Genome-Wide Identification and Analysis of the WUSCHEL-Related Homeobox (WOX) Gene Family in Passion Fruit (Passiflora edulis)

The WUSCHEL-related homeobox (WOX) transcription factors (TF) regulate critical developmental processes in plants, including organ formation and stem cell maintenance. Although characterized in model species, the WOX family remains unexplored in passion fruit (Passiflora edulis). In this study, 10 WOX genes were identified in passion fruit, which are distributed across six chromosomes. We analyzed the phylogenetic relationships, gene structure, conserved motifs, and syntenic relationships of the PeWOX genes. Multiple sequence alignment analysis revealed strong conservation of the homeodomain region among WOX TF family members. Phylogenetic reconstruction further demonstrated that the 10 identified PeWOX genes in passion fruit could be classified into three distinct evolutionary clades: the WUS clade, the Intermediate clade, and the Ancient clade. The conserved motif and gene structure of WOX TF family members in the same evolutionary clade were highly consistent. Expression analysis based on RNA-seq and RT-qPCR showed that most PeWOX genes were expressed during ovule development. The expression level of PeWOX genes varies with different stress conditions. Subcellular localization analysis of tobacco leaf epidermal cells showed that PeWOX3/7/10 proteins were localized in the nucleus and cell membrane. Collectively, this study lays a foundation for future functional studies of passion fruit WOX genes.