Recruitment of glutathione into the nucleus during cell proliferation adjusts whole-cell redox homeostasis in Arabidopsis thaliana and lowers the oxidative defence shield

Abstract

SUMMARYCellular redox homeostasis and signalling are important in progression of the eukaryotic cell cycle. In animals, the low-molecular-weight thiol tripeptide glutathione (GSH) is recruited into the nucleus early in the cell proliferation cycle. To determine whether a similar process occurs in plants, we studied cell proliferation in Arabidopsis thaliana. We show that GSH co-localizes with nuclear DNA during the proliferation of A. thaliana cells in culture. Moreover, GSH localization in the nucleus was observed in dividing pericycle cells of the lateral root meristem. There was pronounced accumulation of GSH in the nucleus at points in the growth cycle at which a high percentage of the cells were in G 1 phase, as identified by flow cytometry and marker transcripts. Recruitment of GSH into the nucleus led to a high abundance of GSH in the nucleus (GSHn) and severe depletion of the cytoplasmic GSH pool (GSHc). Sequestration of GSH in the nucleus was accompanied by significant decreases in transcripts associated with oxidative signalling and stress tolerance, and an increase in the abundance of hydrogen peroxide, an effect that was enhanced when the dividing cells were treated with salicylic acid. Total cellular GSH and the abundance of GSH1 and GSH2 transcripts increased after the initial recruitment of GSH into the nucleus. We conclude that GSH recruitment into the nucleus during cell proliferation has a profound effect on the whole-cell redox state. High GSHn levels trigger redox adjustments in the cytoplasm, favouring decreased oxidative signalling and enhanced GSH synthesis.

Glutathione – linking cell proliferation to oxidative stress

“…Data such as that shown in Figure 4 demonstrates that the nuclear GSH pool is in equilibrium with that of the cytosol. However, studies on animal and plant cells have demonstrated GSH is compartmentalized in the nucleus during the cell cycle (5)(6)(7)(8)107).…”

“…GSH co-localizes with nuclear DNA during cell proliferation in animals (8) and plants (5,6,96,107). In such studies, the nuclear GSH pool has been monitored largely by cconfocal microscopy using a double staining procedure involving Hoechst 33342 (Hoechst; blue stain) to localize nuclear DNA and CellTracker green 5-chloromethylfluorescein diacetate (CMFDA; green stain) to detect GSH (5,6,86,107).…”

“…Like other small molecules, GSH diffuses freely between the cytosol and nucleus through the nuclear pore complex (4). It is rather surprising therefore that the nuclear GSH pool is much more resistant to depletion than the cytosolic pool, a property that is particularly important during cell proliferation (5)(6)(7)(8). Although relatively little is known about the nuclear thioredoxins (TRX) and glutaredoxins (GRXs) or their functions in plants (9) it is probable that these redox proteins participate in the plethora of thiol-dependent redox regulation mechanisms and post-translational modifications that are required for plant growth and development, particularly through functions in the nuclei.The many important roles of glutathione in plants have been well documented in recent reviews (1,2,10) and hence the following discussion will focus on how GSH functions as a regulator of plant development, with a particular focus on the nuclear GSH and the regulation of mitosis.…”

Defects in a New Class of Sulfate/Anion Transporter Link Sulfur Acclimation Responses to Intracellular Glutathione Levels and Cell Cycle Control

“…Additionally, glutathione has been shown to play a role in cell cycle progression in plants and animals (Thelander and Reichard, 1979;Menon et al, 2003;Menon and Goswami, 2007;Diaz Vivancos et al, 2010b). Therefore, we speculated that SMT15 might connect sulfur acclimation to cell cycle control through the misregulation of glutathione homeostasis.…”

“…Our finding that glutathione overaccumulates in smt15-1 but not in sac mutants is a possible clue for understanding the cell cycle defects in this mutant. Glutathione levels and subcellular localization have been linked to cell cycle control in both plants and animals (Markovic et al, 2007;Pallardó et al, 2009;Pellny et al, 2009;Diaz Vivancos et al, 2010a, 2010b, although its specific impact on cell cycle-related processes is not completely understood. Changing the redox state of cell cycle regulators through glutathionylation has also been shown to influence the cell cycle (Chiu and Dawes, 2012).…”