Genetic engineering of glycinebetaine production toward enhancing stress tolerance in plants: Metabolic limitations
Genetic engineering of glycinebetaine production toward enhancing stress tolerance in plants: Metabolic limitations
复制标题
DOI：
10.1104/pp.122.3.747
复制
发表时间：
2000-03-01
期刊：
影响因子：
7.4
通讯作者：
Selvaraj, G
中科院分区：
文献类型：
--
作者：
Huang, J;Hirji, R;Selvaraj, G
甜菜碱（甜菜碱）在细菌、植物和动物中提供渗透保护，并在体外保护细胞成分免受恶劣条件的影响。这一发现以及其他令人信服的证据，鼓励了在缺乏甜菜碱的植物中进行甜菜碱生产工程。我们通过细菌胆碱氧化酶基因的组成表达，在拟南芥、甘蓝型油菜和烟草（Nicotiana tabacum）三种不同物种中安装了胆碱氧化代谢步骤，将胆碱这种普遍存在的物质转化为甜菜碱。独立转基因甜菜碱的最高含量分别为18.6、12.8和13 μ mol g（-1）干重，比天然甜菜碱生产者的含量低10- 20倍。然而，喂食胆碱的转基因植物合成了更多的甜菜碱。增加胆碱的添加量进一步提高了甜菜碱的合成，拟南芥的干重达到613 μ mol g(-1)，甘蓝型油菜的干重达到250 μ mol g(-1)，烟草的干重达到80 μ mol g（-1）。这些研究表明，需要加强内源性胆碱供应，以支持甜菜碱生理相关量的积累。根据相对茎部生长情况，在一些但不是全部产甜菜碱转基因品系中发现了中等的抗逆性。此外，三种植物对盐度、干旱和冰冻等胁迫的响应存在差异。
Glycinebetaine (betaine) affords osmoprotection in bacteria, plants and animals, and protects cell components against harsh conditions in vitro. This and a compelling body of other evidence have encouraged the engineering of betaine production in plants lacking it. We have installed the metabolic step for oxidation of choline, a ubiquitous substance, to betaine in three diverse species, Arabidopsis, Brassica napus, and tobacco (Nicotiana tabacum), by constitutive expression of a bacterial choline oxidase gene. The highest levels of betaine in independent transgenics were 18.6, 12.8, and 13 mu mol g(-1) dry weight, respectively, values 10- to 20-fold lower than the levels found in natural betaine producers. However, choline-fed transgenic plants synthesized substantially more betaine. increasing the choline supplementation further enhanced betaine synthesis, up to 613 mu mol g(-1) dry weight in Arabidopsis, 250 mu mol g(-1) dry weight in B. napus, and 80 mu mol g(-1) dry weight in tobacco. These studies demonstrate the need to enhance the endogenous choline supply to support accumulation of physiologically relevant amounts of betaine. A moderate stress tolerance was noted in some but not all betaine producing transgenic lines based on relative shoot growth. Furthermore, the responses to stresses such as salinity, drought, and freezing were variable among the three species.