-factor has distinct aggregation and sporulation thresholds during Myxococcus development.
abstract: C-factor, the protein product of the csgA gene, acts as a short-range morphogenetic signal. It is required for fruiting body development of the gram-negative bacterium Myxococcus xanthus. Aggregation, sporulation, and expression of a set of genes that are C-factor dependent, all of which fail in csgA mutant cells, are completely restored by addition of purified C-factor. We report here that, depending on its concentration, C-factor can elicit two distinct morphogenetic and transcriptional responses from csgA cells. Low levels of C-factor bring about aggregation and expression of an early C-dependent gene, whereas higher levels lead to the same effects plus expression of a late C-dependent gene and spore formation. C-factor positively regulates its own transcription. An approximately fourfold net increase in csgA transcription and C-factor levels during development was measured. We propose that autoregulation and the two distinct activity thresholds allow C-factor to act as a timer, first triggering aggregation, then sporulation, thereby producing the appropriate developmental order.
authors.affiliation: Department of Biochemistry, Stanford University School of Medicine, California 94305.
authors.forename: S K
authors.initials: SK
authors.lastname: Kim
authors.forename: D
authors.initials: D
authors.lastname: Kaiser
mesh_terms: D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D004251:DNA Transposable Elements; D007700:Kinetics; D009231:Myxococcales / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D013171:Spores, Bacterial / Q000502:physiology; D014158:Transcription, Genetic; D001616:beta-Galactosidase / Q000096:biosynthesis / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; C063576:CsgA protein, Myxococcus xanthus; D004251:DNA Transposable Elements; D011993:Recombinant Fusion Proteins; D001616:beta-Galactosidase