GENE MODULE INTERACTIONS. “Finally, different modules of regulatory networks can interact differently across the tree of life. For example, in Pisum sativum conical cells occur only on petals with CYC2 expression and are lost when CYC2 expression is lost, implying a developmental constraint within this network that could be relaxed in other taxa.”
http://onlinelibrary.wiley.com/doi/10.1111/nph.13198/full