Peinado-Torrubia Procopio, Álvarez Rosario, Lucas Marta, Franco-Navarro Juan D, Durán-Gutiérrez Francisco J, Colmenero-Flores José M, Rosales Miguel A
Plant Ion and Water Regulation Group, Instituto de Recursos Naturales y Agrobiología de Sevilla (IRNAS, CSIC), Seville, Spain.
Departamento de Biología Vegetal y Ecología, Facultad de Biología Universidad de Sevilla, Sevilla, Spain.
Front Plant Sci. 2023 Jan 10;13:1058774. doi: 10.3389/fpls.2022.1058774. eCollection 2022.
Chloride (Cl) and nitrate ( ) are closely related anions involved in plant growth. Their similar physical and chemical properties make them to interact in cellular processes like electrical balance and osmoregulation. Since both anions share transport mechanisms, Cl has been considered to antagonize uptake and accumulation in plants. However, we have recently demonstrated that Cl provided at beneficial macronutrient levels improves nitrogen (N) use efficiency (NUE). Biochemical mechanisms by which beneficial Cl nutrition improves NUE in plants are poorly understood. First, we determined that Cl nutrition at beneficial macronutrient levels did not impair the uptake efficiency, maintaining similar content in the root and in the xylem sap. Second, leaf content was significantly reduced by the treatment of 6 mM Cl in parallel with an increase in utilization and NUE. To verify whether Cl nutrition reduces leaf accumulation by inducing its assimilation, we analysed the content of N forms and the activity of different enzymes and genes involved in N metabolism. Chloride supply increased transcript accumulation and activity of most enzymes involved in assimilation into amino acids, along with a greater accumulation of organic N (mostly proteins). A reduced glycine/serine ratio and a greater ammonium accumulation pointed to a higher activity of the photorespiration pathway in leaves of Cl-treated plants. Chloride, in turn, promoted higher transcript levels of genes encoding enzymes of the photorespiration pathway. Accordingly, microscopy observations suggested strong interactions between different cellular organelles involved in photorespiration. Therefore, in this work we demonstrate for the first time that the greater utilization and NUE induced by beneficial Cl nutrition is mainly due to the stimulation of assimilation and photorespiration, possibly favouring the production of ammonia, reductants and intermediates that optimize C-N re-utilization and plant growth. This work demonstrates new Cl functions and remarks on its relevance as a potential tool to manipulate NUE in plants.
氯离子（Cl）和硝酸盐（ ）是参与植物生长的密切相关的阴离子。它们相似的物理和化学性质使它们在诸如电平衡和渗透调节等细胞过程中相互作用。由于这两种阴离子共享运输机制，Cl被认为会拮抗植物对 的吸收和积累。然而，我们最近证明，在有益的大量营养素水平下提供Cl可提高氮（N）利用效率（NUE）。有益的Cl营养提高植物NUE的生化机制尚不清楚。首先，我们确定在有益的大量营养素水平下的Cl营养不会损害 的吸收效率，根和木质部汁液中的 含量保持相似。其次，用6 mM Cl处理可显著降低叶片 含量，同时提高 的利用率和NUE。为了验证Cl营养是否通过诱导其同化作用来减少叶片 积累，我们分析了N形态的含量以及参与N代谢的不同酶和基因的活性。Cl供应增加了大多数参与将 同化为氨基酸的酶的转录积累和活性，同时有机N（主要是蛋白质）的积累也更多。甘氨酸/丝氨酸比率降低和铵积累增加表明Cl处理植物叶片中的光呼吸途径活性更高。反过来，Cl促进了光呼吸途径酶编码基因的更高转录水平。因此，显微镜观察表明参与光呼吸的不同细胞器之间存在强烈的相互作用。因此，在这项工作中，我们首次证明有益的Cl营养诱导的更高的 利用率和NUE主要是由于 同化作用和光呼吸的刺激，这可能有利于产生优化C-N再利用和植物生长的氨、还原剂和中间体。这项工作证明了Cl的新功能，并强调了其作为操纵植物NUE的潜在工具的相关性。
