Institute for Multidisciplinary Applied Biology (IMAB), Dpto. Agronomía, Biotecnología y Alimentación, Universidad Publica de Navarra (UPNA), Campus Arrosadia, 31006 Pamplona, Spain.
Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, 14476 Potsdam-Golm, Germany.
J Exp Bot. 2021 Jun 22;72(13):4949-4964. doi: 10.1093/jxb/erab193.
In plants, there is a complex interaction between carbon (C) and nitrogen (N) metabolism, and its coordination is fundamental for plant growth and development. Here, we studied the influence of thioredoxin (Trx) m on C and N partitioning using tobacco plants overexpressing Trx m from the chloroplast genome. The transgenic plants showed altered metabolism of C (lower leaf starch and soluble sugar accumulation) and N (with higher amounts of amino acids and soluble protein), which pointed to an activation of N metabolism at the expense of carbohydrates. To further delineate the effect of Trx m overexpression, metabolomic and enzymatic analyses were performed on these plants. These results showed an up-regulation of the glutamine synthetase-glutamate synthase pathway; specifically tobacco plants overexpressing Trx m displayed increased activity and stability of glutamine synthetase. Moreover, higher photorespiration and nitrate accumulation were observed in these plants relative to untransformed control plants, indicating that overexpression of Trx m favors the photorespiratory N cycle rather than primary nitrate assimilation. Taken together, our results reveal the importance of Trx m as a molecular mediator of N metabolism in plant chloroplasts.
在植物中，碳（C）和氮（N）代谢之间存在着复杂的相互作用，其协调对于植物的生长和发育至关重要。在这里，我们使用过表达来自叶绿体基因组的 Trx m 的烟草植物研究了硫氧还蛋白（Trx）m 对 C 和 N 分配的影响。转基因植物表现出 C 代谢的改变（叶片中淀粉和可溶性糖积累减少）和 N 代谢的改变（氨基酸和可溶性蛋白含量增加），这表明 N 代谢的激活是以碳水化合物为代价的。为了进一步阐明 Trx m 过表达的影响，我们对这些植物进行了代谢组学和酶学分析。这些结果显示出谷氨酰胺合成酶-谷氨酸合酶途径的上调；具体来说，过表达 Trx m 的烟草植物表现出谷氨酰胺合成酶活性和稳定性的增加。此外，与未转化的对照植物相比，这些植物中观察到更高的光呼吸和硝酸盐积累，表明 Trx m 的过表达有利于光呼吸氮循环，而不是初级硝酸盐同化。总之，我们的结果揭示了 Trx m 作为植物叶绿体中 N 代谢的分子介质的重要性。
