A novel myb-like gene (Atmyb5) has been isolated from a genomic library of Arabidopsis thaliana. The gene contains a single intron in the region coding for the Myb domains. The Myb domains are highly homologous to other animal and plant Myb proteins. Arabidopsis plants transgenic for a chimeric Atmyb5 promoter/GUS gene expressed the enzyme in a developmentally controlled and tissue specific manner. The GUS activity was detected in developing leaf trichomes, stipules, epidermal cells on the margins of young rosette and cauline leaves, and in immature seeds. Atmyb5 mRNA appears between fertilization and the 16 cell stage of embryo development and persists beyond the heart stage.