Evidence of a significant role of glutathione reductase in the sulfur assimilation pathway

Abstract

With the objective of studying the role of glutathione reductase (GR) in the accumulation of cysteine and methionine, we generated transgenic tobacco and Arabidopsis lines overexpressing the cytosolic AtGR1 and the plastidic AtGR2 genes. The transgenic plants had higher contents of cysteine and glutathione. To understand why cysteine levels increased in these plants, we also used gr1 and gr2 mutants. The results showed that the transgenic plants have higher levels of sulfite, cysteine, glutathione and methionine, which are downstream to adenosine 5 0 phosphosulfate reductase (APR) activity. However, the mutants had lower levels of these metabolites, while the sulfate content increased. A feeding experiment using 34 SO 4 2also showed that the levels of APR downstream metabolites increased in the transgenic lines and decreased in gr1 compared with their controls. These findings, and the results obtained from the expression levels of several genes related to the sulfur pathway, suggest that GR plays an essential role in the sulfur assimilation pathway by supporting the activity of APR, the key enzyme in this pathway. GR recycles the oxidized form of glutathione (GSSG) back to reduce glutathione (GSH), which serves as an electron donor for APR activity. The phenotypes of the transgenic plants and the mutants are not significantly altered under non-stress and oxidative stress conditions. However, when germinating on sulfur-deficient medium, the transgenic plants grew better, while the mutants were more sensitive than the control plants. The results give substantial evidence of the yet unreported function of GR in the sulfur assimilation pathway.

Identification of ascorbate‐ and salicylate‐responsive miRNAs and verification of the spectral control of miR395 in Arabidopsis

“…In addition, GSH is also a positive regulator of the second step of sulphate reduction since it serves as an electron donor for adenosine phosphosulphate reductase (APSR), the second enzyme of this pathway. GR, ensuring the regeneration of GSH from glutathione disulphide (GSSG), is involved in the control of sulphate reduction as demonstrated in transgenic and mutant Arabidopsis lines having increased and decreased levels of downstream metabolites (sulphite, cysteine and GSH), respectively (Cohen et al 2020). Far‐red light increased the expression of the genes encoding APSR, gamma‐glutamylcysteine synthetase and GR and the amount of GSH and reduced the level of GSSG compared to blue light as observed in barley (Balogh et al 2022).…”

Cysteine and Methionine Biosynthetic Enzymes Have Distinct Effects on Seed Nutritional Quality and on Molecular Phenotypes Associated With Accumulation of a Methionine-Rich Seed Storage Protein in Rice

“…Although there is no evidence of SAT regulation by phosphorylation in Arabidopsis, the chloroplast cyclophilin CYP20-3 participates in folding of AtSAT1 in a redox-dependent fashion, to enhance the activity of AtSAT1 and to affect thiol contents (Dominguez-Solis et al, 2008). Additionally, it was recently shown that the availability of (reduced) GSH in Arabidopsis and tobacco positively affects S-assimilation downstream of APR activity, including the steady state concentration of cysteine and methionine (Cohen et al, 2020). The data presented in this study support that redox regulation of sulfate assimilation and cysteine synthesis also occurs in rice.…”

A cotton APS REDUCTASE represses root hair elongation via sulfur assimilation and hydrogen peroxide‐mediated cell wall damage

“…Sulfur is an essential macronutrient very important for the growth and function of plants (Zenda et al 2021). For example, sulfur treatment can reduce the accumulation of heavy metals in plants and improve stress resistance (Cao et al 2023), and sulfur deficiency will lead to growth and yield decline (Cohen et al 2020, Narayan et al 2022, Cao et al 2023). But its role in single‐cell development (e.g., trichome cell, root hair) is unknown.…”