Genes for direct methylation of glycine provide high levels of glycinebetaine and abiotic-stress tolerance in Synechococcus and Arabidopsis

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 102; no. 5; pp. 1318 - 1323
• Main Authors: Waditee, R, Bhuiyan, N.H, Rai, V, Aoki, K, Tanaka, Y, Hibino, T, Suzuki, S, Takano, J, Jagendorf, A.T, Takabe, T
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 01.02.2005; National Acad Sciences
• Subjects: Arabidopsis; Arabidopsis - genetics; Arabidopsis - metabolism; Arabidopsis thaliana; Bacteria; betaine; Betaine - metabolism; Betaines; Biological Sciences; Biology; biosynthesis; Cell growth; Cyanobacterium; Cyanophyta; enzyme activity; Enzymes; flowers; Flowers & plants; gene expression; genes; Germination; glycine (amino acid); Glycine - metabolism; glycine N-methyltransferase; leaves; messenger RNA; Methylation; methyltransferases; Methyltransferases - genetics; Osmolar Concentration; Oxidation; plant response; Plant roots; Plants; Plants, Genetically Modified - metabolism; roots; Salinity; salt stress; Salt tolerance; seed productivity; stems; Stress tolerance; Synechococcus; Synechococcus - genetics; Synechococcus - metabolism; Synechococcus sp. PCC 7942; Transgenic plants
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0409017102

Betaine is an important osmoprotectant, synthesized by many plants in response to abiotic stresses. Almost all known biosynthetic pathways of betaine are two-step oxidations of choline. Recently, a biosynthetic pathway of betaine from glycine, catalyzed by two N-methyltransferase enzymes, was found. Here, the potential role of N-methyltransferase genes for betaine synthesis was examined in a freshwater cyanobacterium, Synechococcus sp. PCC 7942, and in Arabidopsis plants. It was found that the coexpression of N-methyltransferase genes in Synechococcus caused accumulation of a significant amount of betaine and conferred salt tolerance to a freshwater cyanobacterium sufficient for it to become capable of growth in seawater. Arabidopsis plants expressing N-methyltransferase genes also accumulated betaine to a high level in roots, stems, leaves, and flowers and improved seed yield under stress conditions. Betaine levels were higher than those produced by choline-oxidizing enzymes. These results demonstrate the usefulness of glycine N-methyltransferase genes for the improvement of abiotic stress tolerance in crop plants.