Genes for direct methylation of glycine provide high levels of glycinebetaine and abiotic-stress tolerance in Synechococcus and Arabidopsis.
Genes for direct methylation of glycine provide high levels of glycinebetaine and abiotic-stress tolerance in Synechococcus and Arabidopsis.
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DOI：
10.1073/pnas.0409017102
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发表时间：
2005-02
影响因子：
11.1
通讯作者：
Rungaroon Waditee;Md Nazmul H Bhuiyan;Vandna Rai;K. Aoki;Yoshito Tanaka;T. Hibino;Shigetoshi Suzuki;J. Takano;A. Jagendorf;T. Takabe;T. Takabe
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文献类型：
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作者：
Rungaroon Waditee;Md Nazmul H Bhuiyan;Vandna Rai;K. Aoki;Yoshito Tanaka;T. Hibino;Shigetoshi Suzuki;J. Takano;A. Jagendorf;T. Takabe;T. Takabe
甜菜碱是一种重要的渗透保护剂，由许多植物合成以应对非生物胁迫。几乎所有已知的甜菜碱的生物合成途径都是胆碱的两步氧化。近年来，在淡水蓝藻Synechococcus sp. PCC 7942和拟南芥中发现了由两种N-甲基转移酶催化甘氨酸合成甜菜碱的途径，研究了N-甲基转移酶基因在甜菜碱合成中的潜在作用。结果发现，N-甲基转移酶基因在聚球藻的共表达引起积累了显着量的甜菜碱，并赋予耐盐淡水蓝藻足以使它成为能够在海水中生长。表达N-甲基转移酶基因的拟南芥植物在根、茎、叶和花中也积累了高水平的甜菜碱，并在胁迫条件下提高了种子产量。甜菜碱水平高于胆碱氧化酶产生的水平。这些结果证明了甘氨酸N-甲基转移酶基因对于提高作物的非生物胁迫耐受性的有用性。
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.