Genome-Wide Analysis of the bZIP Gene Family in Medicinal Wolfberry (Lycium ruthenicum): Phylogeny, Evolution and Expression Profiles

Basic leucine zipper (bZIP) transcription factors play pivotal roles in plant secondary metabolism, influencing the production of bioactive compounds that determine the medicinal value of plants. Despite their significance, a comprehensive genomic overview of bZIPs in non-model medicinal species remains limited. Here, we present the first genome-wide identification and characterization of the bZIP family in Lycium ruthenicum Murr. (black wolfberry), revealing 63 members grouped into 13 subfamilies. These genes showed conserved bZIP domains, distinct exon–intron architectures, and promoter cis-elements related to light, hormones and stress responses. Family expansion occurred through tandem (LrbZIP6-LrbZIP9 cluster) and segmental duplications under purifying selection (Ka/Ks < 1). Collinearity analysis revealed closer relationships with Solanaceae species than Arabidopsis thaliana, with LrbZIP10 and LrbZIP11 as conserved orthologs. Expression profiling identified tissue-specific patterns: LrbZIP17 showed broad expression while LrbZIP14 was fruit-specific. qRT-PCR confirmed floral-preferential (LrbZIP1, LrbZIP10, LrbZIP15, LrbZIP17, LrbZIP50) and root-specific (LrbZIP54, LrbZIP55) expression. The co-occurrence of light/hormone-responsive elements and high LrbZIP expression in anthocyanin-rich tissues suggests their regulatory roles in bioactive compound biosynthesis. This study provides foundational genomic resources for understanding L. ruthenicum bZIP evolution and identifies candidate genes for molecular breeding to enhance medicinal compound production.