Transcriptional regulator that specifically binds to GA-rich elements (GAGA-repeats) present in regulatory sequences of genes involved in developmental processes. Homodimer. Heterodimer with BPC4. Expressed in seedlings, leaves and pistils. Detected in the base of flowers and tips of carpels, in sepal and petal vasculature, in anthers, in young rosette, in the lateral and primary roots, and in the whole ovule. Alanine-zipper domain is involved in homo- or hetero-dimerization via electrostatic interaction. Belongs to the BBR/BPC family.