Genome-wide systematic characterization of <i>bZIP</i> transcription factors and their expression profiles during stem in tumorous stem mustard

The Basic Leucine Zipper (bZIP) proteins constitute a large family of transcription factors that play critical roles in plant growth regulation and the expression of resistance genes. However, to date, there have been few reports on the <i>bZIP</i> family in tumorous stem mustard (<i>Brassica juncea var. tumida</i>), an important vegetable crop. In this study, we identified 153 <i>bZIP</i> genes in tumorous stem mustard, which are unevenly distributed across 18 chromosomes and form 13 gene clusters. We systematically investigated their protein characteristics, phylogenetic relationships, gene structures, and conserved motifs. Most bZIP proteins exhibited random coil and α-helix as their predominant secondary structures. Based on RNA-Seq data from our laboratory, we analyzed the expression profiles of <i>bZIP</i> genes during the stem expansion of tumorous stem mustard. Furthermore, qRT-PCR analysis was performed to validate the expression of selected <i>bZIP</i> genes in tumorous stem mustard. The results showed that, compared with the 0 h control (25 °C untreated seedlings), five <i>BjubZIP</i> genes were significantly upregulated and eight were downregulated after 48 h of cold treatment, suggesting their potential involvement in temperature stress regulation in tumorous stem mustard. Under heat-treatment conditions, the transcription levels of <i>BjubZIP111</i> and <i>BjubZIP070</i> increased continuously over time, with expression at 48 hours significantly higher than at 12 hours. These findings provide a foundation for further functional research on <i>bZIP</i> genes in tumorous stem mustard, as well as for its breeding and production. Additionally, this study offers a theoretical basis for functional genomics research and the development of new cultivars of tumorous stem mustard.