title: Hydrogen Peroxide Pretreatment Mitigates Cadmium-Induced Oxidative Stress inBrassica napusL.: An Intrinsic Study on Antioxidant Defense and Glyoxalase Systems.
abstract: Cadmium (Cd) is considered as one of the most toxic metals for plant growth and development. In the present study, we investigated the role of externally applied hydrogen peroxide (H2O2) in regulating the antioxidant defense and glyoxalase systems in conferring Cd-induced oxidative stress tolerance in rapeseed (Brassica napusL.). Seedlings were pretreated with 50 μM H2O2for 24 h. These pretreated seedlings as well as non-pretreated seedlings were grown for another 48 h at two concentrations of CdCl2(0.5 and 1.0 mM). Both the levels of Cd increased MDA and H2O2levels and lipoxygenase activity while ascorbate (AsA) declined significantly. However, reduced glutathione (GSH) content showed an increase at 0.5 mM CdCl2, but glutathione disulfide (GSSG) increased at any level of Cd with a decrease in GSH/GSSG ratio. The activities of ascorbate peroxidase (APX) and glutathioneS-transferase (GST) upregulated due to Cd treatment in dose-dependent manners, while glutathione reductase (GR) and glutathione peroxidase (GPX) increased only at 0.5 mM CdCl2and decreased at higher dose. The activity of monodehydroascorbate reductase (MDHAR), dehydroascorbate reductase (DHAR), catalase (CAT), glyoxalase I (Gly I), and glyoxalase II (Gly II) decreased under Cd stress. On the other hand, H2O2pretreated seedlings, when exposed to Cd, AsA and GSH contents and GSH/GSSG ratio increased noticeably. H2O2pretreatment increased the activities of APX, MDHAR, DHAR, GR, GST, GPX, and CAT of Cd affected seedlings. Thus enhancement of both the non-enzymatic and enzymatic antioxidants helped to decrease the oxidative damage as indicated by decreased levels of H2O2and MDA. The seedlings which were pretreated with H2O2also showed enhanced glyoxalase system. The activities of Gly I, and Gly II and the content of GSH increased significantly due to H2O2pretreatment in Cd affected seedlings, compared to the Cd-stressed plants without H2O2pretreatment which were vital for methylglyoxal detoxification. So, the major roles of H2O2were improvement of antioxidant defense system and glyoxalase system which protected plants from the damage effects of ROS and MG. The mechanism of H2O2to induce antioxidant defense and glyoxalase system and improving physiology under stress condition is not known clearly which should be elucidated. The signaling roles of H2O2and its interaction with other signaling molecules, phytohormones or other biomolecules and their roles in stress protection should be explored.
authors.affiliation: Department of Agronomy, Faculty of Agriculture, Sher-e-Bangla Agricultural University Sher-e-Bangla Nagar, Bangladesh.
authors.forename: Mirza
authors.initials: M
authors.lastname: Hasanuzzaman
authors.affiliation: Department of Agricultural Botany, Faculty of Agriculture, Sher-e-Bangla Agricultural UniversitySher-e-Bangla Nagar, Bangladesh; Laboratory of Plant Stress Responses, Department of Applied Biological Science, Faculty of Agriculture, Kagawa UniversityMiki-cho, Japan.
authors.forename: Kamrun
authors.initials: K
authors.lastname: Nahar
authors.affiliation: Stress Physiology and Molecular Biology Laboratory, Centre for Biotechnology, Maharshi Dayanand University Rohtak, India.
authors.forename: Sarvajeet S
authors.initials: SS
authors.lastname: Gill
authors.affiliation: Department of Biological Sciences, Faculty of Science, King Abdulaziz University Jeddah, Saudi Arabia.
authors.forename: Hesham F
authors.initials: HF
authors.lastname: Alharby
authors.affiliation: Department of Subtropical Agro-Environmental Sciences, Faculty of Agriculture, University of the Ryukyus Nishihara, Japan.
authors.forename: Bam H N
authors.initials: BH
authors.lastname: Razafindrabe
authors.affiliation: Laboratory of Plant Stress Responses, Department of Applied Biological Science, Faculty of Agriculture, Kagawa University Miki-cho, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Fujita
keywords: abiotic stress; antioxidant defense; cross tolerance; metal toxicity; methylglyoxal; oxidative stress; signaling molecule