Regulation of ascorbic acid biosynthesis and recycling during root development in carrot (Daucus carota L.).

Ascorbic acid (AsA)， also known as vitamin C， is an essential nutrient in fruits and vegetables. The fleshy root of carrot (Daucus carota L.) is a good source of AsA for humans. However， the metabolic pathways and molecular mechanisms involved in the control of AsA content during root development in carrot have not been elucidated. To gain insights into the regulation of AsA accumulation and to identify the key genes involved in the AsA metabolism， we cloned and analyzed the expression of 21 related genes during carrot root development. The results indicate that AsA accumulation in the carrot root is regulated by intricate pathways， of which the l-galactose pathway may be the major pathway for AsA biosynthesis. Transcript levels of the genes encoding l-galactose-1-phosphate phosphatase and l-galactono-1，4-lactone dehydrogenase were strongly correlated with AsA levels during root development. Data from this research may be used to assist breeding for improved nutrition， quality， and stress tolerance in carrots.