Abstract
Under abiotic stress conditions such as drought and high salinity, ABA levels increase in plants, and ABA regulates the expression of many genes that function in plant stress tolerance. A conserved cis-element designated ABRE (ABA-responsive element), which controls ABA-responsive gene expression, has been identified in promoter regions of ABA-regulated genes. Arabidopsis cDNAs encoding bZIP-type transcription factors referred as ABRE-binding (AREB) proteins were isolated using the yeast one-hybrid screening method. Among these transcription factors, expression of AREB1, AREB2, and ABF3 was upregulated by ABA, dehydration, and high-salinity stresses in Arabidopsis plants. Overexpression of the intact AREB1 is insufficient to lead to expression of downstream genes. Post-transcriptional activation of AREB1 by phosphorylation was necessary for its maximum activation. Using in gel kinase assay, we are analyzing phosphorylation of AREB1 peptide fragments under drought and high-salt stress conditions.
