Six genes that contain sequence encoding the DNA binding domain of the Myb oncoproteins have been isolated from a cDNA library prepared from Antirrhinum majus (snapdragon) flowers using oligonucleotide probes directed against part of this domain. The derived amino acid sequences of these genes reveal acidic domains in their carboxy termini, suggesting that they might act as transcriptional activators. Analysis of their expression patterns with respect to organ specificity, floral differentiation, and response to light suggests that these genes are not involved in controlling anthocyanin biosynthesis, unlike the characterized myb-related genes C1 and Pl from maize. One of the genes is expressed mainly in the nectary and the transmitting tract of the style, two major secretory tissues of the flower, suggesting that the function of this gene is related to active carbohydrate secretion. We conclude that plants contain a number of myb-related transcriptional activators involved in a diversity of gene regulation.