Molecular cloning,expressional profiling,DNA binding and trans-activation property studies of QRAP2 from Arabidopsis thaliana

Based upon analysis of data obtained from theATH1 microarrays, a cDNA that was highly induced afterdrought treatment, was isolated from Arabidopsis seedlings.RT-PCR and Quantitative Real-Time (QRT)-PCR experi-ments showed that expression level of the gene increasedsignificantly upon drought, UV, abscisic acid, high salinityand salicylic acid treatments. It was classified as a DREBsubfamily member based on multiple sequence alignmentand phylogenetic characterization. Since it encoded a proteinwith a typical ERF/AP2 DNA-binding domain and containeda glutamine-rich region near its N terminus, we named itQRAP2 (for glutamine-rich AP2). Gel retardation assay re-vealed that QRAP2 was able to form a specific complex withthe previously characterized DRE element while did notshow any affinity to the GCC box or the mutant DRE box.When fused to the GAL4 DNA-binding domain, either full-length QRAP2 or its N-terminus functioned effectively as atrans-activator in the yeast one-hybrid assay with its C-ter-minus completely inactive. Our data indicate that QRAP2could be a new member of the AP2/EREBP transcriptionfactor family involved in activation of down-stream targetgenes in response to environmental stress, especially underdrought conditions.

Based upon analysis of data obtained from the ATH1 microarrays, a eDNA that was highly induced after drought treatment, was isolated from Arabidopsis seedlings. RT-PCR and Quantitative Real-Time （QRT）-PCR experiments showed that expression level of the gene increased significantly upon drought, UV, abscisic acid, high salinity and salicylic acid treatments. It was classified as a DREB subfamily member based on multiple sequence alignment and phylogenetic characterization. Since it encoded a protein with a typical ERF/AP2 DNA-binding domain and contained a glutamine-rich region near its N terminus, we named it QRAP2 （for glutamine-rich AP2）. Gel retardation assay revealed that QRAP2 was able to form a specific complex with the previously characterized DRE element while did not show any aff＇mity to the GCC box or the mutant DRE box. When fused to the GAL4 DNA-binding domain, either fulllength QRAP2 or its N-terminus functioned effectively as a trans-activator in the yeast one-hybrid assay with its C-terminus completely inactive. Our data indicate that QRAP2 could be a new member of the AP2/EREBP transcription factor family involved in activation of down-stream target genes in response to environmental stress, especially under drought conditions.