Characterization of the bZIP Family Transcription Factors in Astragalus membranaceus and Their Expression under Drought Stress

Astragalus membranaceus has important medicinal and ecological values, but with global changes, its growth is often negatively affected by abiotic stresses such as drought stress. The bZIP family transcription factors (TF) play important roles in plant growth and development, and the response to abiotic stresses. However, systematic identification of the bZIP gene family in A. membranaceus and their expressions under drought stress have not been reported. In the present study, genome-wide identification, chromosome localization, phylogenetic analysis, motif analysis and domain prediction of the bZIP family genes in A. membranaceus were performed. A total of 74 bZIP family members were identified in A. membranaceus, which are divided into 13 subfamilies, and members in each subfamily have similar gene structures and conserved motifs. The bZIP family members were unequally distributed on the 9 chromosomes of A. membranaceus. Four bZIP genes were generated via tandem duplication, including Am01G021190 and Am01G021150, and 45 were formed though segmental duplication. Compared with Zea mays and Oryza sativa, the bZIP genes of A. membranaceus have more collinearity with that of Medicago truncatula. The promoter analysis showed that the bZIP transcription factor family was rich in plant hormone response elements and abiotic stress response elements. The analysis of transcriptome data and qRT-PCR indicated that several bZIP TFs including AmZIP46 was involved in the response to drought stress. Further experiments showed that AmbZIP46 is only localized in the nucleus and has transcriptional activation activity. This study provided important data for understanding the biological functions of the bZIP family transcription factors in A. membranaceus.