Characterization of bZIP transcription factors from Dimocarpus longan Lour. and analysis of their tissue-specific expression patterns and response to heat stress

Members of the bZIP transcription factor family play crucial roles in the regulation of plant development, biosynthesis of secondary metabolites, and response to abiotic and biotic stresses. To date, multiple bZIPs have been identified and investigated in numerous plant species. However, few studies have characterized bZIPs from Dimocarpus longan Lour. In this study, nine bZIPs from D. longan were identified from RNA-Seq data and further verified using the NCBI conserved domain search tool and Pfam database. Bioinformatics tools were used to systematically analyse the physicochemical properties, protein structures, multiple sequence alignment, motif compositions, evolutionary relationships, secondary structures, subcellular localization, phosphorylation sites, signal peptides, GO annotations and protein–protein interactions of the DlbZIPs. The expression patterns of the nine DlbZIPs were evaluated by qRT-PCR in roots and leaves and in response to varying durations of a 38°C heat treatment. DlbZIP3, DlbZIP5, DlbZIP6 and DlbZIP7 were differentially expressed between root and leaf tissues. All nine DlbZIPs responded to heat treatment in both roots and leaves, but their specific expression levels differed. DlbZIP4 and DlbZIP8 were highly expressed in roots after heat treatment, whereas DlbZIP1 and DlbZIP5 were highly expressed in leaves after heat treatment. These findings lay a foundation for increasing active secondary metabolite content and improving abiotic stress tolerance in D. longan using transgenic technology.