However for stage 2 to be activated, several more things have to be satisfied: "this transition depends on the synthesis of an efficient histidine kinase (KinA), on an increased rate of synthesis of Spo0A, and on the neutralization of various antagonists of the phosphorelay and repressors of Spo0A-dependent genes."
"The combined effects of releasing repression by AbrB and CodY, and of activating σH (?), the product of spo0H, lead to induction of kinA, spo0F and spo0A (from σH-dependent promoters) and the potential to produce a higher level of Spo0A~P"
σH is a specific form of RNA Polymerase required for sufficient synthesis levels of Spo0A, Spo0F and kinA
"The sporulation promoters of spo0A and spo0F, as well as the kinA promoter, depend on the σH form of RNA polymerase."
"spo0H, the gene that encodes σH, is repressed by AbrB and is, therefore, expressed very poorly in cells at low population density. Thus, since Spo0A represses abrB and AbrB represses spo0H, Spo0A~P is an indirect autoinducer <of the σH form of RNA polymerase>"
"Turning on the kinA gene is not by itself sufficient to push a stationary phase cell toward the sporulation pathway"
because
There are many repressors that act as a checkpoint at this stage of sporulation (remember that sporulation is an 8 hour process that is incredibly energy intensive and so should ONLY be undertaken if absolutely necessary) e.g "while the cell is accumulating KinA, it is also accumulating Spo0F~P phosphatases (Rap proteins) and a Spo0A~P phosphatase (Spo0E)"