Exogenous Silicon Attenuates Cadmium-Induced Oxidative Stress in Brassica napus L. by Modulating AsA-GSH Pathway and Glyoxalase System

Abstract

Cadmium (Cd) brings a devastating health hazard to human being as a serious consequence of agricultural and environmental contamination. We demonstrated the protective effect of silicon (Si) on cadmium (Cd)-stressed rapeseed (Brassica napus L. cv. BINA Sharisha 3) plants through regulation of antioxidant defense and glyoxalase systems. Twelve-day-old seedlings were exposed to Cd stress (0.5 and 1.0 mM CdCl2) separately and in combination with Si (SiO2, 1.0 mM) for 2 days. Cadmium toxicity was evident by an obvious oxidative stress through sharp increases in H2O2 content and lipid peroxidation (malondialdehyde, MDA content), and visible sign of superoxide and H2O2. Cadmium stress also decreased the content of ascorbate (AsA) and glutathione (GSH) as well as their redox pool. The activities of monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR) and catalase (CAT) were decreased by Cd while ascorbate peroxidase (APX) and glutathione S-transferase (GST) activities were increased. The enzymes of glyoxalase system (glyoxalase I, Gly I and glyoxalase II, Gly II) were also inefficient under Cd stress. However, exogenous application of Si in Cd treated seedlings reduced H2O2 and MDA contents and improved antioxidant defense mechanism through increasing the AsA and GSH pools and activities of AsA-GSH cycle (APX, MDHAR, DHAR and GR) and glyoxalase system (Gly I and Gly II) enzymes and CAT. Thus Si reduced oxidative damage in plants to make more tolerant under Cd stress through augmentation of different antioxidant components and methylglyoxal detoxification system.

Modulating the antioxidant system by exogenous 2-(3,4-dichlorophenoxy) triethylamine in maize seedlings exposed to polyethylene glycol-simulated drought stress

“…Higher contents of AsA and GSH correspond to reduced ROS-associated injuries in plants [47]. The AsA-GSH cycle is the key defence mechanism for regulating the oxidative and reductive environments via the modulation of the interconversion of AsA/DHA and GSH/GSSG in the foliar tissues of higher plants [48]. …”

The controversies of silicon's role in plant biology

“…Oxidative stress is a hallmark feature of stress (Mittler, ; Apel & Hirt, ; Gill & Tuteja, ) and its reduction by Si, by upregulating antioxidant activity, is a proposed major mode of action (Liang, ; Liang et al ., , ; Zhu et al ., ; Gong et al ., ; Gunes et al ., ; Farooq et al ., ; Hasanuzzaman et al ., ; Kim et al ., ; cf. Mateos‐Naranjo et al ., ).…”

“…[Correction added after online publication 14 July 2018: 'heavy' has been deleted from the preceding sentence.] Oxidative stress is a hallmark feature of stress (Mittler, 2002;Apel & Hirt, 2004;Gill & Tuteja, 2010) and its reduction by Si, by upregulating antioxidant activity, is a proposed major mode of action (Liang, 1999;Liang et al, 2003Liang et al, , 2006Zhu et al, 2004;Gong et al, 2005;Gunes et al, 2007;Farooq et al, 2016;Hasanuzzaman et al, 2017;Kim et al, 2017;cf. Mateos-Naranjo et al, 2015).…”

Role of Ascorbic acid, Glutathione and Proline Applied as Singly or in Sequence Combination in Improving Chickpea Plant through Physiological Change and Antioxidant Defense under Different Levels of Irrigation Intervals

“…AsA play a vital role in photosynthesis and proline synthesis [38]. Also, AsA can quench ROS resulted from water stress and help in the maintenance of chlorophyll content which stimulates the level of plant growth [39]. Exogenous proline can interact with enzymes to preserve protein structures and activities [40] and play a critical role in protecting photosynthetic activity [41].…”