SNAPDRAGON MORPHOLOGY. “In A. majus, both paralogues are expressed in the dorsal petals only; however, one copy is more restricted than the other. In other groups, however, the CYC2 expression pattern…has been found. CYC2 genes then activate RAD in the broadest zone of expression. This results in differential expression of DIV, with diffuse expression in dorsal regions and localized epidermal expression in ventral regions. This could result in trichomes developing only in the ventral region.”
http://onlinelibrary.wiley.com/doi/10.1111/nph.13198/full