Genome‑wide Identification and Characterization of Transcription Factors of Basic Leucine Zipper Family in Malus domestica
Basic leucine zipper proteins (bZIP) contain a basic DNA-binding region and a leucine zipper region, acting as transcriptional factors in regulation of gene expression exclusively in eukaryotes. In this investigation, total 116 bZIP members were identified in apple genome and mapped on all 17 chromosomes with various densities as M.bZIPs. All these members were divided into six groups according to the phylogenetic relationship combining with bZIPs from rice and Arabidopsis. Investigating gene structure of M.bZIPs, five splicing patterns of intron were found in the DNA-binging region with no splicing position and splicing positions at different nucleotide of codons or different positions. Analyzing of protein structure of M.bZIPs, twenty-five motifs were identified with certain characteristic in different phylogenetic groups. To predict dimerization of leucine zipper region, the key positions of amino acid in heptad(s) were investigated. The results showed that most M.bZIPs may form hetero-dimer or homo-dimer and some M.bZIPs may form both. Expression experiment revealed that M.bZIP genes have organ-specific expression and widely expressed in flowers, leaves, and fruits. To investigate the response of M.bZIPs to abiotic stresses, the promoter sequences of randomly selected M.bZIP genes were analyzed. Cis-acting elements related to multiple stresses were found existing widely in promoter sequences. Quantitative real-time PCR results further demonstrated that the expression of some M.bZIP genes were quite sensitive to exogenous abscisic acid and osmotic treatments.