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 with 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.

中文翻译：

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谷胱甘肽转移酶 U7 在植物生长和保护免受甲基紫精诱导的氧化应激中的双重作用

植物谷胱甘肽 S-转移酶 (GSTs) 是具有多种功能的谷胱甘肽依赖性酶，主要与亲电子异生物质和过氧化物的解毒有关。拟南芥 (Arabidopsis thaliana) 基因组编码 53 个 GST，分为 7 个亚类；但是，对其精确功能的理解是有限的。最近的一项研究表明，II 类 TGA 转录因子 TGA2、TGA5 和 TGA6 对于耐受 UV-B 诱导的氧化应激至关重要，并且这种耐受性与细胞溶质 tau-GST (GSTU) 的抗氧化功能有关。具体而言，TGA2 控制 UV-B 光下几个 GSTU 的表达，并且 tga256 三重突变体中 GSTU7 的组成型表达足以恢复 tga256 的 UV-B 易感表型。为了进一步研究GSTU7的功能，我们描述了它在减轻除草剂甲基紫精（MV）引起的氧化损伤中的作用。在非胁迫条件下，gstu7 无效突变体比野生型 (WT) 植物小，并且延迟了 MV 诱导的抗氧化反应的发生，这导致过氧化氢的积累和幼苗存活率降低。通过 GSTU7 的组成型表达对 gstu7 的互补挽救了这些表型。此外，用荧光探针 Grx1-roGFP2 实时监测完整细胞中的谷胱甘肽氧化还原电位显示，与 WT 植物相比，GSTU7 过表达完全消除了 MV 诱导的细胞溶质谷胱甘肽缓冲液的氧化。GSTU7 充当谷胱甘肽过氧化物酶，能够补充酵母中过氧化物酶型 GST 的缺乏。一起，