title: Expression of Caenorhabditis elegans PCS in the AtPCS1-deficient Arabidopsis thaliana cad1-3 mutant separates the metal tolerance and non-host resistance functions of phytochelatin synthases.
abstract: Phytochelatin synthases (PCS) play key roles in plant metal tolerance. They synthesize small metal-binding peptides, phytochelatins, under conditions of metal excess. Respective mutants are strongly cadmium and arsenic hypersensitive. However, their ubiquitous presence and constitutive expression had long suggested a more general function of PCS besides metal detoxification. Indeed, phytochelatin synthase1 from Arabidopsis thaliana (AtPCS1) was later implicated in non-host resistance. The two different physiological functions may be attributable to the two distinct catalytic activities demonstrated for AtPCS1, that is the dipeptidyl transfer onto an acceptor molecule in phytochelatin synthesis, and the proteolytic deglycylation of glutathione conjugates. In order to test this hypothesis and to possibly separate the two biological roles, we expressed a phylogenetically distant PCS from Caenorhabditis elegans in an AtPCS1 mutant. We confirmed the involvement of AtPCS1 in non-host resistance by showing that plants lacking the functional gene develop a strong cell death phenotype when inoculated with the potato pathogen Phytophthora infestans. Furthermore, we found that the C. elegans gene rescues phytochelatin synthesis and cadmium tolerance, but not the defect in non-host resistance. This strongly suggests that the second enzymatic function of AtPCS1, which remains to be defined in detail, is underlying the plant immunity function.
authors.affiliation: Department of Plant Physiology, University of Bayreuth, Universitätsstrasse 30, Bayreuth, 95440, Germany.
authors.forename: Tanja
authors.initials: T
authors.lastname: Kühnlenz
authors.affiliation: Department of Stress and Developmental Biology, Leibniz Institute of Plant Biochemistry, Weinberg 3, Halle, 06120, Germany.
authors.forename: Lore
authors.initials: L
authors.lastname: Westphal
authors.affiliation: Department of Plant Physiology, University of Bayreuth, Universitätsstrasse 30, Bayreuth, 95440, Germany.
authors.forename: Holger
authors.initials: H
authors.lastname: Schmidt
authors.affiliation: Department of Stress and Developmental Biology, Leibniz Institute of Plant Biochemistry, Weinberg 3, Halle, 06120, Germany.
authors.forename: Dierk
authors.initials: D
authors.lastname: Scheel
authors.affiliation: Department of Plant Physiology, University of Bayreuth, Universitätsstrasse 30, Bayreuth, 95440, Germany.
authors.forename: Stephan
authors.initials: S
authors.lastname: Clemens
mesh_terms: D000220:Adaptation, Biological / Q000235:genetics; D019881:Aminoacyltransferases / Q000235:genetics* / Q000502:physiology; D017360:Arabidopsis / Q000276:immunology / Q000382:microbiology / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000502:physiology; D029742:Caenorhabditis elegans Proteins / Q000235:genetics*; D016923:Cell Death / Q000235:genetics; D060467:Disease Resistance / Q000235:genetics; D009154:Mutation; D055750:Phytophthora infestans; D030821:Plants, Genetically Modified / Q000276:immunology / Q000382:microbiology / Q000502:physiology
chemical_list: D029681:Arabidopsis Proteins; D029742:Caenorhabditis elegans Proteins; D019881:Aminoacyltransferases; C502365:AT5G44070 protein, Arabidopsis; C548905:phytochelatin synthase, C elegans
keywords: cadmium; innate immunity; metal homeostasis; non-host resistance; phytochelatins; plant defence