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Two intercellular signals required for fruiting body formation in Myxococcus xanthus act sequentially but non‐hierarchically
Author(s) -
Konovalova Anna,
WegenerFeldbrügge Sigrun,
SøgaardAndersen Lotte
Publication year - 2012
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2012.08173.x
Subject(s) - myxococcus xanthus , biology , popc , mutant , microbiology and biotechnology , signal transduction , intracellular , signalling , gene , biochemistry , vesicle , membrane
Summary 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.