SinR Pre-sporulation stage - the vegetative state of B. subtilis cells
SinR in the vegetative state
The sin (sporulation inhibition) operon plays a key role in the timing and early development of sporulation initiation when cells gradually exit vegetative growth and enter the stationary phase. Before this point, the second gene in the operon (sinR) is constitutively expressed by an internal σA -dependent promoter (P3) producing the repressor protein SinR 17. This protein is described as the master regulator involved in biofilm formation 17, but is also known to inhibit the sporulation process 19. It does so by binding to the DNA directly upstream important early sporulation genes, such as spoIIA 20, spo0A and genes encoding sporulation-specific sigma factors 21, 22. The first gene in the operon (sinI) is not expressed during vegetative state because activity of its two upstream promoters is blocked by repressor proteins ScoC, AbrB and SinR 14, 23.