Abstract
Vitamin C (ascorbate) is a potent water-soluble antioxidant and acts as a cofactor for many enzymes. Plants contain ascorbate at very high levels, and, for humans, they are the main dietary source of this vitamin. Despite the tremendous efforts made so far, the following fundamental questions still remain: why and how plants accumulate ascorbate in their body. During the evolution of plants, they have acquired original pathways for ascorbate biosynthesis as well as the use of ascorbate for the antioxidant system and recycling. These allowed plants to synthesize ascorbate ‘safely’ and to use it for the antioxidant system very efficiently. Recently, our research group has studied 1) the impacts of ascorbate levels on plant growth and stress resistance, 2) the physiological significance of plant-specific H2O2-scavenging enzymes (ascorbate peroxidases), and 3) the molecular mechanism of ascorbate recycling and its role in ascorbate pool size regulation. In this review, I summarize recent advances in this field and try to answer the above two fundamental questions.
