Enhanced tolerances of transgenic tobacco plants expressing both superoxide dismutase and ascorbate peroxidase in chloroplasts against methyl viologen‐mediated oxidative stress

Abstract

In order to better understand the role of antioxidant enzymes in plant stress protection mechanisms, transgenic tobacco ( Nicotiana tabacum cv. Xanthi) plants were developed that overexpress both superoxide dismutase (SOD) and ascorbate peroxidase (APX) in chloroplasts. These plants were evaluated for protection against methyl viologen (MV, paraquat)-mediated oxidative damage both in leaf discs and whole plants. Transgenic plants that express either chloroplast-targeted CuZnSOD (C) or MnSOD (M) and APX (A) were developed (referred to as CA plants and AM plants, respectively). These plant lines were crossed to produce plants that express all three transgenes (CMA plants and AMC plants). These plants had higher total APX and SOD activities than non-transgenic (NT) plants and exhibit novel APX and SOD isoenzymes not detected in NT plants. As expected, transgenic plants that expressed single SODs showed levels of protection from MV that were only slightly improved compared to NT plants. The expression of either SOD isoform along with APX led to increased protection while expression of both SODs and APX provided the highest levels of protection against membrane damage in leaf discs and visual symptoms in whole plants.

Modification of reactive oxygen species scavenging capacity of chloroplasts through plastid transformation

“…This finding runs counter to some previous observations (e.g. Slooten et al 1995, McKersie et al 1999, Kwon et al 2002), on nuclear transformants, which suggest that over-expression of chloroplast-targeted SODs suppresses the activity of the native enzymes, although this finding is far from universal among the various SOD over-expressing lines. In fact there are two publications which support our observation.…”

“…Thus, Aono et al (1995) crossed transgenic tobacco plants overexpressing SOD or GR and demonstrated a higher level of tolerance to MV-induced oxidative stress in the hybrids, compared to that of either parent. Similarly, SOD and APX have proven an effective combination in transgenic tobacco (Kwon et al 2002;Kim et al 2005), potato (Tang et al 2006) and tall fescue (Lee et al 2007a). In one study with tobacco (Lee et al 2007b) three components of the ROS defence network (SOD, APX and DHAR) were shown to provide further improvements in tolerance to salinity and MV, in comparison with plants over-expressing only the first two of these.…”

<b>‘Desiccation tolerance of <i>Rhamnidium elaeocarpum</i> Reissek (Rhamnaceae) seeds

“…Therefore, antioxidant compounds and enzymes are of particular importance for seed development (GARNCZARSKA et al, 2009). The activity of antioxidant enzymes protects tissues against oxidative damage due to water loss in species that are tolerant to desiccation (ILLING et al, 2005), and several reports have described the synergistic action of the simultaneous expression of free-radical remover enzymes on desiccation tolerance in seeds (KWON et al, 2002).…”

Response to biotic and oxidative stress in Arabidopsis thaliana: Analysis of variably phosphorylated proteins

“…In particular, plant leaves were treated with i) chitosan, a cell wall component of many fungi able to induce oxidative burst and defense proteins synthesis [10]; ii) benzothiadiazole, a compound known to activate a number of SAR-associated genes and leading to enhanced plant protection against various pathogens [11]; iii) mechanical injury/wounding, mimicking physical damage by insects/herbivores and known to induce the transcription of wound-responsive genes [12]; iv) methyl viologen (MV), a powerful inducer of oxidative stress, known to be a component of the defense responses [13]. Thus, phosphorylated proteins were enriched by Metal Oxide Affinity Chromatography (MOAC), resolved by 2-DE and resulting proteomic patterns were compared.…”