Adavi Sandeep B, Sathee Lekshmy, Pandey Rakesh, Yadav Prachi
Division of Plant Physiology, ICAR-Indian Agricultural Research Institute, New Delhi, 110012, India; National Institute of Biotic Stress Management, Baronda, Raipur, (C.G), 493225, India.
Division of Plant Physiology, ICAR-Indian Agricultural Research Institute, New Delhi, 110012, India.
Nitric Oxide. 2025 Aug 20;159:11-22. doi: 10.1016/j.niox.2025.08.003.
Nitrate (NO), besides serving as a major N source, also acts as a signalling molecule in plant growth and development. Studies on NO dependent regulation of root growth in wheat (Triticum aestivum) are mostly limited to morphophysiological changes, while the underlying signalling mechanisms remain largely unexplored. To bridge this gap, the present study aims to get a mechanistic understanding of the NO dependent regulation of root growth in wheat seedlings. For this, uniformly germinated two days old wheat seedlings were exposed to nitric oxide (NO) donor sodium nitroprusside (SNP), auxin source Indole-3-butyric acid (IBA), calcium chloride as source of calcium (Ca), NO scavenger 2-4-carboxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO), polar auxin transport inhibitor 2,3,5-triiodobenzoic acid (TIBA) and calcium chelator ethylene glycol-bis (β-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) with NO as a major determinant. After seven days, root traits were analyzed, and a tissue localization assay was performed using Fluo-3 AM, DAF-FM, and salkowski reagents to visualize the distribution of Ca, NO, and indole-3-acetic acid (IAA) in root tissues, respectively. The study reveals that the cross-talk of nitric oxide (NO), auxin and calcium (Ca) modulates NO regulated root growth in wheat seedlings. The changes in cytosolic Ca concentration ([Ca]) are a major mediator in the regulation of root growth. High NO (5 mM) in combination with exogenous IBA and Ca suppresses the root growth, with ethylene acting downstream of [Ca]. We observed a synergistic effect between NO and endogenous IAA (Indole-3-acetic acid) in lateral root (LR) growth. In LRs, the external NO enhances the NO production, which is further augmented by the elevated [Ca] levels. Our results indicate that endogenous IAA plays a pivotal role in regulating root hair development on LR with NO and [Ca] functioning downstream of the signalling cascade. However, the high NO was found to counteract the root hair formation by importing the shoot-derived auxin. These findings provide valuable insights into the intricate signalling interactions between nitric oxide, auxin, and calcium in NO regulated root development in wheat, with potential targets for enhancing nutrient uptake efficiency. Further work is necessary to identify downstream signalling components and examine how shoot-to-root signalling modulates the root architectures under different NO regimes.
硝酸盐（NO）除了作为主要的氮源外，还在植物生长发育中充当信号分子。关于小麦（Triticum aestivum）中NO依赖的根系生长调控的研究大多局限于形态生理变化，而潜在的信号传导机制在很大程度上仍未被探索。为了弥补这一差距，本研究旨在深入了解小麦幼苗中NO依赖的根系生长调控机制。为此，将均匀萌发两天的小麦幼苗暴露于一氧化氮（NO）供体硝普钠（SNP）、生长素源吲哚 - 3 - 丁酸（IBA）、钙源氯化钙（Ca）、NO清除剂2 - （4 - 羧基苯基） - 4,4,5,5 - 四甲基咪唑啉 - 1 - 氧基 - 3 - 氧化物（cPTIO）、极性生长素运输抑制剂2,3,5 - 三碘苯甲酸（TIBA）和钙螯合剂乙二醇 - 双（β - 氨基乙基醚） - N,N,N',N' - 四乙酸（EGTA）中，其中NO是主要决定因素。七天后，分析根系性状，并使用Fluo - 3 AM、DAF - FM和索尔科夫斯基试剂进行组织定位分析，以分别观察Ca、NO和吲哚 - 3 - 乙酸（IAA）在根组织中的分布。研究表明，一氧化氮（NO）、生长素和钙（Ca）之间的相互作用调节了小麦幼苗中NO调控的根系生长。细胞质钙浓度（[Ca]）的变化是根系生长调控的主要介导因素。高浓度NO（5 mM）与外源IBA和Ca共同作用会抑制根系生长，乙烯在[Ca]的下游起作用。我们观察到NO与内源IAA（吲哚 - 3 - 乙酸）在侧根（LR）生长中具有协同效应。在侧根中，外源NO会增强NO的产生，而[Ca]水平的升高会进一步增强这种作用。我们的结果表明，内源IAA在调节侧根上的根毛发育中起关键作用，NO和[Ca]在信号级联的下游发挥作用。然而，高浓度NO被发现通过导入茎源生长素来抵消根毛的形成。这些发现为小麦中NO调控的根系发育过程中一氧化氮、生长素和钙之间复杂的信号相互作用提供了有价值的见解，为提高养分吸收效率提供了潜在靶点。有必要进一步开展工作，以确定下游信号成分，并研究在不同NO水平下，地上部到根部的信号传导如何调节根系结构。
