Ascorbate Biosynthesis in Arabidopsis Cell Suspension Culture

The biosynthesis of l-ascorbic acid (l-AA) in an Arabidopsis (L.) Heynh. cell suspension culture was studied by quantifying the effects of incubation with a range of potential biosynthetic precursors, analogs, and inhibitors on the intracellular levels of reduced and oxidized forms of l-AA. Our results support the recently published biosynthetic pathway of l-AA from l-galactose (G.L. Wheeler, M.A. Jones, N. Smirnoff [1998] Nature 393: 365–369), but suggest that Arabidopsis cell suspension culture simultaneously contains two other routes leading to l-AA. The possible physiological significance of these alternate routes is discussed.