GENOME-WIDE ANALYSIS OF bZIP FAMILY GENES IDENTIFIES THEIR STRUCTURAL DIVERSITY, EVOLUTIONARY PATTERNS AND EXPRESSION PROFILES IN RESPONSE TO SALT STRESS IN SUGAR BEET

Sugar beet is an important crop with significant biotechnological potential. The basic leucine zipper (bZIP) transcription factor family plays critical roles in salinity stress response in many plant species, and its investigation in sugar beet will assist in improving productivity under salt stress. Using bioinformatics software, the entire catalogue of sugar beet bZIP (BvbZIP) regular genes (45) and proteins (50) was critically examined, revealing a wide range of physicochemical properties suggesting functional versatility. Eleven phylogenetic groups were detected, based on relationships with Arabidopsis thaliana. BvbZIP genes with similar exon counts and BvbZIP proteins with similar motif compositions were typically clustered in the same phylogenetic class. Among the BvbZIP genes, similar to 94% (42) were assigned to their chromosomal locations and shown to have expanded primarily through segmental duplication. In silico gene expression analysis revealed a wide implication of BvbZIPs in the response to salinization, with 7 candidate BvbZIPs that were strongly up- or down-regulated in response to salt treatment in a salt-sensitive/tolerant cultivar, while maintaining a constant expression level in the other cultivar, implying that they play a role in sugar beet salt-responsive signalling network. We showed that these candidate genes exhibited considerable conservation with their sea beet counterparts, suggesting that they could be beneficial in enhancing sugar beet salinity tolerance. Our findings provide the first genome-wide view of the sugar beet bZIP gene family and lay the groundwork for deeper functional validation of selected candidate bZIP genes.