The identification, evolutionary characterization and expression analysis of the bZIP transcription factor family in Medicago sativa

Basic leucine zipper transcription factors are one of the most extensive and conserved transcription factors in the eukaryote proteins. Currently, several bZIP transcription factors have been identified in many plants. bZIP transcription factors participate extensively in the regulation of seed storage gene expression, development, photomorphogenesis, pathogen defense, biotic and abiotic stress responses, ABA signalling, and more. In this study, 138 bZIP transcription factor-encoding genes were identified by a comprehensive computational analysis of the Medicago sativa transcriptome databases. Phylogenetic analysis of the bZIP protein sequences permits classification of the genes into 10 groups in M. sativa. The codon bias results showed that the alfalfa MsbZIP gene was biased toward the synonymous codons with A and T. Moreover, the gene ontology (GO) term annotations of the 138 MsbZIP were annotated and classified into 23 categories according to biological processes and molecular function. The co-expression relationship between MsbZIP genes showed that significant correlations existed between 372 pairs of MsbZIP genes at the 0.01 level. These results will be important for the functional characterization of bZIP transcription factors in M. sativa, and facilitate further research on the bZIP gene family regarding their evolutionary history and biological functions.