Enhanced tolerance of transgenic poplar plants overexpressing γ‐glutamylcysteine synthetase towards chloroacetanilide herbicides

Abstract

A wild-type poplar hybrid and two transgenic clones overexpressing a bacterial gamma-glutamylcysteine synthetase in the cytosol or in the chloroplasts were exposed to the chloroacetanilide herbicides acetochlor and metolachlor dispersed in the soil. The transformed poplars contained higher gamma-glutamylcysteine and glutathione (GSH) levels than wild-type plants and therefore it was supposed that they would have an elevated tolerance towards these herbicides, which are detoxified in GSH-dependent reactions. Phenotypically, the transgenic and wild-type plants did not differ. The growth and the biomass of all poplar lines were markedly reduced by the two chloroacetanilide herbicides. However, the decrease of shoot and root fresh weights caused by the herbicides was significantly smaller in the transgenic than in wild-type plants. In addition, the growth rate of poplars transformed in the cytosol was reduced to a significantly lesser extent than that of wild-type plants following herbicide treatments. The effects of the two herbicides were similar. Herbicide exposures markedly increased the levels of gamma-glutamylcysteine and GSH in leaves of each poplar line. The increase in the foliar amounts of these thiols was stronger in the transgenic lines than in the wild type, particularly in the upper leaves. Considerable GST activities were detected in leaves of all poplar plants. Exposure of poplars to chloroacetanilide herbicides resulted in a marked induction of GST activity in upper leaf positions but not in middle and lower leaves. The extent of enzyme induction did not differ significantly between transgenic and wild-type poplars. Although the results show that the transgenic poplar lines are good candidates for phytoremediation purposes, the further improvement of their detoxification capacity, preferably by transformation using genes encoding herbicide-specific GST isoenzymes, seems to be the most promising way to obtain plants suitable for practical application.

Reactive Oxygen Species, Oxidative Damage, and Antioxidative Defense Mechanism in Plants under Stressful Conditions

“…Overexpression of enzyme glutathione synthetase involved in GSH biosynthesis showed no effect on GSH level and was not sufficient to improve ozone tolerance [137] and resistance to photoinhibition [138] in hybrid poplar (Populus tremula × P. alba). However, overexpression of γ-ECS showed reduced sensitivity towards cadmium stress in Indian mustard [139] and enhanced tolerance towards chloroacetanilide herbicides in poplar plants [140]. Eltayeb and coworkers [141] observed greater protection against oxidative damages imposed by various environmental stresses in transgenic potato with higher level of reduced glutathione.…”

Bioremediation of Heavy Metals from Soil and Aquatic Environment: An Overview of Principles and Criteria of Fundamental Processes

“…Many of the poplar hybrid varieties have been genetically modified with microbial catabolic genes and specific transporters for increased remediation [141,142]. For example, mercuric reductase and γ-glutamylsysteine synthetase genes showed increased resistance to Hg and Cd and Cu, respectively, through accumulation of higher concentrations of these metals [119,142].…”

“…Many of the poplar hybrid varieties have been genetically modified with microbial catabolic genes and specific transporters for increased remediation [141,142]. For example, mercuric reductase and γ-glutamylsysteine synthetase genes showed increased resistance to Hg and Cd and Cu, respectively, through accumulation of higher concentrations of these metals [119,142]. As mentioned earlier, manipulation of desired plant species with multiple genes will facilitate complete degradation of pollutants to ensure that the harvested biomass can be utilized completely for additional benefits [143].…”

Glutathione regulates ACC synthase transcription via WRKY33 and ACC oxidase by modulating mRNA stability to induce ethylene synthesis during stress

“…Previous studies have demonstrated that enhanced GSH level can significantly induce tolerance against various environmental stress conditions (Noctor et al, 1998;Zhu et al, 1999;Gullner et al, 2001; Gomez et al, Figure 1. Characterization of T4 generation AtECS lines.…”