Systematic characterization of the bZIP transcription factor family of Japanese plum (Prunus salicina Lindl.) and their potential role in phenolic compound biosynthesis

• This is the first systematic study of the bZIP gene family in Prunus salicina Lindl. It has identified 60 genes distributed across 12 functional groups. • Through RNA-seq analysis of developing fruits, we identified 53 actively expressed bZIP genes. • We detected 29 significant correlations between expressed genes and phenolic compounds. • Here, a key area of horticultural science is addressed by linking transcriptional regulation to fruit nutritional content. The basic leucine zipper (bZIP) transcription factors are essential in several plant developmental and physiological processes. The gene family encoding these proteins has yet to be studied in Japanese plum ( Prunus salicina Lindl.), a species characterized by a high phenolic content in their fruits. In this work, we analyzed the Prunus salicina reference genome, identifying 60 genes coding for bZIP proteins. According to the predicted amino acid sequences, the PsabZIPs were distributed in 12 groups. We also studied the distribution and duplication events of these bZIP genes in the 'Sanyueli' reference genome. Their orthologues were analyzed in three additional Prunus species, with peach ( Prunus persica (L.) Batsch) identified as the species containing the highest number of bZIP-coding genes. An RNA-seq analysis of fruits at different developmental stages in two Japanese plum cultivars allowed us to detect 53 expressed bZIP-coding genes, suggesting a role in fruit development. Through a correlation analysis between their expression and nine phenolic compounds, we detected 29 genes with a significant association (p-value <0.001) with the biosynthesis of these compounds. These results suggest the potential role of bZIP transcription factors as regulators of phenolic compound biosynthesis in Japanese plum.