Fig. 9.

A model showing the proposed regulation of pknE and HetR in differentiating cells. The hetR gene is initially upregulated in differentiating cells and shows positive autoregulation. During the early phase of differentiation, HetR upregulates the expression of pknE. We propose that increased PknE activity during middle or late stages of heterocyst differentiation negatively regulates HetR abundance or activity, which may be required for normal heterocyst differentiation. Arrows indicate positive regulation, and the bar indicates negative regulation.