Identification of the bZIP Gene Family and Investigation of Their Response to Drought Stress in Dendrobium catenatum

Dendrobium catenatum is a valuable Chinese herbal medicine that naturally grows on cliffs and tree trunks and is often threatened by adverse environmental conditions. The bZIP transcription factor is known to play a critical role in the response of plant to stress. However, the functions of the bZIP gene family in D. catenatum are poorly understood. In this study, 62 bZIP genes were identified from D. catenatum, which encoded proteins with an amino acid number of 130~692, a molecular weight of 15.24 to 74.94 kDa, and an isoelectric point of 5.13 to 11.58. The bZIP family can be divided into 10 subgroups by evolutionary tree analysis, and the conserved motifs of each protein subgroup were similar. The exon number of bZIP genes ranged from 1 to 12 as shown by gene structure analysis. DcbZIP promoter prediction analysis identified 21 cis-acting elements. The expression of DcbZIP genes under drought treatment was analyzed using the public RNA-seq data, and 33 upregulated genes were further screened. A co-expression network analysis revealed that 17 core genes were closely correlated with other genes and their expression was measured using RT-qPCR. The results showed that DcbZIP6, DcbZIP34, DcbZIP42 and DcbZIP47 are the main contributors to drought tolerance in D. catenatum. In summary, we identified candidate bZIP genes in D. catenatum with a apotential contribution to drought stress response, and this study lays the foundation for exploring the functions of bZIP and provides a theoretical basis for improving the drought tolerance of D. catenatum.