Characterization of AtbZIP2, AtbZIP11 and AtbZIP53 from the group S basic region-leucine zipper family in Arabidopsis thaliana

We have previously described the lip19 subfamily of basic region-leucine zipper protein (bZIP)-encoding genes from plants. Phylogenetic analysis of bZIP-encoded genes of Arabidopsis thaliana revealed that AtbZIP53 belongs to the lip19 subfamily and that four other members, AtbZIP1, AtbZIP2, AtbZIP11 and AtbZIP44 have close relationships to this subfamily. Here, we further characterized AtbZIP53 and two additional bZIP genes, AtbZIP2 and AtbZIP11. All three gene products are localized to the nucleus and show strong DNA binding activity to hexamer and C/G box hybrid sequences. Transactivation activities of the proteins were examined in plant cells. The expression of the genes upon exposure to various abiotic stresses and to hormone treatments was examined in Arabidopsis. We found that AtbZIP11 and AtbZIP53 were responsive to cytokinin and high salt stress, respectively. Based on these data, the physiological roles are discussed.