State Key Laboratory of Conservation and Utilization of Subtropical Agro-Bioresources, Guangdong Laboratory for Lingnan Modern Agriculture, College of Forestry and Landscape Architecture, South China Agricultural University, Guangzhou 510642, China.
Boone Pickens School of Geology, Oklahoma State University, Stillwater, OK 74074, United States.
Microbiol Res. 2024 Dec;289:127906. doi: 10.1016/j.micres.2024.127906. Epub 2024 Sep 20.
The challenge of soil salinization and alkalization, with its significant impact on crop productivity, has raised growing concerns with global population growth and enhanced environmental degradation. Although arbuscular mycorrhizal fungi (AMF) and calcium ions (Ca) are known to enhance plant resistance to stress, their combined effects on perennial ryegrass' tolerance to salt and alkali stress and the underlying mechanisms remain poorly understood. This study aimed to elucidate the roles of Arbuscular mycorrhizal (AM) fungus Rhizophagus irregularis and exogenous Ca application in molecular and physiological responses to salt-alkali stress. AM symbiosis and exogenous Ca application enhanced antioxidant enzyme activity and non-enzymatic components, promoting reactive oxygen species (ROS) scavenging and reducing lipid peroxidation while alleviating oxidative damage induced by salt-alkali stress. Furthermore, they enhanced osmotic balance by increasing soluble sugar content (Proportion of contribution of the osmotic adjustment were 34∼38 % in shoots and 30∼37 % in roots) under salt stress and organic acid content (Proportion of contribution of the osmotic adjustment were 32∼36 % in shoots and 37∼42 % in roots) under alkali stress. Changes in organic solute and inorganic cation-anion contents contributed to ion balance, while hormonal regulation played a role in these protective mechanisms. Moreover, the protective mechanisms involved activation of Ca-mediated signaling pathways, regulation of salt-alkali stress-related genes (including LpNHX1 and LpSOS1), increased ATPase activity, elevated ATP levels, enhanced Na extrusion, improved K absorption capacity, and a reduced Na/K ratio, all contributing to the protection of photosynthetic pigments and the enhancement of photosynthetic efficiency. Ultimately, the combined application of exogenous Ca and AMF synergistically alleviated the inhibitory effects of salt-alkali stress on perennial ryegrass growth. This finding suggested that exogenous Ca may participate in the colonization of perennial ryegrass plants by R. irregularis, while AM symbiosis may activate Ca pathways. Consequently, the combined treatment of AM and Ca is beneficial for enhancing plant regulatory mechanisms and increasing crop yield under salt-alkali stress.
土壤盐渍化和碱化的挑战，由于其对作物生产力的重大影响，随着全球人口增长和环境恶化而引起了越来越多的关注。虽然丛枝菌根真菌（AMF）和钙离子（Ca）已知可以增强植物对胁迫的抗性，但它们对多年生黑麦草对盐和碱胁迫的耐受性的综合影响及其潜在机制仍知之甚少。本研究旨在阐明丛枝菌根（AM）真菌根内球囊霉（Rhizophagus irregularis）和外源 Ca 处理在分子和生理上对盐-碱胁迫的响应。AM 共生和外源 Ca 处理增强了抗氧化酶活性和非酶成分，促进了活性氧（ROS）的清除，降低了脂质过氧化作用，减轻了盐-碱胁迫引起的氧化损伤。此外，它们通过增加盐胁迫下的可溶性糖含量（渗透调节的贡献率为 34∼38%在地上部分和 30∼37%在根部）和碱胁迫下的有机酸含量（渗透调节的贡献率为 32∼36%在地上部分和 37∼42%在根部）来增强渗透平衡。有机溶质和无机阴阳离子含量的变化有助于离子平衡，而激素调节在这些保护机制中发挥作用。此外，保护机制涉及 Ca 介导的信号通路的激活、盐-碱胁迫相关基因（包括 LpNHX1 和 LpSOS1）的调节、ATP 酶活性的增加、ATP 水平的提高、Na 外排的增强、K 吸收能力的提高和 Na/K 比的降低，所有这些都有助于保护光合色素和提高光合效率。最终，外源 Ca 和 AMF 的联合应用协同缓解了盐-碱胁迫对多年生黑麦草生长的抑制作用。这一发现表明，外源 Ca 可能参与了 R. irregularis 对多年生黑麦草植物的定殖，而 AM 共生可能激活了 Ca 途径。因此，AM 和 Ca 的联合处理有利于增强植物的调节机制，并在盐-碱胁迫下提高作物产量。
