Tetrahydrofolate biosynthesis and distribution in higher plants.

One-carbon transfer reactions are mediated by H4F (tetrahydrofolate), a soluble coenzyme (vitamin B9) that is synthesized de novo by plants and microorganisms, and absorbed from the diet by animals. H4F synthesis in plants is quartered between the plastids, the cytosol and the mitochondria, a spatial distribution that is not observed in the other organisms and that suggests a complex intracellular traffic. Also, the activity of H4F synthesis fluctuates during plant growth, depending on the tissue and the developmental stage of the seedling, thus illustrating the flexibility of one-carbon metabolism in these organisms. This paper will focus on our recent knowledge about H4F synthesis in the plant cell and will briefly describe the activity of the pathway during the growth and development of the seedling.