Analysis of rabbiteye blueberry metabolomes and transcriptomes reveals mechanisms underlying potassium-induced anthocyanin production

Environmental factors play an important role in anthocyanin biosynthesis, and potassium, an essential nutrient for blueberry growth, can act as an enzyme activator. However, few reports exist on the transcriptional and anthocyanin metabolic changes in blueberries regulated by potassium. In this study, blueberries treated with potassium at different stages were compared for changes in enzyme activity, transcription, and metabolism related to anthocyanin synthesis. The results showed that potassium treatment significantly enhanced the activities of key enzymes F3H, F3'5'H, and UFGT in the anthocyanin synthesis pathway of blueberry fruit. Metabolomic results indicated that the contents of malvidin, petunidin, and delphinidin were higher with potassium fertilization, and potassium treatment promoted the early color change of blueberry fruit. The transcriptome analysis identified 102 glucose metabolism-related genes and 12 differential potassium transport genes potentially involved in potassium-regulated anthocyanin synthesis and accumulation. It was found that thirteen genes relate to anthocyanin synthesis. UFGT, F3H, CHI, HCT, C12RT1, DFR, and F3'5'H were all closely associated with potassium-controlled flavonoid and anthocyanin metabolite synthesis. It provides valuable insights into the molecular mechanisms that regulate the synthesis of anthocyanins in blueberries. Analytically pure potassium sulfate was dissolved in water, and 10g of potassium fertilizer was applied to each plant at the flowering stage (KH) and young fruit stage (YG), respectively. The same amount of water was applied for the CK treatment.