Impact of Enhanced Capacity to Scavenge Reactive Oxygen Species on Cold Tolerance of Tobacco

Abstract

Editor: Patrick S. HerendeenPremise of research. Reactive oxygen species (ROS) accumulate in plant tissues when the plant is exposed to stress, causing damage to cell structure and metabolism. Plants have a variety of mechanisms to prevent such damage, including a number of enzymes that scavenge ROS. The impact of specific enzymes, however, is as yet poorly understood.Methodology. The impact on plant tolerance to cold stress of enzymes involved in scavenging ROS was explored by comparing transplastomic tobacco lines overexpressing genes encoding glutathione reductase (GR), dehydroascorbate reductase (DHAR), glutathione-S-transferase (GST), and manganese superoxide dismutase, singly or in pairwise combinations, with nontransformed (NT) tobacco.Pivotal results. Chilling to 10ЊC resulted in less photoinhibition in lines overexpressing GR alone or in combination with GST, compared to NT tobacco, but more photoinhibition in lines overexpressing DHAR alone or in combination with GR. These differences were not, however, reflected in other indicators of stress. When chilled at 4ЊC, all lines showed similar damage to NT, except under relatively high photosynthetically active radiation, in which case photoinhibition was reduced in all transplastomic lines compared to NT. Growth over several weeks in a greenhouse was inhibited in the transplastomic lines when the duration included transient cool air temperatures. When optimal air temperature was maintained, growth over a similar duration was equal in transplastomics and NT tobacco. Conclusions.These experiments suggest a subtle interaction of enhanced ROS scavenging and tolerance of chilling stress.

Elevated ROS-scavenging enzymes contribute to acclimation to UV-B exposure in transplastomic tobacco plants, reducing the role of plastid peroxidases

“…In these plants, foreign DNA is precisely targeted into the same location in the plastome and thus the inter-line variability associated with nuclear transformants can be excluded (Grant et al 2014) Plants are described in detail in Le Martret et al (2011) Flint and Caldwell (2003).…”

Transplastomic plants for innovations in agriculture. A review

“…At the same time, paraquat-induced oxidative stress tolerance could be only achieved in DHAR::gor and GST::gor plants expressing simultaneously E. coli glutathione reductase (gor) . In continuation of these works Poage et al 2011), transplastomic tobacco lines overexpressing gor, DHAR, GST, and MnSOD singly or in pairwise combinations were exposed to low temperatures (Grant et al 2014). Only gor and GST::gor plants had decreased photoinhibition at 10°C when compared to non-transformed plants, while DHAR and DHAR::gor plants had increased photoinhibition.…”

Tolerance of Transplastomic Tobacco Plants Overexpressing a Theta Class Glutathione Transferase to Abiotic and Oxidative Stresses

“…GSTs have been used before in chloroplast transformation; The Sj GST26 (EC:2.5.1.18), from Schistomosoma japonicum (Smith and Johnson, 1988) and His-tagged derivative of the maltose- binding protein (His 6 -MBP) were expressed in tobacco chloroplasts to be used as affinity tags for the rapid purification of chloroplast-expressed proteins (Ahmad et al, 2012). Transplastomic tobacco lines overexpressing glutathione reductase (GR) alone or combined with GST were more tolerant under 10°C, whereas lines overexpressing dehydroascorbate reductase (DHAR) alone or in combination with GR were more sensitive compared to wild type plants (Grant et al, 2014). When these lines were chilled at 4°C and under relatively high photosynthetically active radiation (PAR), all lines were more sensitive compared to wild type plants, indicating that overexpression of the ROS-scavenging enzymes may be dependent on the interaction of light and cold stress (Grant et al, 2014).…”