Genome-Wide Identification and Expression Analysis of the WOX Family Reveals Potential Roles in Stem Development of Euphorbia hirta

The homeobox transcription factor (TF) superfamily includes the WUSCHEL-RELATED HOMEOBOX (WOX) family, which plays a critical role in adaptive plant growth. Specifically, WOX regulates stem growth in plants, with stems serving as the structural framework for laticifers in Euphorbia hirta. However, the number of WOX gene family members in the E. hirta genome has not been reported. In this study, we identified 14 EhWOX genes in E. hirta and characterized their physicochemical properties, chromosomal locations, phylogenetic relationships, conserved motifs, gene structures, promoter cis elements, gene ontology (GO) enrichment, tissue-specific expression patterns, and subcellular localization. Chromosomal mapping indicated their distribution across nine chromosomes. Phylogenetic analysis classified these genes into three evolutionary clades. Promoter cis-element analysis identified abundant light-responsive, hormone-responsive, and stress-responsive elements. GO enrichment suggested their broad involvement in diverse biological processes. Additionally, RNA-seq revealed high expression levels of EhWOX4-6 and EhWOX14 in stems. Furthermore, RT-qPCR confirmed tissue-specific expression in stems. Moreover, experimental evidence confirmed the subcellular localization and autoactivation capability of some WOX proteins that may be involved in stem development. Overall, this study provides a comprehensive characterization of the candidate EhWOX genes and provides a foundational resource for future functional investigations into their possible roles in stem and laticifer biology.