Department of Crop Science, University of Guelph, N1G 2W1, Guelph, Ontario, Canada.
Plant Cell Rep. 1990 Jul;9(2):80-3. doi: 10.1007/BF00231554.
Phosphinothricin is a non-selective herbicide which inhibits glutamine synthetase (EC 6.3.1.2) activity causing an overaccumulation of ammonia in higher plants. Alfalfa (Medicago sativa L) shoot tissue and petiole-derived callus exposed to phosphinothricin show 50 and 70% reductions, respectively, in glutamine synthetase activity with a concomitant rise of 10 and 20 fold, respectively, in endogenous ammonia. The diffusibility of ammonia may limit the use of a detoxifying gene, phosphinothricin acetyltransferase, as a selectable marker for alfalfa transformation. However, the addition of up to 40 times the standard levels of ammonium nitrate to the culture media used in this study had no effect on callus growth, although glutamine synthetase activity was inhibited by 50% and endogenous ammonia increased 27 fold. Therefore, ammonia accumulation may not be the primary cause of cell death in alfalfa after exposure to phosphinothricin. It follows that diffusion of ammonia from cell to cell would not restrict the selection for phosphinothricin acetyltransferase transformed cells, thereby indicating that this enzyme could be used as a selectable marker in transformation experiments.
膦丝菌素是一种非选择性除草剂，它抑制谷氨酰胺合成酶（EC 6.3.1.2）的活性，导致高等植物中氨的过度积累。暴露于膦丝菌素的紫花苜蓿（Medicago sativa L）芽组织和叶柄衍生愈伤组织中的谷氨酰胺合成酶活性分别降低 50%和 70%，同时内源氨分别增加 10 倍和 20 倍。氨的扩散性可能限制了解毒基因，膦丝菌素乙酰转移酶作为紫花苜蓿转化的选择标记的使用。然而，在本研究中使用的培养基中添加高达标准水平 40 倍的硝酸铵对愈伤组织生长没有影响，尽管谷氨酰胺合成酶活性抑制了 50%，内源氨增加了 27 倍。因此，氨积累可能不是紫花苜蓿暴露于膦丝菌素后细胞死亡的主要原因。由此可以推断，氨从一个细胞扩散到另一个细胞不会限制对膦丝菌素乙酰转移酶转化细胞的选择，从而表明该酶可以在转化实验中用作选择标记。
