Dof proteins are members of a major family of plant transcription factors. The proteins have similar DNA-binding properties because of the highly conserved DNA-binding domain. However, recent studies are disclosing their diverse roles in gene expression when associated with plant-specific phenomena including light, phytohormone and defense responses, seed development and germination. Based on the structural diversity indicated by the complete catalog of Arabidopsis Dof proteins, Dof genes appear to have evolved multiple times, preceding and paralleling the diversification of angiosperms. Such gene multiplication might have led to the functional diversification of Dof proteins proceeding differently in distinct plant species.