We have isolated a homeobox-containing gene from Arabidopsis thaliana using a degenerate oligonucleotide probe corresponding to the most conserved region of the homeodomain. This strategy has been used previously to isolate homeobox-containing genes from Caenorhabditis, and recently from A. thaliana. The Arabidopsis genes have an unusual structure in that they have a leucine zipper motif adjacent to the carboxy terminal region of the homeo domain, a feature not found in homeobox-containing genes isolated from animals. We report the isolation and primary structure of a new member of this Arabidopsis homeobox-leucine zipper gene family. This new member has the homeodomain and leucine-zipper motif similar to the two genes previously identified, but differs from these genes in the part corresponding to the carboxy terminus of the polypeptide, as well as in size and isoelectric point of the protein.