Evolutionary and Expression Analyses of the bZIP Family in Tea Plants (Camellia sinensis) and Functional Characterization of CsbZIP3/42/6 in Response to Environmental Stresses

Basic leucine zipper (bZIP) transcription factors play crucial roles in various biological processes and responses to environmental stresses. However, the functions of the bZIP family in tea plants remain largely unexplored. Here, we identified 74 bZIP genes in tea plants (Camellia sinensis) and classified them into 12 phylogenetic groups, supported by analyses of conserved motifs and gene structures. Cis-element analysis provided insights into the potential roles of CsbZIP genes in phytohormone signaling and stress responses. Tissue-specific expression analysis demonstrated differential expression profiles of CsbZIP genes, suggesting their tissue- and stage-specific functions. Additionally, varying expression levels under different abiotic stresses indicated functional divergence of the CsbZIP family during the long-term evolution. Notably, CsbZIP3/42/6 were identified as positive regulators of drought and salt stress responses but negative regulators in response to pathogen infection, and CsbZIP42 could interact with CsbZIP3 and CsbZIP6 in regulating these environmental stresses. This study provides valuable information on potential applications for improving stress tolerance and overall plant health of tea plants.