Multi-Component Antioxidative System and Robust Carbohydrate Status, the Essence of Plant Arsenic Tolerance

Abstract

Arsenic (As) contaminates the food chain and decreases agricultural production through impairing plants, particularly due to oxidative stress. To better understand the As tolerance mechanisms, two contrasting tobacco genotypes: As-sensitive Nicotiana sylvestris and As-tolerant N.tabacum, cv. ‘Wisconsin’ were analyzed. The most meaningful differences were found in the carbohydrate status, neglected so far in the As context. In the tolerant genotype, contrary to the sensitive one, net photosynthesis rates and saccharide levels were unaffected by As exposure. Importantly, the total antioxidant capacity was far stronger in the As-tolerant genotype, based on higher antioxidants levels (e.g., phenolics, ascorbate, glutathione) and activities and/or appropriate localizations of antioxidative enzymes, manifested as reverse root/shoot activities in the selected genotypes. Accordingly, malondialdehyde levels, a lipid peroxidation marker, increased only in sensitive tobacco, indicating efficient membrane protection in As-tolerant species. We bring new evidence of the orchestrated action of a broad spectrum of both antioxidant enzymes and molecules essential for As stress coping. For the first time, we propose robust carbohydrate metabolism based on undisturbed photosynthesis to be crucial not only for subsidizing C and energy for defense but also for participating in direct reactive oxygen species (ROS) quenching. The collected data and suggestions can serve as a basis for the selection of plant As phytoremediators or for targeted breeding of tolerant crops.

Arsenic Toxicity-Induced Physiological and Metabolic Changes in the Shoots of Pteris cretica and Spinacia oleracea

“…Arsenic can affect photosynthetic pigments, the membrane system of chloroplasts, and chlorophyll fluorescence, thus reducing photosynthetic activity [ 58 ]. The As toxicity leads to a decrease in chlorophyll among different plant species [ 8 , 24 , 37 , 39 , 40 , 45 , 59 ]. Our results confirmed this effect of As on Chl tot content in S. oleracea shoots, while in P. cretica shoots, the adverse As effect was not significant ( Table 3 ).…”

“…Plants’ intake of As can hardly be downregulated, as it is often mediated by essential element transporters [ 8 ]. Arsenic exposure has an adverse effect on the morphological (e.g., chlorosis), physiological (e.g., growth processes inhibition), and biochemical (e.g., oxidative stress) responses of plants [ 9 , 10 ].…”

“…To avoid As toxicity, tolerant plants utilise various strategies, such as reducing the concentration of toxic elements at sensitive sites inside a plant cell [ 5 ]. Once inside the plant cell, most As(V) is reduced to As(III), as only the trivalent form can undergo detoxification [ 8 ]. The cellular detoxification of As(III) in non-As-hyperaccumulators involves As complexation with phytochelatins respectively nonprotein thiols and storage of these complexes in vacuoles [ 26 , 27 ], and can be characterized as adaptive resistance.…”

Investigation of an Antioxidative System for Salinity Tolerance in Oenanthe javanica

“…Total polyphenols not only induce activities of antioxidant enzymes, but also assist as antioxidants themselves under abiotic stress conditions [ 73 , 74 ]. In the present study, the content of total polyphenols and flavonoids increased significantly in V11E002 compared to its counterparts.…”

Enzymatic and Non-Enzymatic Molecules with Antioxidant Function

“…Kofroňová et al investigated As tolerance mechanisms utilizing tobacco plants As-sensitive and As-tolerant. The total antioxidant capacity was far stronger in the As-tolerant genotype, showing higher antioxidants levels (phenolics, ascorbate, GSH) [ 14 ]. Moreover, malondialdehyde levels, a lipid peroxidation marker, increased only in As-sensitive plants.…”