A NEW HOMEODOMAIN-LEUCINE ZIPPER GENE FROM ARABIDOPSIS-THALIANA INDUCED BY WATER-STRESS AND ABSCISIC-ACID TREATMENT

We report the isolation and characterization of a new homeobox gene fr om Arabidopsis thaliana using a polymerase chain reaction (PCR) clonin g strategy. The full-length cDNA, designated Athb-12, encodes a protei n of 235 amino acids. It contains the conserved DNA binding domain and the leucine zipper motif, characteristic of the homeodomain-leucine z ipper family of transcription factors. The deduced amino acid sequence of Athb-12 shows over 80% identity to the Arabidopsis Athb-7 in the h omeodomain (82%) and the leucine zipper motif (80%) of the proteins. H owever, outside the homeodomain and the leucine zipper motif, the homo logy is significantly lower. RNA analysis identified only one 0.96 kb transcript consistent with the size of Athb-12 cDNA. The Athb-12 trans cript was detected in stem, leaf, flower and root as well as in seedli ngs. Treatment with water stress and exogenous abscisic acid (ABA) res ulted in the accumulation of Athb-12 mRNA, similar to that of Athb-7. However, the time course of the Athb-12 response to ABA differed from that of Athb-7, suggesting that both genes, in response to ABA, are re gulated in different manners. Taken together, these data suggest that Athb-12 and Athb-7 are members of a related gene family involved in th e plant's response to water stress.