Petunia flowers demonstrating cosuppression

(a) The wild-type (no transgene) phenotype. (b and c) So-called cosuppression phenotypes resulting from the transformation of the wild-type petunia shown in part a with a petunia gene required for pigmentation. In the colorless regions, both the transgene and the chromosomal copy of the same gene have been inactivated.

[Richard Jorgensen, Department of Plant Biology, Carnegie Institution for Science]