Department of Plant, Cell and Molecular Biology, University of Tabriz, Tabriz, Iran.
Institute of Molecular Genetics and Genetic Engineering, University of Belgrade, Belgrade, Serbia.
Planta. 2024 Jul 15;260(2):53. doi: 10.1007/s00425-024-04480-5.
NH is necessary for full functionality of reduction-based Fe deficiency response in plants. Nitrogen (N) is present in soil mainly as nitrate (NO) or ammonium (NH). Although the significance of a balanced supply of NO and NH for optimal growth has been generally accepted, its importance for iron (Fe) acquisition has not been sufficiently investigated. In this work, hydroponically grown cucumber (Cucumis sativus L. cv. Maximus) plants were supplied with NO as the sole N source under -Fe conditions. Upon the appearance of chlorosis, plants were supplemented with 2 mM NHCl by roots or leaves. The NH treatment increased leaf SPAD and the HCl-extractable Fe concentration while decreased root apoplastic Fe. A concomitant increase in the root concentration of nitric oxide and activity of FRO and its abolishment by an ethylene action inhibitor, indicated activation of the components of Strategy I in NH-treated plants. Ammonium-pretreated plants showed higher utilization capacity of sparingly soluble Fe(OH) and higher root release of H, phenolics, and organic acids. The expression of the master regulator of Fe deficiency response (FIT) and its downstream genes (AHA1, FRO2, and IRT1) along with EIN3 and STOP1 was increased by NH application. Temporal analyses and the employment of a split-root system enabled us to suggest that a permanent presence of NH at concentrations lower than 2 mM is adequate to produce an unknown signal and causes a sustained upregulation of Fe deficiency-related genes, thus augmenting the Fe-acquisition machinery. The results indicate that NH appears to be a widespread and previously underappreciated component of plant reduction-based Fe deficiency response.
NH 对于植物基于还原的铁缺乏响应的完全功能是必需的。氮 (N) 主要以硝酸盐 (NO) 或铵 (NH) 的形式存在于土壤中。尽管人们普遍接受平衡供应 NO 和 NH 对最佳生长的重要性，但它们对铁 (Fe) 吸收的重要性尚未得到充分研究。在这项工作中，水培生长的黄瓜 (Cucumis sativus L. cv. Maximus) 植物在 -Fe 条件下仅以 NO 作为唯一氮源供应。当出现黄化时，通过根部或叶片向植物补充 2 mM NHCl。NH 处理增加了叶片 SPAD 和 HCl 可提取的 Fe 浓度，同时降低了根质外体 Fe。根中一氧化氮浓度和 FRO 活性的同时增加及其被乙烯作用抑制剂废除表明 NH 处理植物中策略 I 的成分被激活。用 NH 预处理的植物表现出更高的利用难溶性 Fe(OH)的能力，以及更高的根释放 H、酚类和有机酸。铁缺乏反应的主调控因子 (FIT) 及其下游基因 (AHA1、FRO2 和 IRT1) 的表达以及 EIN3 和 STOP1 的表达均通过 NH 应用增加。时间分析和分根系统的使用使我们能够提出，低于 2 mM 的 NH 浓度的持续存在足以产生未知信号，并导致铁缺乏相关基因的持续上调，从而增强铁获取机制。结果表明，NH 似乎是植物基于还原的铁缺乏响应的广泛且以前未被充分认识的组成部分。
