SYMMETRIC GENE EXPRESSION. “In radially symmetrical flowers, expression of CYCLOIDEA2 (CYC2) genes have been shown to be either not expressed or ubiquitously expressed. When CYC2 is not expressed, RADIALIS (RAD) is no longer activated.” (See Figure 1).
http://onlinelibrary.wiley.com/doi/10.1111/nph.13198/full