title: Two intercellular signals required for fruiting body formation in Myxococcus xanthus act sequentially but non-hierarchically.
abstract: Starvation-induced fruiting body formation in Myxococcus xanthus depends on intercellular signalling. A-signal functions after 2 h of starvation and its synthesis depends on the asg genes. C-signal functions after 6 h of starvation and is generated by proteolytic cleavage of a precursor by the protease PopC. Previous gene expression studies suggested that the A- and C-signal lie on a hierarchical pathway. Here we explored the causal relationship between the A- and C-signal. The asgA and asgB mutants have reduced popC expression, PopC accumulation and C-signal accumulation. popC expression was shown not to depend on A-signal but on the AsgA and AsgB proteins. Restored popC expression in the two mutants rescued PopC and C-signal accumulation as well as C-signalling and the developmental defects of the two mutants without restoring A-signalling. Based on these results we suggest that A- and C-signal do not lie on a hierarchical, dependent pathway. Instead the A- and C-signal act sequentially and without a causal relationship suggesting that they are linked by a shared timing mechanism, which ensures the early and late onset of A-signalling and C-signalling, respectively, during starvation. This pathway topology represents a novel architecture for bacterial intercellular signalling systems involving more than one signal.
authors: Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, Karl-von-Frisch Str. 10, 35043 Marburg, Germany.
authors: Anna
authors: A
authors: Konovalova
authors: Sigrun
authors: S
authors: Wegener-Feldbrügge
authors: Lotte
authors: L
authors: Søgaard-Andersen
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial; D016941:Myxococcus xanthus / Q000235:genetics* / Q000254:growth & development*; D010447:Peptide Hydrolases / Q000235:genetics / Q000378:metabolism; D010770:Phosphotransferases / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction
chemical_list: C086516:AsgB protein, Myxococcus xanthus; D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D010770:Phosphotransferases; C093119:AsgA protein, Myxococcus xanthus; D010447:Peptide Hydrolases