ZINC TOLERANCE INDUCED BY IRON 1 reveals the importance of glutathione in the cross‐homeostasis between zinc and iron in Arabidopsis thaliana

Abstract

SUMMARYZinc is an essential micronutrient for plants, but it is toxic in excess concentrations. In Arabidopsis, additional iron (Fe) can increase Zn tolerance. We isolated a mutant, zinc tolerance induced by iron 1, designated zir1, with a defect in Fe-mediated Zn tolerance. Using map-based cloning and genetic complementation, we identified that zir1 has a mutation of glutamate to lysine at position 385 on c-glutamylcysteine synthetase (GSH1), the enzyme involved in glutathione biosynthesis. The zir1 mutant contains only 15% of the wild-type glutathione level. Blocking glutathione biosynthesis in wild-type plants by a specific inhibitor of GSH1, buthionine sulfoximine, resulted in loss of Fe-mediated Zn tolerance, which provides further evidence that glutathione plays an essential role in Fe-mediated Zn tolerance. Two glutathione-deficient mutant alleles of GSH1, pad2-1 and cad2-1, which contain 22% and 39%, respectively, of the wild-type glutathione level, revealed that a minimal glutathione level between 22 and 39% of the wild-type level is required for Fe-mediated Zn tolerance. Under excess Zn and Fe, the recovery of shoot Fe contents in pad2-1 and cad2-1 was lower than that of the wild type. However, the phytochelatin-deficient mutant cad1-3 showed normal Fe-mediated Zn tolerance. These results indicate a specific role of glutathione in Fe-mediated Zn tolerance. The induced accumulation of glutathione in response to excess Zn and Fe suggests that glutathione plays a specific role in Fe-mediated Zn tolerance in Arabidopsis. We conclude that glutathione is required for the cross-homeostasis between Zn and Fe in Arabidopsis.

Heavy Metals Induce Iron Deficiency Responses at Different Hierarchic and Regulatory Levels

“…S3; Fukao et al, 2011), which, in principle, would be sufficient to explain the subsequent induction of Fe deficiency-related processes. As reported previously (Fukao et al, 2011;Shanmugam et al, 2011Shanmugam et al, , 2012, foliar Fe supply strongly suppressed the development of chlorosis upon excess Zn (Fig. 6, A and B) and reduced shoot Zn accumulation to a certain extent (Supplemental Fig.…”

Detoxification strategies and regulation of oxygen production and flowering of Platanus acerifolia under lead (Pb) stress by transcriptome analysis

“…In Arabidopsis thaliana, increased GSH levels were found to fortify oxidation tolerance to cadmium-and iron-mediated zinc stress (Maksymiec et al 2007;Shanmugam et al 2012;Sobrino-Plata et al 2014). It has been suggested that the activities of several antioxidant enzymes (GR and CAT) may be influenced by the transition between GSH and glutathione disulfide (GSSG) (Seth et al 2012).…”

Glutamate Receptor-Like Channel3.3 Is Involved in Mediating Glutathione-Triggered Cytosolic Calcium Transients, Transcriptional Changes, and Innate Immunity Responses in Arabidopsis

“…Arabidopsis (Arabidopsis thaliana) knockout mutants completely deficit in GSH biosynthesis show either embryo-or seedling-lethal phenotypes (Cairns et al, 2006;Pasternak et al, 2008), demonstrating its indispensable role in plant development. Other Arabidopsis mutants that have various degrees of reduction in endogenous GSH content show altered expression of stress-related genes (Ball et al, 2004;Mhamdi et al, 2010;Han et al, 2013aHan et al, , 2013b, enhancing sensitivity to excessive zinc (Shanmugam et al, 2012) and cadmium (Jozefczak et al, 2012) as well as pathogens (Parisy et al, 2007;Dubreuil-Maurizi and Poinssot, 2012).…”