Widely Targeted Metabolomics Analyses Clarify the Biosynthetic Pathways Responsible for Flavonoids in Sweet Potato (Ipomoea batatas (L.) Lam.) Storage Roots

Sweet potatoes (Ipomoea batatas (L.) Lam.) are a widely cultivated member of the Convolvulaceae family. Despite intensive agricultural interest, the metabolic determinants of sweet potato quality remain poorly understood owing to a lack of reliable or systematic sweet potato metabolite analyses. This study aimed to reveal the mechanism of flavonoid biosynthesis using widely targeted metabolomics and qRT-PCR analysis of white (S19) and yellow (BS) sweet potatoes. We found that the PAL, C4H, 4CL, CHS, CHI, IFS, F3H, F3'H, DFR, ANS, and ANR genes were differentially expressed in BS. Upregulation of PAL, C4H, 4CL, and CHS led to the accumulation of large amounts of chalcone, which is highly expressed in yellow flesh, resulting in the yellow color of BS. In S19, the high expression of FLS and the low expression of DFR inhibited pigment accumulation, while the low expression of CHS also inhibited flavonoid synthesis, ultimately leading to the white color. In conclusion, this study identified the main differentially expressed genes and their metabolites in the flavonoid biosynthesis pathway, and preliminarily elucidated the mechanism underlying the different flesh colors in sweet potato, thus providing new insights into the composition and abundance of metabolites in sweet potatoes with different-colored flesh.