Molecular mechanisms of plant adaptive responses to heavy metals stress

Abstract

Heavy metals (HMs) are among the main environmental pollutants that can enter the soil, water bodies, and the atmosphere as a result of natural processes (weathering of rocks, volcanic activity), and also as a result of human activities (mining, metallurgical and chemical industries, transport, application of mineral fertilizers). Plants counteract the HMs stresses through morphological and physiological adaptations, which are imparted through well‐coordinated molecular mechanisms. New approaches, which include transcriptomics, genomics, proteomics, and metabolomics analyses, have opened the paths to understand such complex networks. This review sheds light on molecular mechanisms included in plant adaptive and defense responses during metal stress. It is focused on the entry of HMs into plants, its transport and accumulation, effects on the main physiological processes, gene expressions included in plant adaptive and defense responses during HM stress. Analysis of new data allowed the authors to conclude that the most important mechanism of HM tolerance is extracellular and intracellular HM sequestration. Organic anions (malate, oxalate, etc.) provide extracellular sequestration of HM ions. Intracellular HM sequestration depends not only on a direct binding mechanism with different polymers (pectin, lignin, cellulose, hemicellulose, etc.) or organic anions but also on the action of cellular receptors and transmembrane transporters. We focused on the functioning chloroplasts, mitochondria, and the Golgi complex under HM stress. The currently known molecular mechanisms of plant tolerance to the toxic effects of HMs are analyzed.

Exogenous Oxalic Acid Protects Germinating Chickpea Seeds Against Cadmium Injury

“…This effect should be attributed, at least in part, to the restriction of Cd 2+ accumulation in seedling tissues, as well as the protection of sensitive biomolecules, such as proteins from decarboxylation and membrane lipids from peroxidation (El Rasafi et al 2020;Sakouhi et al 2021b). Moreover, LMWOA, including OA, were suggested to be involved in the vacuolar sequestration of metal ions, limiting, thereby, their mobility within the cell (Kosakivska et al 2021). The reduction of free Cd 2+ in the cytosol may restrict the interference of the metal ions with cell division (Haider et al 2021) via the mitigation of the Cd-imposed effect on the cell division process, for instance, the inhibition of microtubule polymerization and DNA replication, and the induction of chromosomes aberrations (Kosakivska et al 2021).…”

“…Moreover, LMWOA, including OA, were suggested to be involved in the vacuolar sequestration of metal ions, limiting, thereby, their mobility within the cell (Kosakivska et al 2021). The reduction of free Cd 2+ in the cytosol may restrict the interference of the metal ions with cell division (Haider et al 2021) via the mitigation of the Cd-imposed effect on the cell division process, for instance, the inhibition of microtubule polymerization and DNA replication, and the induction of chromosomes aberrations (Kosakivska et al 2021). The detoxifying property of OA was further confirmed by fractionation analysis showing that the utmost fraction of Cr was complexed by OA in the accumulating plant Leersia hexandra (Wang et al 2012).…”

Cutting-edge spectroscopy techniques highlight toxicity mechanisms of copper oxide nanoparticles in the aquatic plant Myriophyllum spicatum

“…An interesting response was the increased Ca concentration and its distribution primarily in epidermis tissues. Studies have shown that Ca was an important part of the signaling pathway and stress response in plants, for instance with the calmodulin pathways for signaling or the formation of egg box structures for heavy metal regulation in cell walls [66], [68].…”

The Mechanism of Metal Homeostasis in Plants: A New View on the Synergistic Regulation Pathway of Membrane Proteins, Lipids and Metal Ions

“…They are mainly divided into transporters, ion channels, and receptors. As one of the serious abiotic stressors, the bioaccumulation and bioamplification of HMs in the environment pose a great threat to the plant growth and development [80]. HMs, at toxic levels, can interact with several important cellular biomolecules, such as nuclear proteins and DNA, to induce excessive increases in the synthesis of ROS, thus resulting in serious morphological, physiological, and biochemical abnormalities in plants [81].…”