Nitric Oxide Impact on Plant Adaptation to Transition Metal Stress

Abstract

Nitric oxide (NO), a gaseous bioactive messenger molecule, regulates diverse array of physiological processes ranging from seed germination, growth, flowering to the biotic and abiotic stress responses. Transition metals such as manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni) copper (Cu), and zinc (Zn) are essential micronutrient for normal growth and development of living organisms. Although essential in trace amounts, at higher levels these metals can be toxic to cells because they directly or indirectly influence DNA, protein, and membrane integrity and function. The biological actions of NO and its derivatives exerted through the binding to transition metals of metalloproteins, and covalent modifications of cysteine and tyrosine residues. The presence of transition metal influences the endogenous NO levels and thereby modulates several metabolic processes. Depending on the type of plant tissue and concentrations, the NO can elicit both beneficial and deleterious effects. Recently, several articles have proclaimed the alleviation of transition metal toxicity by exogenous application of NO. The present article discusses the recent understanding of the endogenous and exogenous NO to essential transition metal tolerance.