Ascorbate-Mediated Modulation of Cadmium Stress Responses: Reactive Oxygen Species and Redox Status in Brassica napus

Abstract

The role of ascorbate (AsA) in antioxidant defense system-associated resistance to cadmium (Cd) in oilseed rape plants has not yet been clearly demonstrated. The present study investigated the critical role of exogenous AsA on the physiological and biochemical responses of reactive oxygen species (ROS) and antioxidant scavenging defense systems in oilseed rape (Brassica napus L. cv. Tammi) seedlings exposed to Cd. Cd (10 μM) treatment led to significant reductions in plant growth; increases in the levels of superoxide anion radical, hydrogen peroxide, and malondialdehyde; and increases in Cd uptake and accumulation by the roots and shoots in hydroponically grown 10-day-old seedlings. Moreover, it reduced AsA content and AsA redox ratios, which have been correlated with reductions in glutathione (GSH) and/or nicotinamide adenine dinucleotide phosphate (NADPH) redox status. However, exogenously applying AsA to Cd-exposed seedlings decreased Cd-induced ROS, improved antioxidant defense systems by increasing AsA, GSH, and NADPH contents, and increased Cd uptake and accumulation in both roots and shoots of the plants. These results provided evidence that the enhancement in AsA redox status can be linked to an increase in the GSH and/or NADPH redox ratios through the induction of the AsA–GSH–NADPH cycle. Thus, these results suggest that exogenous AsA application to oilseed rape seedlings under Cd stress might alleviate the overall Cd toxicity by regulating the homeostasis of the AsA–GSH–NADPH cycle, which reestablishes the steady-state cellular redox status.

Comparative Physiological and Transcriptomic Analyses Reveal Ascorbate and Glutathione Coregulation of Cadmium Toxicity Resistance in Wheat Genotypes

“…7). A previous study showed that spraying ASA alone could alleviate Cd-induced oxidative stress in rapeseed plants, while only the aboveground biomass was signi cantly affected [54]. This is similar to our results that the effect of AsA on the root biomass was slight (Fig.…”

Exogenous 6-Benzyladenine Improves Waterlogging Tolerance in Maize Seedlings by Mitigating Oxidative Stress and Upregulating the Ascorbate-Glutathione Cycle

“…Plants minimize the accumulation of ROS via complex and highly efficient enzymatic and non-enzymatic antioxidants (Ahmad et al, 2010(Ahmad et al, , 2019Kohli et al, 2019). Specifically, the ascorbate-glutathione (AsA-GSH) cycle has been reported to reduce the negative impact of ROS (Jung et al, 2020;Tan et al, 2020;. The AsA-GSH cycle consists of the enzymes ascorbate peroxidase (APX), glutathione reductase (GR), monodehydroascorbate reductase (MDHAR), and dehydroascorbate reductase (DHAR), and the non-enzymatic molecules ascorbic acid (AsA), dehydroascorbic acid (DHA), reduced glutathione (GSH), and oxidized glutathione (GSSG) (Ahmad et al, 2010(Ahmad et al, , 2019Kohli et al, 2019).…”

Thermal Analysis of Stomatal Response under Salinity and High Light

“…Leaf water content was determined by measuring the rosette mass before (F w ) and after drying (D w ) in an oven at 105 °C for 1.5 h. Water content (WC) was calculated according to the following Equation (1): WC(%) = 100·(F w − D w )/F w , where F w and D w mean a fresh and a dry mass, respectively [ 69 ].…”