Reactive oxygen species and antioxidant machinery in abiotic stress tolerance in crop plants

Soil Chemical Analysis

Reactive oxygen species (ROS) are produced as a normal product of plant cellular metabolism. Various environmental stresses lead to excessive production of ROS causing progressive oxidative damage and ultimately cell death. Despite their destructive activity, they are well-described second messengers in a variety of cellular processes, including conferment of tolerance to various environmental stresses. Whether ROS would serve as signaling molecules or could cause oxidative damage to the tissues depends on the delicate equilibrium between ROS production, and their scavenging. Efficient scavenging of ROS produced during various environmental stresses requires the action of several nonenzymatic as well as enzymatic antioxidants present in the tissues. In this paper, we describe the generation, sites of production and role of ROS as messenger molecules as well as inducers of oxidative damage. Further, the antioxidative defense mechanisms operating in the cells for scavenging of ROS overproduced under various stressful conditions of the environment have been discussed in detail.

https://downloads.hindawi.com/archive/2012/217037.pdf

Reactive Oxygen Species, Oxidative Damage, and Antioxidative Defense Mechanism in Plants under Stressful Conditions

Water deficit and salinity, especially under high light intensity or in combination with other stresses, disrupt photosynthesis and increase photorespiration, altering the normal homeostasis of cells and cause an increased production of reactive oxygen species (ROS). ROS play a dual role in the response of plants to abiotic stresses functioning as toxic by-products of stress metabolism, as well as important signal transduction molecules. In this review, we provide an overview of ROS homeostasis and signalling in response to drought and salt stresses and discuss the current understanding of ROS involvement in stress sensing, stress signalling and regulation of acclimation responses.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-3040.2009.02041.x

Reactive oxygen species homeostasis and signalling during drought and salinity stresses

Heavy metals such as Cu and Zn are essential for normal plant growth, although elevated concentrations of both essential and non-essential metals can result in growth inhibition and toxicity symptoms. Plants possess a range of potential cellular mechanisms that may be involved in the detoxification of heavy metals and thus tolerance to metal stress. These include roles for the following: for mycorrhiza and for binding to cell wall and extracellular exudates; for reduced uptake or efflux pumping of metals at the plasma membrane; for chelation of metals in the cytosol by peptides such as phytochelatins; for the repair of stress-damaged proteins; and for the compartmentation of metals in the vacuole by tonoplast-located transporters. This review provides a broad overview of the evidence for an involvement of each mechanism in heavy metal detoxification and tolerance.

/pdf/cellular-mechanisms-for-heavy-metal-detoxification-and-13u1e0uypi.pdf

Cellular mechanisms for heavy metal detoxification and tolerance

Heavy metal hyperaccumulating plants: how and why do they do it? And what makes them so interesting?

We analyzed antioxidative defenses, photosynthesis, and pigments (especially xanthophyll-cycle components) in two wheat ( Triticum durum Desf.) cultivars, Adamello and Ofanto, during dehydration and rehydration to determine the difference in their sensitivities to drought and to elucidate the role of different protective mechanisms against oxidative stress. Drought caused a more pronounced inhibition in growth and photosynthetic rates in the more sensitive cv Adamello compared with the relatively tolerant cv Ofanto. During dehydration the glutathione content decreased in both wheat cultivars, but only cv Adamello showed a significant increase in glutathione reductase and hydrogen peroxide-glutathione peroxidase activities. The activation states of two sulfhydryl-containing chloroplast enzymes, NADP + -dependent glyceraldehyde-3-phosphate dehydrogenase and fructose-1,6-bisphosphatase, were maintained at control levels during dehydration and rehydration in both cultivars. This indicates that the defense systems involved are efficient in the protection of sulfhydryl groups against oxidation. Drought did not cause significant effects on lipid peroxidation. Upon dehydration, a decline in chlorophyll a , lutein, neoxanthin, and β-carotene contents, and an increase in the pool of de-epoxidized xanthophyll-cycle components (i.e. zeaxanthin and antheraxanthin), were evident only in cv Adamello. Accordingly, after exposure to drought, cv Adamello showed a larger reduction in the actual photosystem II photochemical efficiency and a higher increase in nonradiative energy dissipation than cv Ofanto. Although differences in zeaxanthin content were not sufficient to explain the difference in drought tolerance between the two cultivars, zeaxanthin formation may be relevant in avoiding irreversible damage to photosystem II in the more sensitive cultivar.

http://www.plantphysiol.org/content/plantphysiol/119/3/1091.full.pdf

Antioxidative Defense System, Pigment Composition, and Photosynthetic Efficiency in Two Wheat Cultivars Subjected to Drought

Trace element behaviour at the root-soil interface: Implications in phytoremediation

Antioxidative responses of Calendula officinalis under salinity conditions

The effects of in vivo copper on the lipid composition of root plasma membrane and the activities of membrane-bound enzymes, such as NADPH-dependent oxidases and lipoxygenase, were studied. Plants were grown in hydroponic culture for 11 d without Cu supply or in the presence of 50 microM Cu. Control plants were supplied with 0.3 microM Cu. Growth of roots was severely affected in the 50 microM Cu-grown plants, whereas roots grown in Cu-deficient solution did not show any difference in comparison with the control. The 50 microM Cu concentration caused an increase in the leakage of K(+) ions as well. Excess metal supply resulted in a decrease in the total lipid content of plasma membrane, a higher phospholipid amount and a reduction of steryl lipids (free sterols, steryl glycosides and acylated steryl glycosides). Cu depletion in the growth solution had only a slight effect on the plasma membrane lipid composition. In comparison with the control, only the excess of Cu caused a decrease in the lipid to protein ratio as well as a change in the phospholipid composition, with a lower phosphatidylcholine to phosphatidylethanolamine ratio. The degree of unsaturation of root plasma membranes decreased following the 0 Cu treatment and even more after the 50 microM Cu supply. Plasma membranes of wheat grown under metal deficiency and excess showed increased NADPH-dependent superoxide-producing oxidase activities, whereas membrane-bound lipoxygenase was not increased or activated due to Cu treatments. The consequences of changes in plasma membrane lipid composition and activated oxygen production as a result of Cu treatments are discussed.

Flavia Navari-Izzo

Papers

Heavy metal hyperaccumulating plants: how and why do they do it? And what makes them so interesting?

Antioxidative Defense System, Pigment Composition, and Photosynthetic Efficiency in Two Wheat Cultivars Subjected to Drought

Trace element behaviour at the root-soil interface: Implications in phytoremediation

Antioxidative responses of Calendula officinalis under salinity conditions

Lipids and NADPH-dependent superoxide production in plasma membrane vesicles from roots of wheat grown under copper deficiency or excess