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

Abstract

Chloroplasts are organelles subjected to extreme oxidative stress conditions. Biomolecules produced in the chloroplasts act as signals guiding plant metabolism toward stress tolerance and play a major role in regulating gene expression in the nucleus. Herein, we used transplastomic plants as an alternative approach to expression of transgenes in the nucleus for conferring stress tolerance to abiotic stresses and herbicides. To investigate the morphophysiological and molecular mechanisms and the role of plastid expressed GSTs in tobacco stress detoxification and stress tolerance, we used transplastomic tobacco lines overexpressing a theta class glutathione transferase (GST) in chloroplasts. The transplastomic plants were tested under drought (0, 100, and 200 mM mannitol) and salinity (0, 150, and 300 mM NaCl) in vitro, and under herbicide stress (Diquat). Our results suggest that ptAtGSTT lines were tolerant to herbicide-induced oxidative and salinity stresses and showed enhanced response tolerance to mannitol-induced osmotic stress compared to WT plants. Overexpression of the Arabidopsis thaliana AtGSTT in the chloroplasts resulted in enhanced photo-tolerance and turgor maintenance under stress. Whole-genome transcriptome analysis revealed that genes related to stress tolerance, were upregulated in ptAtGSTT2a line under both control and high mannitol stress conditions. Transplastomic plants overexpressing the ptAtGSTT2a in the chloroplast showed a state of acclimation to stress, as only limited number of genes were upregulated in the ptAtGSTT2a transplastomic line compared to WT under stress conditions while at the same time genes related to stress tolerance were upregulated in ptAtGSTT2a plants compared to WT in stress-free conditions. In parallel, the metabolic profile indicated limited perturbations of the metabolic homeostasis in the transplastomic lines and greater accumulation of mannitol, and soluble sugars under high mannitol stress. Therefore, transplastomic lines seem to be in a state of acclimation to stress under stress-free conditions, which was maintained even under high mannitol stress. The results help to elucidate the role of GSTs in plant abiotic stress tolerance and the underlying mechanisms of the GSTs expressed in the chloroplast, toward environmental resilience of cultivated crops.

Directed Evolution of a Glutathione Transferase for the Development of a Biosensor for Alachlor Determination

“…2.5.1.18) are a widely spread family of enzymes found in both eukaryotes and prokaryotes [1,2]. They catalyze the conjugation of glutathione (GSH) with a range of hydrophobic xenobiotic compounds such as drugs, environmental pollutants, and pesticides, including chloroacetanilide herbicides [3][4][5][6][7][8][9]. Their catalytic versatility and wide-substrate specificity stem from their structural flexibility and active-site plasticity [3,[10][11][12][13].…”

Full-length transcriptome analysis of multiple organs and identification of adaptive genes and pathways in Mikania micrantha

“…The overexpression of Tau and Phi GSTs contributes to plant tolerance to a variety of abiotic stresses, such as dehydration, high salinity, heavy metals, and oxygen stress 48 , 49 . Zeta GSTs enhance plant growth and germination at low temperature, and Theta GSTs confer tolerance to abiotic and oxidative stresses in tobacco plants 50 , 51 . The GHR and DHAR subfamilies are also important components of the GST gene family, whose members are up-regulated or differentially regulated under high-temperature, drought, and other abiotic stresses 52 , 53 .…”

Gene introduction approaches in chloroplast transformation and its applications

“…The stresses could be categorized into biotic and abiotic stress. Biotic stress indicates the stress was due to the plant’s vulnerability towards the biology components such as microbes and insects, while abiotic stress is indicating the exposure of the plants to a physically harsh environment such as climate change and exposure to chemicals like pesticides and herbicides [ 4 , 17 , 54 ]. These stresses need to be addressed as they affect the plants on a large scale as well as affecting the plant metabolic function and ultimately lead to the extinction of some plants due to their inability in tolerating these extrinsic stresses [ 4 , 17 , 18 , 44 , 47 , 54 ].…”

“…Transgenic plants could be the alternative solution for this issue as the production of transgenic crops that can overcome the abiotic and biotic stress could result in higher and enhanced crop production [ 54 ]. With chloroplast transformation, there are some achievements that have been reported.…”