Transcriptional regulator that controls expression of some virulence factors in a cell density-dependent manner. Expressed at the early exponential growth phase, decreases through exponential phase and reaches a steady-state level at post-exponential phase. Repressed by MgrA and SarA. Activated by Rot and SarT. Transcription is also dependent on SigA and SigB factors. Is activated by SigB in strains harboring an intact sigB operon (rsbU, rsbV, rsbW, and sigB) (By similarity). Belongs to the SarA family.