Genome-wide identification and expression analysis of the PEBP gene family in Ziziphus jujuba var. spinosa

Phosphatidylethanolamine-binding proteins (PEBPs) are known to regulate flowering time and morphogenesis in plants. However, their identification and functions in <i>Ziziphus jujuba</i> var. <i>spinosa</i> remain uncharacterized. In this study, seven <i>ZjPEBP</i> genes were identified and were unevenly distributed across six chromosomes. Phylogenetic analysis classified them into four subfamilies: <i>FT</i>-like, <i>TFL1</i>-like, <i>MFT</i>-like, and <i>SMFT</i>-like. The <i>SMFT</i>-like subfamily likely originated from horizontal gene transfer (HGT) of prokaryotic origin, exhibiting high sequence similarity to bacteria. In contrast, the remaining six members expanded through dispersed duplication events and possess conserved structures. Cis-acting element analysis suggests that <i>ZjPEBP</i> genes may be involved in growth, development, light responsiveness, hormone signaling, and stress adaptation. Reverse transcription quantitative PCR (RT-qPCR) revealed tissue-specific expression patterns among <i>ZjPEBP</i> genes. The key flowering regulators <i>ZjFT</i> and <i>ZjTFL1</i> exhibited antagonistic expression dynamics during fruit-bearing shoot (FBS) development: <i>ZjFT</i> expression peaked when FBS reached 2-4 mm in length, coinciding with the initial stage of floral bud differentiation, whereas <i>ZjTFL1</i> maintained low expression levels throughout all developmental stages. After flowering, a clear spatiotemporal expression gradient was observed, with <i>ZjFT</i> expression in basal leaves being significantly higher than in middle and apical leaves. This expression pattern aligned with the basipetal progression of floral organ differentiation. As the basal and middle sections entered the fruit-setting stage, <i>ZjFT</i> expression was markedly downregulated. Under abscisic acid (ABA) treatment, all <i>ZjPEBP</i> genes were significantly induced, suggesting their potential involvement in both flowering regulation and ABA signaling pathways. Notably, <i>ZjSMFT</i> exhibited the most pronounced response, with expression levels upregulated approximately 400-fold at 24 hours post-treatment. This study provides a systematic characterization of the <i>ZjPEBP</i> gene family in sour jujube, laying a solid foundation for further elucidating the molecular mechanisms of flowering regulation and its potential applications in molecular breeding.