Metabolomic and Transcriptomic Insights into Quality Formation of Orange-Red Carrot (Daucus carota L.) During Maturation

Carrots, a multi-nutrient dietary source rich in natural bioactive compounds, have gained broad recognition due to their nutritional properties and potential health-promoting effects. Studying metabolic changes during carrot maturation can provide deeper insights into the formation of their nutritional value and quality. Using Liquid Chromatograph Mass Spectrometer (LC-MS) metabolomics, we systematically profiled metabolic dynamics during orange-red carrot maturation, with large-scale compound detection, structural identification, and absolute quantification. The results showed that a total of 607 metabolites were detected. Further analysis of three distinct stages of taproot swelling and maturation revealed the following: Most sugars in primary metabolites exhibited an increasing accumulation trend across the three stages. Organic acids (including TCA cycle intermediates) displayed a pronounced decreasing accumulation pattern. Transcriptomic analysis revealed significantly upregulated expression of differentially expressed genes (DEGs) involved in the TCA cycle from the fleshy root formation stage (30 days after sowing, DAS), expansion stage (50 DAS), and maturation stage (115 DAS) in carrots. Phytochemical profiling identified 206 secondary metabolites (92 phenolic acids and 114 non-phenolic compounds). Notably, many phenolic acids maintained relatively high levels during early carrot development but exhibited a rapid decline in subsequent stages. The extensive downregulation of genes involved in phenolic acid biosynthesis pathways likely drives the rapid decline in phenolic acid content during early developmental stages. Correlation analysis further revealed significant crosstalk between primary and secondary metabolites during carrot maturation, with a pronounced negative correlation between sugars and secondary metabolites. These data provide a global perspective of carrot metabolomics and a comprehensive analysis of metabolic variations during development, establishing a molecular and metabolic basis for a deeper and more systematic understanding of carrot quality traits.