FIG 2.

The hormogonium gene regulatory network. Various chemical signals influence the initiation of hormogonium development through unknown means. The hybrid histidine kinase HrmX is the earliest known actor in the GRN and is presumed to regulate the phosphorylation state of an unknown response regulator which in turn directly activates expression of some hormogonium-specific genes while indirectly activating others via the initiation of the sigma-factor cascade, leading to the development of motile hormogonia. Black arrows indicate positive transcriptional regulation. Black lines with bars indicate negative transcriptional regulation. Purple arrow indicates posttranscriptional regulation. Thickness of lines represents an approximation of the strength of regulation, or the number of genes regulated within a functional category (e.g., Cell Division).