Integrated transcriptomic and metabolomic analyses revealed paclobutrazol-mediated regulation of flower bud differentiation in Camellia japonica ‘High Fragrance’

Flower bud differentiation is regulated by complex physiological and molecular networks. Paclobutrazol (PBZ) has been reported to induce early flowering in Camellia species, but the underlying mechanisms remain unclear. In this study, we combined transcriptomic and metabolomic analyses to investigate PBZ-induced flowering in Camellia japonica 'High Fragrance. Transcriptome analysis identified differentially expressed genes (DEGs) enriched in plant hormone signal transduction and starch and sucrose metabolism pathways, while metabolome analysis revealed that differentially accumulated metabolites were significantly enriched in riboflavin metabolism, thiamine metabolism, taurine and hypotaurine metabolism, and arginine biosynthesis. Correlation analysis of flowering-related DEGs revealed that COL4 , COL10 , and COL16 acted as hub genes and, together with COP1 and S OC1 , were significantly positively correlated with a subset of genes in multiple hormone signaling pathways (cor > 0.85, p < 0.05). Furthermore, weighted gene co-expression network analysis (WGCNA) identified hub genes related to hormone signaling and carbohydrate metabolism, such as G3PA , PSB28 , PIP21 , and BLH9 , highlighting potential key regulators of PBZ-induced flowering. Collectively, these results provide novel insights into the molecular and metabolic mechanisms by which PBZ promotes early flowering in the ‘High Fragrance’ cultivar, offering guidance for breeding early-flowering aromatic C. japonica cultivars. • PBZ treatment promotes early flowering in Camellia japonica 'High Fragrance' • PBZ reshapes hormone signaling and starch–sucrose metabolism during floral bud development • Key flowering regulators coordinate with auxin, zeatin and ABA signaling • WGCNA identifies hub genes involved in photosynthesis and carbohydrate metabolism • PBZ inhibits photosynthesis and reallocates resources toward reproduction