Abstract
DREB2A is an Arabidopsis transcriptional factor that binds to the DRE/CRT motif and activates the expression of target genes in response to drought and heat stresses. Although DREB2A is a stress-inducible gene, accumulation of its transcript is not sufficient for induction of downstream genes and post-translational activation of the DREB2A protein is also necessary. The DREB2A protein was supposed to be modified by ubiquitination and subjected to 26S proteasome-mediated proteolysis. Removal of a negative regulatory domain from the DREB2A protein transforms it into a constitutively stable and active form. However, it is not clear whether stabilization of DREB2A is sufficient for its activation or further activation is required.
To address this question, we treated transgenic Arabidopsis plants constitutively expressing DREB2A with the proteasome inhibiter MG132 under non-stressful condition. Although the treatment induced accumulation of the DREB2A protein, the expression of downstream genes was not induced. Therefore, transcriptional activation of target genes by DREB2A seems to require stress-specific activation of the DREB2A protein in addition to its stabilization.
