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

## TL;DR

This study identifies and analyzes the PEBP gene family in sour jujube, revealing their roles in flowering regulation and stress response.

## Contribution

The first systematic characterization of the ZjPEBP gene family in Ziziphus jujuba var. spinosa, including their expression patterns and potential functions.

## Key findings

- Seven ZjPEBP genes were identified and classified into four subfamilies, with SMFT-like likely originating from horizontal gene transfer.
- ZjFT and ZjTFL1 show antagonistic expression during floral bud development, with ZjFT peaking at early stages.
- ZjSMFT is highly responsive to ABA treatment, with a 400-fold upregulation within 24 hours.

## Abstract

Phosphatidylethanolamine-binding proteins (PEBPs) are known to regulate flowering time and morphogenesis in plants. However, their identification and functions in Ziziphus jujuba var. spinosa remain uncharacterized. In this study, seven ZjPEBP genes were identified and were unevenly distributed across six chromosomes. Phylogenetic analysis classified them into four subfamilies: FT-like, TFL1-like, MFT-like, and SMFT-like. The SMFT-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 ZjPEBP 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 ZjPEBP genes. The key flowering regulators ZjFT and ZjTFL1 exhibited antagonistic expression dynamics during fruit-bearing shoot (FBS) development: ZjFT expression peaked when FBS reached 2–4 mm in length, coinciding with the initial stage of floral bud differentiation, whereas ZjTFL1 maintained low expression levels throughout all developmental stages. After flowering, a clear spatiotemporal expression gradient was observed, with ZjFT 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, ZjFT expression was markedly downregulated. Under abscisic acid (ABA) treatment, all ZjPEBP genes were significantly induced, suggesting their potential involvement in both flowering regulation and ABA signaling pathways. Notably, ZjSMFT 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 ZjPEBP 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.