CHARACTERIZATION OF A DRE-BINDING TRANSCRIPTION FACTOR FROM ASPARAGUS (ASPARAGUS OFFICINALIS L.) AND ITS OVEREXPRESSION IN ARABIDOPSIS RESULTING IN SALT- AND DROUGHT-RESISTANT TRANSGENIC PLANTS

A new full-length cDNA encoding an AP2/EREBP domain-containing transcription factor named AoDREB was isolated from Asparagus officinalis L. using the RACE-PCR method. It is a homolog to the dehydration-responsive element binding protein (DREB) and classified to the A6 subgroup of the DREB subfamily. Using the yeast one-hybrid system, we conducted a DRE binding assay and demonstrated that AoDREB can bind the DRE element specifically. A transcriptional activity assay showed that AoDREB is a transcription factor capable of activating expression of the reporter gene in yeast. RT-PCR analysis revealed that expression of the AoDREB gene is induced under 20% PEG and high salinity stress, whereas no obvious response to low temperature was observed. Overexpression of AoDREB in transgenic Arabidopsis caused no growth retardation and induced stronger expression of the target genes, including RD29A and COR15A, than in wild type, resulting in increased tolerance of transgenic Arabidopsis to drought and high salinity. These results suggest that introduction of an exogenous AoDREB into plants is an effective way to improve plant drought and salinity tolerance.