Expression and activity of isoenzymes of superoxide dismutase in wheat roots in response to hypoxia and anoxia

Abstract

We investigated the effects of hypoxia, anoxia and reaeration on enzymatic activity and expression of superoxide dismutase (SOD) isoforms in wheat roots (Triticum aestivum L.). Neither hypoxia nor subsequent re‐aeration caused significant changes in SOD isoenzyme pattern compared with aerated controls. However, anoxia led to the appearance of additional activity bands of SOD in native gels resulting in an increase in total activity. Additional isoformic bands remained also apparent in the following recovery period. Re‐aeration following both hypoxia and anoxia resulted in an increased content of hydrogen peroxide in roots. SOD transcript and protein levels were only slightly altered in response to hypoxia. Although SOD mRNA levels were diminished, protein content of different SOD isoforms increased with duration of anoxia. Incubation of roots with cycloheximide revealed that the additional activity bands and higher SOD protein content under anoxia were not due to de novo synthesis. Crude subcellular fractionation experiments implied that the anoxia‐responsive SOD isoforms might be plastid‐associated. We suggest that SOD is a very stable enzyme which, under anoxia, accumulates relative to total protein content and remains active even after protein modification under severe environmental stress conditions.

Expression of antioxidant defense genes in mung bean (Vigna radiata L.) roots under water-logging is associated with hypoxia tolerance

“…However, plants suffer heightened oxidative stress (ROS production) when they were shifted to aerobic condition and this explains overall higher antioxidant enzymes activity in comparatively tolerant genotypes V. luteola and T 44 during water-logging and recovery as compared to susceptible genotype Pusa Baisakhi. The increases in the activity of various antioxidative enzymes under waterlogging/flooding have also been reported by other studies, viz., SOD (Biemelt et al 2000), APX (Biemelt et al 1998), GR and CAT (Ushimaru et al 1997).…”

“…Hydrogen peroxide accumulation under hypoxic conditions has been shown in the roots and leaves of Hordeum vulgare (Kalashnikov Ju et al 1994) and in wheat roots (Biemelt et al 2000). The presence of H 2 O 2 in the apoplast and in association with the plasma membrane has been visualized by transmission electron microscopy under hypoxic conditions in four plant species (Blokhina et al 2001).…”

Plant water stress: Associations between ethylene and abscisic acid response

“…Other studies during flooding stress have associated ABA accumulation with an increase in reactive oxygen species (ROS), in Glycine max (L.) Merr. roots (Van Toai and Bolles, 1991), Hordeum vulgare L. roots and leaves (Kalashnikov et al, 1994), Zea mays L. leaves (Yan et al, 1996), and Triticum aestivum L. roots (Biemelt et al, 2000), among others. A time course study in Arabidopsis thaliana (L.) Heynh.…”

Plant Antioxidative Enzymes – Case Study: In Vitro Organogenesis of Saffron (Crocus sativus L.)

“…To discriminate between several isoforms of SOD, the gels were incubated prior to staining with a 5 mM solution of H2O2 to inhibit both Cu/Zn-SOD and Fe-SOD, or with a 3 mM solution of KCN for selective inhibition of Cu/Zn-SOD [24].For peroxidase, the gel was incubated in 80 ml of a 0.2 M sodium acetate buffer (pH 4.8) in the presence of 4 ml benzidine (0.04 M at 50% methanol) for visualization and 8 m l o f 8 % H 2O2 solution as a substrate [29]. For polyphenoloxidase, incubation was performed in 50 ml of 0.2 M sodium phosphate buffer (pH 6.8), 20 ml of 0.5% L-DOPA, 0.7 ml of 3.5% (w/v) CaCl2 solution.…”

“…The major sources of superoxide formation are the reducing side of photosystem I (PSI) in chloroplasts, and the NADH-oxidoreductase complex as well as the autoxidation of reduced ubiquinone in mitochondria. Furthermore, superoxide radicals are known to be produced by an NAD(P)H-dependent microsomal and peroxisomal electron transport chains and by xanthine oxidases in peroxisomes [24].…”