Fig 1. Gene regulatory network of heterocyst differentiation.

The main elements involved and their interactions for heterocyst differentiation are depicted schematically together with other relevant genes (light red rectangles) not included in our model. Rectangles, circles, and polyhedric forms represent genes, inactive proteins, and active products, respectively. AHetR stands for the active form of HetR. The ellipse represents differentiation into a heterocyst. Arrows with solid lines represent interactions between elements. Arrows with dashed-dotted lines represent post-transcriptional changes. The dashed line represents a simplified interaction of nitrogen sensing through ntcA. References justifying these interactions are incorporated. Regular and bold formatted references indicate phenotypically inferred and observed molecular interactions, respectively.