Modulation of antioxidant machinery in α-tocopherol-enriched transgenic Brassica juncea plants tolerant to abiotic stress conditions

Abstract

The antioxidant machinery in plants consists of several components with unique or overlapping functions that combat the deleterious production of reactive oxygen species (ROS) induced by stress conditions. Tocopherols are a group of powerful antioxidants having additional roles in signaling and gene expression, with α-tocopherol being the most potent form. In the present study, we used wild-type (WT) and α-tocopherol-enriched transgenic (TR) Brassica juncea plants grown under salt, heavy metal, and osmotic stress to compare their relative tolerance to these stresses and to assess the effects of increased α-tocopherol content on the other antioxidative enzymes and molecules. The oxidative damage caused by induced stress was lower in TR plants compared to WT plants as assessed by their higher relative water content and lower electrolyte leakage, malondialdehyde content as well as H(2)O(2) accumulation. Lesser superoxide and H(2)O(2) accumulation was also observed by histochemical staining in TR seedlings exposed to stress. Though no significant differences were evident under normal growth conditions, TR plants showed higher activities and transcript levels of antioxidant enzymes superoxide dismutase, catalase, ascorbate peroxidase, and glutathione reductase than WT plants under similar stress conditions. A decrease in ascorbate and glutathione content with marginally higher reductive ratios of these compounds was also observed in TR plants under the stress conditions. Our findings implicate the role of higher α-tocopherol levels in conferring better tolerance against salt, heavy metal, and osmotic stresses and also establish the existence of interplay between this lipid-soluble antioxidant and other water-soluble components of plant antioxidant defense.

Overexpression of Ferredoxin, PETF, Enhances Tolerance to Heat Stress in Chlamydomonas reinhardtii

“…Reduction of ROS level is a major biotechnology strategy used to protect plants from various abiotic stresses [38–40]. In the study reported herein, ROS produced by C. reinhardtii cause oxidative damage, which results in cell death under heat treatment at 42 °C for 40 min.…”

Heavy Metal-Induced Oxidative Stress in Plants: Response of the Antioxidative System

“…For example, overexpression of the γ-tocopherol methyl transferase gene from A. thaliana in transgenic Brassica juncea plants resulted in an over sixfold increase in the level of α-toc, induced by a variety of abiotic stresses (Yusuf and Sarin 2007). Moreover, α-toc-enriched transgenic B. juncea was found to increase the tocopherol levels which enhanced its tolerance against Cd-induced stress (Kumar et al 2013). Also, some other transgenic plants, such as potato, with the reduced expression of some other proteins, e.g., manganese stabilizing protein, an important component of the PSII, were found to accumulate α-toc and other antioxidants as a consequence of Zn treatment (Gururani et al 2013).…”

Membrane targeting of MnSOD is essential for oxidative stress tolerance of nitrogen-fixing cultures of Anabaena sp. strain PCC7120

“…The staining procedure followed was a modification of that used for plant leaves (Kumar et al 2013). Three-dayold nitrogen-fixing and nitrogen-supplemented cultures of recombinant Anabaena strains, AnpAM and AnsodA + were inoculated in the corresponding fresh growth medium at 1 µg chlorophyll a density mL −1 in the absence or presence of 0.2 µM methyl viologen.…”