FIG. 4.

Regulation scheme of the S. meliloti flagellar, motility, and chemotaxis gene system falling into a hierarchy of three expression classes. The transcription polarities of operons and flaA are indicated by horizontal arrows drawn below the gene symbols (33). Translation to gene products (ellipsoids) is indicated by open white arrows, and positive regulatory controls are indicated by solid arrows. The postulated heterodimeric structure of VisNR, posttranslational activation by an unknown effector, and subclassification of basal-body (IIA) and motor (IIB) genes are included.