act operon control of developmental gene expression in Myxococcus xanthus.
Cell-bound C-signal guides the building of a fruiting body and triggers the differentiation of myxospores. Earlier work has shown that transcription of the csgA gene, which encodes the C-signal, is directed by four genes of the act operon. To see how expression of the genes encoding components of the aggregation and sporulation processes depends on C-signaling, mutants with loss-of-function mutations in each of the act genes were investigated. These mutations were found to have no effect on genes that are normally expressed up to 3 h into development and are C-signal independent. Neither the time of first expression nor the rate of expression increase was changed in actA, actB, actC, or actD mutant strains. Also, there was no effect on A-signal production, which normally starts before 3 h. By contrast, the null act mutants have striking defects in C-signal production. These mutations changed the expression of four gene reporters that are related to aggregation and sporulation and are expressed at 6 h or later in development. The actA and actB null mutations substantially decreased the expression of all these reporters. The other act null mutations caused either premature expression to wild-type levels (actC) or delayed expression (actD), which ultimately rose to wild-type levels. The pattern of effects on these reporters shows how the C-signal differentially regulates the steps that together build a fruiting body and differentiate spores within it.
Gronewold
Thomas M A
TM
Departments of Biochemistry and of Developmental Biology, Stanford University School of Medicine, Stanford, California 94305-5329, USA.
Kaiser
Dale
D
D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D018507:Gene Expression Regulation, Developmental; D008565:Membrane Proteins / Q000235:genetics*; D016941:Myxococcus xanthus / Q000235:genetics*; D009876:Operon; D010770:Phosphotransferases
D001426:Bacterial Proteins; C063576:CsgA protein, Myxococcus xanthus; D008565:Membrane Proteins; C072980:actA protein, Listeria monocytogenes; D010770:Phosphotransferases; C093119:AsgA protein, Myxococcus xanthus