Identification of the R2R3-MYB gene family in wild jujube (Ziziphus jujuba var. spinosa) and analysis of its expression under drought stress

R2R3-MYB gene family serves as a pivotal regulatory factor in plant growth, development, and responses to environmental stresses. To investigate its function in the drought stress response of wild jujube ( Ziziphus jujuba Mill. var. spinosa ), a typical eco-economic forest species, this study performed genome-wide identification and relevant analyses of R2R3-MYB genes. A total of 91 R2R3-MYB genes (designated as ZjMYB1 to ZjMYB91 ) were identified, which were unevenly distributed across 12 chromosomes. These genes mainly encode hydrophilic and unstable proteins, 97.8% of which are localized in the nucleus. Phylogenetic analysis classified these genes into 25 clades, showing evolutionary conservation and species-specific divergence with the R2R3-MYB protein family. The expansion of the ZjMYB family is mainly characterized by segmental duplication, and all duplicated gene pairs have undergone purifying selection. ZjMYB s are widely involved in plant growth and development as well as abiotic stress responses, with the highest expression level particularly in leaf tissues; a total of 13 genes were specifically annotated as water deficit response-related genes in drought stress and abscisic acid (ABA) signaling pathways. Integrating the above analyses together with transcriptome data and qRT-PCR validation results revealed that ZjMYB5 , ZjMYB53 , ZjMYB57 and ZjMYB85 function as core drought-responsive genes, which display both tissue-specific and time-dependent expression patterns under drought stress. This study systematically elucidated the functional characteristics and regulatory network of the R2R3-MYB gene family in wild jujube, providing critical genetic resources and a theoretical basis for dissecting the molecular mechanisms underlying drought tolerance in wild jujube and breeding drought-resistant cultivars.