Abiotic Stress Response to As and As+Si, Composite Reprogramming of Fruit Metabolites in Tomato Cultivars

Impact of Silicon Nanoparticles on the Antioxidant Compounds of Tomato Fruits Stressed by Arsenic

Tomato fruit is rich in antioxidant compounds such as lycopene and β-carotene. The beneficial effects of the bioactive compounds of tomato fruit have been documented as anticancer activities. The objective of this research was to determine whether arsenic (As) causes changes in the content of antioxidant compounds in tomato fruits and whether Silicon nanoparticles (SiO₂ NPs) positively influence them. The effects on fruit quality and non-enzymatic antioxidant compounds were determined. The results showed that As decreased the oxide-reduction potential (ORP), while lycopene and β-carotene were increased by exposure to As at a low dose (0.2 mg L^-1), and proteins and vitamin C decreased due to high doses of As in the interaction with SiO₂ NPs. A dose of 250 mg L^-1 of SiO₂ NPs increased glutathione and hydrogen peroxide (H₂O₂), and phenols decreased with low doses of As and when they interacted with the NPs. As for the flavonoids, they increased with exposure to As and SiO₂ NPs. The total antioxidant capacity, determined by the ABTS (2,2´-azino-bis[3-ethylbenzthiazolin-6-sulfonic acid]) test, showed an increase with the highest dose of As in the interaction with SiO₂ NPs. The application of As at low doses induced a greater accumulation of bioactive compounds in tomato fruit; however, these compounds decreased in high doses as well as via interaction with SiO₂ NPs, indicating that there was an oxidative burst.

Strong antioxidant capacity of horseradish hairy root cultures under arsenic stress indicates the possible use of Armoracia rusticana plants for phytoremediation

The potential contamination of the food chain is the most important aspect of arsenic (As) pollution, since it is highly toxic to all organisms. Thus, the search for As hyperaccumulators suitable to remove As from contaminated soils appears to be a vital task. Horseradish (Armoracia rusticana), a crop plant with a high potential to accumulate heavy metals, can also serve to study the physiological processes that accompany arsenic stress. The significant adverse effect caused by arsenic exposure is an oxidative stress. Plants have developed a highly organized system to quench free radicals, which includes the action of both enzymatic and non-enzymatic quenching. Saccharides are proposed to possess outstanding antioxidant activity in vitro, and thus, they are likely to effectively quench free radicals also in plant tissues. In this study, root cultures (hairy root type) of horseradish were grown in vitro on media with different concentrations of arsenic (5-60 µg l^-1). Arsenic slowed down the growth, nevertheless up to three-fold biomass increase was achieved at the highest dose. Moreover, root tissues were able to remove as much as 75% of arsenic from the cultivation medium within 7 days. We also evaluated diverse oxidative-stress-related features: contents of reactive oxygen species, the activities of key antioxidant enzymes, and the contents of important antioxidant molecules, such as glutathione, proline, phenolic compounds and non-structural carbohydrates. At all arsenic treatments, we observed a significant proline content increase and enhanced antioxidant enzymes (peroxidase, catalase and glutathione-S-transpherase) activities peaking, however, at different doses. Soluble carbohydrates contents also significantly increased after 7-day treatment a then decreased nearly to the original levels. This study points to efficient antioxidant system of horseradish hairy roots enabling good growth and substantial As accumulation even under high As exposure. Providing that horseradish shares these important features with this model system, we could propose that horseradish is a promising candidate to exploit in arsenic phytoremediation.

Get the Balance Right: ROS Homeostasis and Redox Signalling in Fruit

Plant central metabolism generates reactive oxygen species (ROS), which are key regulators that mediate signalling pathways involved in developmental processes and plant responses to environmental fluctuations. These highly reactive metabolites can lead to cellular damage when the reduction-oxidation (redox) homeostasis becomes unbalanced. Whilst decades of research have studied redox homeostasis in leaves, fundamental knowledge in fruit biology is still fragmentary. This is even more surprising when considering the natural profusion of fruit antioxidants that can process ROS and benefit human health. In this review, we explore redox biology in fruit and provide an overview of fruit antioxidants with recent examples. We further examine the central role of the redox hub in signalling during development and stress, with particular emphasis on ascorbate, also referred to as vitamin C. Progress in understanding the molecular mechanisms involved in the redox regulations that are linked to central metabolism and stress pathways will help to define novel strategies for optimising fruit nutritional quality, fruit production and storage.