KEY GENE. “In radially symmetrical groups, CYC2 clade members either are not expressed in corolla tissue or are ubiquitously expressed. By contrast, the dorsal restriction of usually two CYC2 paralogues has been found in all bilaterally symmetrical core eudicots to date.”
http://onlinelibrary.wiley.com/doi/10.1111/nph.13198/full