This study investigates the functional analysis of the Arabidopsis transcription factor DREB2A, which is involved in drought-responsive gene expression. DREB2A interacts with cis-acting dehydration-responsive elements/C-repeat (DRE/CRT) and is specifically induced by drought and high-salinity stresses. However, DREB2A does not activate downstream genes under normal growth conditions, suggesting that it requires posttranslational modification for activation. Domain analysis using Arabidopsis protoplasts identified a transcriptional activation domain between residues 254 and 335, and deletion of the region between residues 136 and 165 results in a constitutively active form of DREB2A. Overexpression of this constitutively active form in transgenic Arabidopsis plants significantly improved drought stress tolerance but only slightly enhanced freezing tolerance. Microarray and RNA gel blot analyses revealed that DREB2A regulates the expression of many water stress-inducible genes. Some of these genes are not downstream of DREB1A, another transcription factor that also recognizes DRE/CRT but functions in cold stress-responsive gene expression. The region between residues 136 and 165 plays a role in the stability of the DREB2A protein in the nucleus, which is crucial for its activation. The study also found that DREB2A has a negative regulatory domain in its central region, and deleting this domain results in a constitutively active form of DREB2A. Overexpression of this active form in transgenic plants activated the expression of many stress-inducible genes and improved drought stress tolerance. Additionally, the stability of the DREB2A protein is important for its activation, and the activated DREB2A regulates drought stress-responsive gene expression, enhancing drought stress tolerance in plants.This study investigates the functional analysis of the Arabidopsis transcription factor DREB2A, which is involved in drought-responsive gene expression. DREB2A interacts with cis-acting dehydration-responsive elements/C-repeat (DRE/CRT) and is specifically induced by drought and high-salinity stresses. However, DREB2A does not activate downstream genes under normal growth conditions, suggesting that it requires posttranslational modification for activation. Domain analysis using Arabidopsis protoplasts identified a transcriptional activation domain between residues 254 and 335, and deletion of the region between residues 136 and 165 results in a constitutively active form of DREB2A. Overexpression of this constitutively active form in transgenic Arabidopsis plants significantly improved drought stress tolerance but only slightly enhanced freezing tolerance. Microarray and RNA gel blot analyses revealed that DREB2A regulates the expression of many water stress-inducible genes. Some of these genes are not downstream of DREB1A, another transcription factor that also recognizes DRE/CRT but functions in cold stress-responsive gene expression. The region between residues 136 and 165 plays a role in the stability of the DREB2A protein in the nucleus, which is crucial for its activation. The study also found that DREB2A has a negative regulatory domain in its central region, and deleting this domain results in a constitutively active form of DREB2A. Overexpression of this active form in transgenic plants activated the expression of many stress-inducible genes and improved drought stress tolerance. Additionally, the stability of the DREB2A protein is important for its activation, and the activated DREB2A regulates drought stress-responsive gene expression, enhancing drought stress tolerance in plants.