Genome-Wide Identification and Analysis of bZIP Family and their Expression in Response to Multiple Abiotic Stresses in Malus domestica

Basic leucine zipper proteins (bZIP), characteristically harbored a typical bZIP domain, play important roles in regulating diverse biological by acting as transcription factors. In this investigation, total 116 apple bZIP members (M.bZIP) were identified in the genome and were divided into six groups according to the phylogenetic relationship. Their chromosomal distribution and sequence similarity analysis suggested that the M.bZIP family has evolved via apple gene duplication events. By comparing the encoding sequences with the sequence in the genome, five splicing patterns of intron were found in the basic and hinge region of bZIP domain. To predict functions of M.bZIPs, analysis of protein sequences have been done. There were 24 additional conserved motifs apart from bZIP domain have been identified. Dimerization prediction suggested that almost all M.bZIPs could form hetero-dimer or homodimer or both, which helps to classify M.bZIPs into 29 distinct subfamilies. Analysis of promoter sequences of 17 randomly selected M.bZIP genes showed that M.bZIP genes may be involved in response to abiotic stresses. Their expressions were up regulated at some extent in roots and leaves under abiotic stresses. Most M.bZIP genes selected were quite sensitive to osmotic stress by qRT-PCR assay. More than half members were significantly upregulated under salt and cold stress, or by exogenous abscisic acid treatment, respectively. Our result suggested that M.bZIP family members may play important roles in plant tolerance to abiotic stress.