A novel class of plant proteins containing a homeodomain with a closely linked leucine zipper motif.

Abstract

The homeobox, a 183 bp DNA sequence element, was originally identified as a region of sequence similarity between many Drosophila homeotic genes. The homeobox codes for a DNA‐binding motif known as the homeodomain. Homeobox genes have been found in many animal species, including sea urchins, nematodes, frogs, mice and humans. To isolate homeobox‐containing sequences from the plant Arabidopsis thaliana, a cDNA library was screened with a highly degenerate oligonucleotide corresponding to a conserved eight amino acid sequence from the helix‐3 region of the homeodomain. Using this strategy two cDNA clones sharing homeobox‐related sequences were identified. Interestingly, both of the cDNAs also contain a second element that potentially codes for a leucine zipper motif which is located immediately 3′ to the homeobox. The close proximity of these two domains suggests that the homeodomain‐leucine zipper motif could, via dimerization of the leucine zippers, recognize dyad‐symmetrical DNA sequences.