Independent roles of glutathione and O-acetyl-L-serine in regulation of sulfur-responsive gene expression in Arabidopsis thaliana

Abstract

We investigated the effects of a four-day treatment with 0.3 mM glutathione (GSH) and 10 mM O-acetyl-Lserine (OAS), negative and positive regulators of sulfur-responsive gene expression, respectively, alone or in combination, on the sulfur-responsive gene expression in ten-day-old Arabidopsis thaliana plants. We determined the relationship between the concentrations of GSH, OAS and sulfate, and expression of sulfur-responsive genes in rosette leaves. The concentrations of GSH and OAS correlated negatively and positively with expression of genes, respectively, suggesting that GSH and OAS independently affect expression of sulfur-responsive genes. A simple scheme of sulfur assimilation pathway from sulfate to glutathione. Sulfate in the environment is taken up and reduced to form cysteine (Cys). O-acetyl-L-serine (OAS) is synthesized from the N assimilation pathway and conjugate with reduced sulfur to form Cys. Glutathione (GSH) is synthesized from Cys and the synthesis is inhibited by buthionine sulfoximine (BSO). OAS and GSH have been shown to affect expression of sulfur-responsive genes.We examined the effects of exogenous application of GSH and OAS on the expression of sulfur-responsive genes or elements, b SR , Sultr2;2, APR1, and SAT1 in NOB7 plants. There was no significant difference in expression patterns of Sultr2;2, APR1, and SAT1 between the NOB7 plants and Col-0 wild-type plants in any of the following experiments (data not shown). Plants were initially grown on agarose plates containing 1,500 mM sulfate for ten days. Then they were cultured for four days on fresh agarose plates containing 1,500 mM or 1.5 mM sulfate with or without 0.3 mM GSH, 10 mM OAS or 1 mM BSO alone or in combination (Table 1). The media used in the present study were as described previously (Hirai et al. 1995). OAS, GSH and BSO were filter-sterilized and added after autoclaving the media to avoid possible degradation during autoclaving. To avoid any changes in pH in the media by addition of these reagents, we dissolved OAS, GSH and BSO in a small volume of media and readjusted the pH prior to filter sterilization.After the treatment, we collected the rosette leaves of the plants and determined the concentrations of GSH, OAS and sulfate, referred to hereafter as [GSH] (Table 2), and levels of GFP fluorescence, and accumulation of mRNA for Sultr2;2, APR1, and SAT1 (Table 3). For the quantification of GFP, we used relative GFP fluorescence (Table 3), which represents the intensity of fluorescence corresponding to GFP in NOB7 plants relative to chlorophyll autofluorescence as described by Niwa et al. (1999). The relative levels of Sultr2;2, APR1 or SAT1 transcript accumulation to that of b-tubulin transcript were caluculated (Table 3) (Table 2, compare C and CG). These results suggest that the negative effect of GSH on the expression of sulfur-responsive genes was not evident in plants grown with normal levels of sulfate. In these plants, [GSH] GSH, OAS and BSO were applied at the initial concentrations of 0.3, 10, and...

Glutathione degradation activity of γ‐glutamyl peptidase 1 manifests its dual roles in primary and secondary sulfur metabolism in Arabidopsis

“…Instead, it is more likely that this OAS accumulation was caused by perturbed GSH degradation, considering that the ggct2;1 mutant similarly showed higher OAS levels under sulfur deficiency. Although the expression levels of OAS-responsive genes such as APR3, SDI1, and GGCT2;1 (Aarabi et al, 2020;Watanabe et al, 2021) were not significantly affected by this OAS accumulation (Figure 5a), this can be well explained according to the report by Sogawa et al (2005). They reported that additional OAS application does not induce sulfur-responsive gene expression when plants are already exposed to sulfur deficiency, and also found that GSH negatively regulates sulfur-responsive gene expression.…”

Transcriptomic and Metabolomics Analysis of Different Endosperm Region under Nitrogen Treatments

“…A close relationship between amino acid transporters and GSP content has been reported in wheat and barley [23,33]. Clearly, the increased amino acid content in the innermost endosperm region might function in other regulatory mechanisms related to storage protein deposition, because it has been shown that amino acid precursors, such as O-aceylserine, regulate the GSP content [29,34].…”

Transcriptional and metabolic alternations rebalance wheat grain storage protein accumulation under variable nitrogen and sulfur supply

“…O –acetylserine) or small peptides (e.g. GSH) also serve as signals in the regulation of grain N and S allocation to GSP (Sogawa et al ., ; Ohkama‐Ohtsu et al ., ). We observed coordinated changes between N, S and C metabolisms and GSP accumulation.…”