GENE CASCADE. “In the absence of RAD, DIVARICATA (DIV) localizes to the surface epidermal cells where it may up-regulate AmMYBL1 (a MIXTA-like gene), resulting (at least in Antirrhinum majus) in trichome formation throughout the corolla tube.”
http://onlinelibrary.wiley.com/doi/10.1111/nph.13198/full