Integrative multi-omics analyses reveal transcriptional, metabolic, and hormonal regulation of vernalization-induced flowering in Wucai (Brassica rapa).

Vernalization, a low-temperature-induced transition from vegetative to reproductive growth, is essential for flowering in many Brassica crops, including Wucai (Brassica rapa ssp. chinensis var. rosularis). To elucidate the molecular basis of vernalization in Wucai, we performed an integrative multi-omics analysis of shoot apices from cold-treated plants. Twenty-eight vernalization pathway-related genes, including homologs of FLC, FLM, VIN3, VRN, SOC1, SVP, and VIL2, exhibited conserved cold-responsive expression patterns. Transcription factors from the MYB, bHLH, bZIP, and NAC families showed dynamic regulation, implicating key members such as MYB57, bHLH3, and ABF4 in flowering control and hormonal signaling. Metabolomic profiling revealed significant enrichment of carbohydrate and amino acid metabolism, with increased levels of sucrose, glucose, galactose, glycine, serine, proline, and arginine, suggesting enhanced mobilization of energy and nitrogen during vernalization. Proline accumulation, together with upregulation of P5CS, indicates a potential role in floral transition. Hormonal analysis showed elevated auxin, kinetin, jasmonic acids, and brassinosteroids, with cold-induced BcDET2 expression correlating with increased brassinosteroid levels and early flowering. Exogenous brassinolide further promoted flowering by activating FT and SOC1 while repressing FLC. These findings provide a comprehensive molecular framework for vernalization-regulated flowering in Wucai.