Model of Ath5 expression dynamics. Summary of input on the 3-kb Ath5 promoter fragment. Solid lines represent activities that were confirmed in vivo, and shaded solid lines represent regulatory activities that were not significant in vivo. (a) Onset of Ath5 expression. Group 1 genes such as MCM2 and KPNA4 may act to prevent premature Ath5 expression. Ath5 expression is switched on by group 2 genes, such as sFRP1 and Rb. (b) Downregulation of Ath5. Group 3 genes: Ndrg3 and Islet-2 may prevent premature downregulation of Ath5. Expression of Ath5 is downregulated by signals through Idax and the regulatory activity of RBPMS2, ELG-protein and Zfp-161 (group 4).