title: Uptake, effects, and metabolism of cyanobacterial toxins in the emergent reed plant Phragmites australis (cav.) trin. ex steud.
abstract: The commonly occurring cyanobacterial toxin microcystin-LR (MC-LR) was rapidly taken up by the emergent reed plant Phragmites australis with clear distribution in the different cormus parts of the plant. Highest uptake was detected in the stem, followed by the rhizome. Enzyme extracts of the rhizome system, the stem, and the leaf revealed the presence of soluble glutathione S-transferases (sGST) measured with the model substrate 1-chloro-2,4-dinitrobenzene. A significant elevation of sGST activity in the rhizome and stem parts of P. australis was detected after a 24-h exposure to 0.5 microg/L MC-LR. Rhizome, stem, and leaf tissues were also able to conjugate several microcystin toxins. However, no conjugation, either chemical nor enzymatic, was detected using the related cyanobacterial toxin nodularin as substrate. Highest glutathione S-transferase activity for the toxin substrates was detected in the pkat/mg range in the stem of P. australis. For MC-LR, a complete metabolism from the formation of a glutathione conjugate to the degradation of a cysteine conjugate in all cormus parts of the plant is reported. The stepwise degradation of the MC-LR-glutathione conjugate to a gamma-glutamylcysteine and a cysteine conjugate was demonstrated by comparison with chemically formed reference compounds and by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. This is the first evidence for the uptake and metabolism of cyanobacterial toxins by an emergent aquatic macrophyte.
authors.affiliation: Institute of Freshwater Ecology and Inland Fisheries, Berlin, Germany. pflug@igb-berlin.de
authors.forename: S
authors.initials: S
authors.lastname: Pflugmacher
authors.forename: C
authors.initials: C
authors.lastname: Wiegand
authors.forename: K A
authors.initials: KA
authors.lastname: Beattie
authors.forename: E
authors.initials: E
authors.lastname: Krause
authors.forename: C E
authors.initials: CE
authors.lastname: Steinberg
authors.forename: G A
authors.initials: GA
authors.lastname: Codd
mesh_terms: D001427:Bacterial Toxins / Q000493:pharmacokinetics / Q000633:toxicity*; D001692:Biological Transport; D001711:Biotransformation; D002250:Carbon Radioisotopes; D002851:Chromatography, High Pressure Liquid; D000458:Cyanobacteria; D005618:Fresh Water; D005982:Glutathione Transferase / Q000378:metabolism; D007700:Kinetics; D019684:Magnoliopsida / Q000187:drug effects / Q000502:physiology*; D008387:Marine Toxins; D013058:Mass Spectrometry; D052998:Microcystins; D010456:Peptides, Cyclic / Q000493:pharmacokinetics / Q000633:toxicity*; D018515:Plant Leaves / Q000378:metabolism; D018517:Plant Roots / Q000378:metabolism; D018547:Plant Stems / Q000378:metabolism
chemical_list: D001427:Bacterial Toxins; D002250:Carbon Radioisotopes; D008387:Marine Toxins; D052998:Microcystins; D010456:Peptides, Cyclic; D005982:Glutathione Transferase; C057862:cyanoginosin LR