Caputo Carla, Criado M Victoria, Roberts Irma N, Gelso M Alejandra, Barneix Atilio J
IBYF-CONICET, Universidad de Buenos Aires, Argentina.
Plant Physiol Biochem. 2009 May;47(5):335-42. doi: 10.1016/j.plaphy.2009.01.003. Epub 2009 Jan 30.
The possible regulation of amino acid remobilization via the phloem in wheat (Triticum aestivum L.) by the primary enzyme in nitrogen (N) assimilation and re-assimilation, glutamine synthetase (GS, E.C. 6.3.1.2) was studied using two conditions known to alter N phloem transport, N deficiency and cytokinins. The plants were grown for 15 days in controlled conditions with optimum N supply and then N was depleted from and/or 6-benzylaminopurine was added to the nutrient solution. Both treatments generated an induction of GS1, monitored at the level of gene expression, protein accumulation and enzyme activity, and a decrease in the exudation of amino acids to the phloem, obtained with EDTA technique, which correlated negatively. GS inhibition by metionine sulfoximide (MSX) produced an increase of amino acids exudation and the inhibitor successfully reversed the effect of N deficiency and cytokinin addition over phloem exudation. Our results point to an important physiological role for GS1 in the modulation of amino acids export levels in wheat plants.
利用氮（N）同化和再同化过程中的主要酶——谷氨酰胺合成酶（GS，E.C. 6.3.1.2），研究了在小麦（Triticum aestivum L.）中通过韧皮部进行氨基酸再转运的可能调控机制。采用已知会改变氮在韧皮部运输的两种条件，即氮缺乏和细胞分裂素处理进行研究。植株在可控条件下以最佳氮供应生长15天，然后从营养液中去除氮和/或添加6-苄基腺嘌呤。两种处理均诱导了GS1的表达，从基因表达、蛋白质积累和酶活性水平进行监测，同时通过EDTA技术发现韧皮部氨基酸渗出量减少，二者呈负相关。甲硫氨酸亚砜胺（MSX）抑制GS会导致氨基酸渗出量增加，且该抑制剂成功逆转了氮缺乏和添加细胞分裂素对韧皮部渗出的影响。我们的结果表明，GS1在调节小麦植株氨基酸输出水平方面具有重要的生理作用。
