Figure 8.

A Model Showing the Double Positive Autoregulatory Feedback Loop Evolved in the P. heterotricha CYC1 Genes.

After expression initiation, CYC1C (blue box) and CYC1D (orange box) genes maintain expression throughout floral development via a double positive autoregulatory feedback loop by forming both homo- and heterodimers. The blue and orange circles represent the CYC1C and CYC1D proteins, and the blue and orange ovals represent the CYC binding sites found in the CYC1C and CYC1D promoters, respectively.