Genome-wide analysis and expression profiling of the DREB transcription factor gene family in Malus under abiotic stress

The dehydration responsive element binding (DREB) transcription factor family is one of the most promising regulons for genetic engineering of plant responses to abiotic stresses. However, knowledge about apple DREB genes is limited. In the present study, we found, for the first time, 68 MdDREB genes that could be further classified into six subgroups against the entire genome of apple. All putative proteins from those genes contained a typical APETALA 2 domain and shared similar motifs. The predicted MdDREBs were distributed with different densities over 12 chromosomes, with five tandem duplication sites occurring simultaneously. Both Genevestigator and expressed sequence tags were used for preliminary investigations of expression patterns. Results from quantitative real-time PCR showed that transcript levels of some putative MdDREB genes were up-regulated significantly under various abiotic-stress treatments, which indicated their vital roles during stress adaptation. Identifying these genes and profiling their expression provides useful information and constitutes a foundation for their further, practical utilization in apple through gene-transfer techniques.