The cloning of the first transcription factor from plants, the CI gene of maize, indicated that plants use transcription factors that are structurally related to those of animals in their control of gene expression because CI showed significant structural homology to the vertebrate cellular proto-oncogene c-MYB Since 1987, the catalogue of MYB-related transcription factors has increased considerably in size due, primarily, to the ever-expanding number of MYB genes identified in higher plants (Arabidopsis thaliana is estimated to contain more than a hundred MYB genes). in vertebrates, the MYB-related proto-oncogenes comprise a small family with a central role in controlling cellular proliferation and commitment to development However, while the functions of some plant MYB genes are relatively well understood they are, at present, quite distinct from their animal counterparts.