OsbZIP23 and OsbZIP45, members of the rice basic leucine zipper transcription factor family, are involved in drought tolerance

Many stress-inducible genes including the transcription factor basic leucine zipper (bZIP) are involved in the response of plants to environmental stresses. bZIPs are composed of two domains, a basic region for DNA binding and a leucine zipper region for dimerization. In this study, two drought-induced bZIP genes OsbZIP23 and OsbZIP45 were identified in rice. The transcription factors are orthologs of Arabidopsis bZIPs belonging to groups A and G, respectively, and are known to be involved in drought tolerance. To investigate the regulation of OsbZIP23 and OsbZIP45 expression in rice, quantitative RT-PCR was performed using RNAs from plants grown at drought stress conditions and different developmental stages. Expression of OsbZIP23 and OsbZIP45 showed positive correlation with drought tolerance. To further understand the functions of OsbZIP23 and OsbZIP45, we overexpressed OsbZIP23 and OsbZIP45 in rice using PGD1 promoter. Results of phenotypic and chlorophyll fluorescence analysis on PGD1:OsbZIP23 and PGD1:OsbZIP45 plants showed enhanced tolerance to drought stress. These results suggest that OsbZIP23 and OsbZIP45 are involved in drought stress response in rice and have a great potential for engineering drought-tolerant crops.