Integrated Multi-Omics Analysis Elucidates the Anthocyanin Regulatory Mechanism Underlying Flower Color Variation in Impatiens walleriana

Impatiens walleriana is a widely cultivated ornamental species extensively used in landscaping and garden design, with its vibrant floral colors constituting one of the primary determinants of its ornamental value. We found in preliminary observations that treatment of I. walleriana seeds with colchicine at 60 mg L−1 induced significant flower color variation, with petals changing from purple to pink. Based on this, the present study used the wild-type (purple) and induced mutant plants (pink) of I. walleriana as materials, and systematically elucidated the molecular regulatory mechanism underlying its flower color variation via integrated analysis of targeted metabolomics and transcriptomics. Metabolomic analysis identified 84 anthocyanin-related metabolites. Metabolite composition and accumulation levels differed significantly between Iw-MU and Iw-WT. Pelargonidin, peonidin, and petunidin were markedly elevated in Iw-MU, while procyanidins accumulated to higher levels in Iw-WT. These metabolic differences may serve as the key metabolic basis for the petal color transition to pink. Transcriptomic analysis identified a total of 689 differentially expressed genes, of which 386 were upregulated and 303 were downregulated. Subsequent functional annotation and enrichment analysis revealed that the flavonoid biosynthesis pathway played a key regulatory role in flower color variation. Among these, the significant downregulation of key anthocyanin biosynthetic genes, DFR and ANS, likely suppressed the production of colored anthocyanins. In contrast, the expression levels of ANR and LAR genes were significantly upregulated, which may drive the metabolic flux to shift toward proanthocyanidin biosynthesis. This study elucidated the metabolomic composition characteristics and key regulatory genes associated with the floral color transition from pinkish-purple to light pink in I. walleriana, as well as clarified the core metabolic pathways and molecular regulatory mechanisms underlying this variation. These findings provide a theoretical foundation for the genetic improvement of flower color and the breeding of new cultivars in I. walleriana.