Genome-wide identification and characterization of the MdBZR1 gene family in apple and their roles in improvement of drought tolerance

The brassinazole-resistant (BZR) transcription factors (TFs) are key components in the brassinosteroid signaling pathway that play pivotal roles in plant growth and development. However, the functions of BZR TFs in apple during stress is poorly understood. In the present study, by searching the apple genome database, we identified 11 members of the apple BZR1 gene family. We performed bioinformatic analyses on these sequences, and predicted the gene structures, protein sequences, conserved protein motifs, and cis-elements in the promotor regions. We further characterized the apple MdBZR1-6 gene by determining its subcellular location in the cell membrane and used qRT-PCR assays to examine its expression pattern in five tissues and in apple seedlings exposed to simulated drought and low-temperature stress. Our results showed that MdBZR proteins are highly conserved in plant species. In addition, we showed that the overexpression of MdBZR1-6 significantly improved the tolerance of transgenic apple callus to simulated drought stress. The results of our study establish a foundation for the further analysis of the function of MdBZR1 proteins in apple, and provide candidate genes for the potential improvement of drought tolerance in apple.