Characterization of a novel Camellia fascicularis mutant and its metabolic regulation of flavonoid biosynthesis

Camellia fascicularis is a golden camellia species endemic to the Dawei Mountain National Nature Reserve in Yunnan Province, China. In this study, we identified a stable, heritable natural mutant of this species and systematically characterized metabolic differentiation between wild-type and mutant floral and foliar tissues by integrating morphological phenotyping, widely targeted metabolomics, physiological and biochemical quantification, and transcriptional validation of key genes. Phenotypic observation revealed that the mutant exhibited markedly enhanced petal glossiness and characteristic yellowish-green leaves. Metabolomic analysis identified 136 and 166 differentially accumulated metabolites (DAMs) in flowers and leaves, respectively; these DAMs were significantly enriched in amino acid metabolism, flavonoid biosynthesis, and ascorbate and aldarate metabolism pathways. Amino acids displayed an inverse tissue-specific accumulation pattern between flowers and leaves, suggesting a potential source-sink allocation mode. In petals, the coordinated upregulation of key flavonoid genes drove the enrichment of flavonol glycosides, which constitute the material basis for the bright coloration. In leaves, the downregulation of amino acids, together with flavonoid accumulation and reduced chlorophyll content, jointly contributed to chlorosis, while ascorbate and flavonoids synergistically enhanced antioxidant capacity. Mineral cofactors such as Fe, Zn, and Mg synergistically remodeled the whole-plant metabolic network, with concurrent increases in soluble sugar and total flavonoid contents. This study presents a novel golden camellia germplasm, reveals the regulatory mechanism underlying flavonoid biosynthesis, and proposes an integrated metabolic framework centered on amino acid source-sink allocation, providing a scientific basis for the conservation and utilization of this resource and for understanding the metabolic diversity of golden camellia.