Genome-wide analysis of flax bZIP genes using a T2T genome reveals abiotic stress roles

The basic leucine zipper (<i>bZIP</i>) transcription factor family plays key roles in plant growth, development, and environmental stress responses but remains poorly characterized in flax (<i>Linum usitatissimum</i> L.). We identified 99 <i>bZIP</i> genes from the telomere-to-telomere (T2T) genome and 92 from the Longya10 reference genome. These genes form 12 conserved subfamilies and contain promoter <i>cis</i>-elements related to phytohormone signaling and abiotic stress responses. Identification of 69 segmentally duplicated gene pairs indicated that large-scale duplication drove <i>bZIP</i> family expansion in flax, while miRNA-target prediction suggested Lus-miR398 as a key regulator of <i>LubZIP</i> transcription factors. Transcriptomic data showed that most <i>bZIP</i> genes were highly expressed in leaves, while RT-qPCR revealed that <i>LubZIP15</i> and <i>LubZIP45</i> (subfamilies I and H) were strongly induced by cold, drought, and salt stresses, providing a comprehensive genome-wide view of the flax <i>bZIP</i> family and their potential roles in abiotic stress tolerance.