A dual role for glutathione transferase U7 in plant growth and protection from methyl viologen-induced oxidative stress

Abstract

Plant glutathione S-transferases (GSTs) are glutathione-dependent enzymes with versatile functions, mainly related to detoxification of electrophilic xenobiotics and peroxides. The Arabidopsis (Arabidopsis thaliana) genome codes for 53 GSTs, divided into seven subclasses, however, understanding of their precise functions is limited. A recent study showed that class II TGA transcription factors TGA2, TGA5 and TGA6 are essential for tolerance of UV-B-induced oxidative stress and that this tolerance is associated with an antioxidative function of cytosolic tau-GSTs (GSTUs). Specifically, TGA2 controls the expression of several GSTUs under UV-B light, and constitutive expression of GSTU7 in the tga256 triple mutant is sufficient to revert the UV-B-susceptible phenotype of tga256. To further study the function of GSTU7, we characterized its role in mitigation of oxidative damage caused by the herbicide methyl viologen (MV). Under non-stress conditions, gstu7 null mutants were smaller than wild-type (WT) plants and delayed in the onset of the MV-induced antioxidative response, which led to accumulation of hydrogen peroxide and diminished seedling survival. Complementation of gstu7 by constitutive expression of GSTU7 rescued these phenotypes. Furthermore, live monitoring of the glutathione redox potential in intact cells with the fluorescent probe Grx1-roGFP2 revealed that GSTU7 overexpression completely abolished the MV-induced oxidation of the cytosolic glutathione buffer compared to WT plants. GSTU7 acted as a glutathione peroxidase able to complement the lack of peroxidase-type GSTs in yeast. Together, these findings show that GSTU7 is crucial in the antioxidative response by limiting oxidative damage and thus contributes to oxidative stress resistance in the cell.

The Glutathione S-Transferase PtGSTF1 Improves Biomass Production and Salt Tolerance through Regulating Xylem Cell Proliferation, Ion Homeostasis and Reactive Oxygen Species Scavenging in Poplar

“…PtGSTF1 was abundantly expressed in leaves and was responsive to high salt stress ( Figure 1 b,c). This is similar to the expression patterns of other previously reported GST members, which showed induced expression by various biotic and abiotic stresses in different biological metabolism processes [ 16 , 31 , 33 , 34 , 44 , 45 ]. In Arabidopsis, GSTU7 was reported to be localized in the cytosol, whereas the tea CsGSTU8 was found to be distributed throughout the cell [ 16 , 17 , 46 , 47 ].…”

“…This is similar to the expression patterns of other previously reported GST members, which showed induced expression by various biotic and abiotic stresses in different biological metabolism processes [ 16 , 31 , 33 , 34 , 44 , 45 ]. In Arabidopsis, GSTU7 was reported to be localized in the cytosol, whereas the tea CsGSTU8 was found to be distributed throughout the cell [ 16 , 17 , 46 , 47 ]. We observed that PtGSTF1 was located in the cytoplasm, implying that it may have a similar role to the GSTU7 protein ( Figure 1 c).…”

“…The first plant GSTs were reported in sorghum and maize, and catalyzed the detoxification of the herbicide atrazine by conjugating to the endogenous tripeptide glutathione (GSH, γ-L-glutamyl-L-cysteinyl-glycine) [ 10 ]. Since then, a number of studies focused on the detoxification function of glutathione transferase to herbicides in plants have been carried out [ 11 , 12 , 13 , 14 , 15 , 16 ]. Plant GSTs were also found to be involved in other processes such as plant development and secondary metabolism [ 17 , 18 ].…”

“…The induction of GSTs strongly reinforces their protective role against oxidative stress across this extensive span of treatments [ 26 ]. Apart from this, GSTs are also induced by phytohormones such as auxin, salicylic acid (SA), abscisic acid (ABA), ethylene, and other hormones, which implies that plant GSTs play dynamic roles in plant growth and development [ 16 , 27 , 28 ]. Increasingly, evidence has demonstrated that unique combinations of multiple signaling pathways from various phytohormones and reactive oxygen species or antioxidants rendered distinct transcriptional activation patterns of individual GSTs during various stresses.…”

“…RT-PCR analyses showed that the expression of AtGSTU17 was regulated by various photoreceptors, especially phytochrome A (phyA) and different plant hormones, such as auxin and ABA, under all light conditions [ 31 ]. Similarly, GSTU7 was induced by a variety of stress stimuli and played a role not only in the growth of Arabidopsis but also in the protective response for cellular detoxification to herbicides [ 16 ]. In Chinese cabbage, the BcGSTU gene promoted growth, development and stress tolerance in transgenic Arabidopsis [ 32 ].…”