Genome-Wide Analysis of the PEBP Gene Family and Functional Characterization of BcFT-1/2 in Choy Sum (Brassica rapa subsp. chinensis var. parachinensis)

Choy Sum (Brassica rapa subsp. chinensis var. parachinensis), also known as flowering Chinese cabbage, is an important stalk vegetable in Asia. However, the unique regulatory mechanism governing its “easy-bolting yet susceptible to premature bolting” trait remains poorly understood. The phosphatidyl ethanolamine-binding protein (PEBP) family serves as a central regulator of bolting, flowering, and growth development in plants. But this gene family has not been systematically identified and studied in Choy Sum yet. Therefore, this study systematically identified and analyzed the members of the PEBP gene family in Choy Sum using bioinformatics, transcriptomics, real-time fluorescence quantification, subcellular localization, and transgenic techniques. A total of 12 BcPEBP genes were identified and categorized into three subfamilies: FT-like, TFL1-like, and MFT-like. Phylogenomic analyses revealed family expansion through whole-genome duplication with strong purifying selection. Most members have highly conserved core motifs and gene structures. Protein sequence alignment showed that BcFT-2 and BcTFL-2 underwent non-synonymous mutations at key residues. The analysis of cis-acting elements suggests that the BcPEBP gene may be influenced by complex hormone and light regulatory networks. Expression profiling demonstrated leaf-specific upregulation of BcFT-1/2 during development and shoot apices-predominant expression of BcTFL1 genes, and the expression between homologous genes of BcTFL1-1/3 is more refined. Subcellular localization confirmed dual nuclear and plasma membrane targeting of BcFT-1/2 proteins. Overexpression of BcFT-1/2 in transgenic Arabidopsis promotes flowering. These findings establish BcPEBP genes as key bolting regulators and provide molecular targets for breeding-improved varieties.