The interaction diagram of the GRN underlying cell type determination in the root stem cell niche of the model plant A. thaliana. The abbreviated names of the genes are inside ellipses and the edges correspond to the regulatory interactions. Auxin is a morphogene. The genes are: Auxin/INDOLE-3-ACETIC ACID (Aux/IAA), AUXIN RESPONSE FACTOR (ARF), JACKDAW (JKD), MAGPIE (MGP), PLETHORA (PLT), SCARECROW (SCR), SHORTROOT (SHR), and WUSCHEL-RELATED HOMEBOX5 (WOX5). Ordinary arrow heads denote activation; T-bar arrow heads denote inhibition.