Abstract
3-Phosphoglycerate, an intermediate of Calvin-Benson cycle, glycolysis, and pentose phosphate pathway, is converted to serine by 3-phosphoglycerate dehydrogenase and two consecutive reactions. Betaine is an important osmoprotectant, and synthesized by many plants in response to abiotic stresses. Almost all known biosynthetic pathways of betaine are two-step oxidations of choline, recently a novel biosynthetic pathway of betaine from glycine, catalyzed by two N-methyltransferase enzymes, was found in a halotolerant cyanobacterium Aphanothece halophytica. Recent studies suggest that for the accumulation of large amount of betaine, supply of precursors such as ethanolamine, serine, and glycine are important. Here, the potential role of PGDH for betaine synthesis was examined in 1) Aphanothece halophytica and 2) in /Arabidopsis plants which were transformed with two N-methyltransferase genes. Their results will be presented.
