title: Earthworms produce phytochelatins in response to arsenic.
abstract: Phytochelatins are small cysteine-rich non-ribosomal peptides that chelate soft metal and metalloid ions, such as cadmium and arsenic. They are widely produced by plants and microbes; phytochelatin synthase genes are also present in animal species from several different phyla, but there is still little known about whether these genes are functional in animals, and if so, whether they are metal-responsive. We analysed phytochelatin production by direct chemical analysis in Lumbricus rubellus earthworms exposed to arsenic for a 28 day period, and found that arsenic clearly induced phytochelatin production in a dose-dependent manner. It was necessary to measure the phytochelatin metabolite concentrations directly, as there was no upregulation of phytochelatin synthase gene expression after 28 days: phytochelatin synthesis appears not to be transcriptionally regulated in animals. A further untargetted metabolomic analysis also found changes in metabolites associated with the transsulfuration pathway, which channels sulfur flux from methionine for phytochelatin synthesis. There was no evidence of biological transformation of arsenic (e.g. into methylated species) as a result of laboratory arsenic exposure. Finally, we compared wild populations of earthworms sampled from the field, and found that both arsenic-contaminated and cadmium-contaminated mine site worms had elevated phytochelatin concentrations.
authors.affiliation: Department of Surgery and Cancer, Imperial College London, London, United Kingdom.
authors.forename: Manuel
authors.initials: M
authors.lastname: Liebeke
authors.forename: Isabel
authors.initials: I
authors.lastname: Garcia-Perez
authors.forename: Craig J
authors.initials: CJ
authors.lastname: Anderson
authors.forename: Alan J
authors.initials: AJ
authors.lastname: Lawlor
authors.forename: Mark H
authors.initials: MH
authors.lastname: Bennett
authors.forename: Ceri A
authors.initials: CA
authors.lastname: Morris
authors.forename: Peter
authors.initials: P
authors.lastname: Kille
authors.forename: Claus
authors.initials: C
authors.lastname: Svendsen
authors.forename: David J
authors.initials: DJ
authors.lastname: Spurgeon
authors.forename: Jacob G
authors.initials: JG
authors.lastname: Bundy
mesh_terms: D000595:Amino Acid Sequence; D019881:Aminoacyltransferases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D000818:Animals; D001151:Arsenic / Q000494:pharmacology*; D004781:Environmental Exposure; D005786:Gene Expression Regulation / Q000187:drug effects; D053858:Metabolic Networks and Pathways / Q000187:drug effects; D055432:Metabolomics; D008969:Molecular Sequence Data; D009835:Oligochaeta / Q000145:classification / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D054811:Phytochelatins / Q000096:biosynthesis* / Q000737:chemistry; D016415:Sequence Alignment
chemical_list: D054811:Phytochelatins; D019881:Aminoacyltransferases; C093784:glutathione gamma-glutamylcysteinyltransferase; D001151:Arsenic