title: ZINC TOLERANCE INDUCED BY IRON 1 reveals the importance of glutathione in the cross-homeostasis between zinc and iron in Arabidopsis thaliana.
abstract: Zinc 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 γ-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.
authors: Molecular and Biological Agricultural Sciences, Taiwan International Graduate Program, National Chung-Hsing University and Academia Sinica, Taipei, Taiwan.
authors: Varanavasiappan
authors: V
authors: Shanmugam
authors: Munkhtsetseg
authors: M
authors: Tsednee
authors: Kuo-Chen
authors: KC
authors: Yeh
mesh_terms: D000222:Adaptation, Physiological; D000483:Alleles; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D019328:Buthionine Sulfoximine / Q000494:pharmacology; D032461:Chromosomes, Plant / Q000235:genetics / Q000378:metabolism; D003001:Cloning, Molecular; D004789:Enzyme Activation; D005816:Genetic Complementation Test; D005721:Glutamate-Cysteine Ligase / Q000235:genetics / Q000378:metabolism*; D005978:Glutathione / Q000037:antagonists & inhibitors / Q000096:biosynthesis*; D006706:Homeostasis; D007501:Iron / Q000378:metabolism* / Q000494:pharmacology; D010641:Phenotype; D054811:Phytochelatins / Q000235:genetics / Q000378:metabolism; D018520:Plant Shoots / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D017354:Point Mutation; D013438:Sulfhydryl Compounds / Q000378:metabolism; D015032:Zinc / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D029681:Arabidopsis Proteins; D013438:Sulfhydryl Compounds; D019328:Buthionine Sulfoximine; D054811:Phytochelatins; D007501:Iron; D005721:Glutamate-Cysteine Ligase; C493655:Gsh1 protein, Arabidopsis; D005978:Glutathione; D015032:Zinc