Represses the transcription of the sdpIR operon and of several other operons that probably contribute to delaying commitment to sporulation. Sequestred at the bacterial membrane by SdpC-bound SdpI. By Spo0A during nutrient starvation through its direct negative control of AbrB, repressed by AbrB during regular growth when nutrients are plentiful (PubMed:16469701). Represses its own transcription (PubMed:16469701). Induced by expression of SDP (active peptide of sdpC) (PubMed:16469701, PubMed:23687264).