title: In vivo influence of cyanobacterial toxins on enzyme activity and gene expression of protein phosphatases in Alfalfa (Medicago sativa).
abstract: Irrigation of crop plants with surface water can be a threat if cyanobacterial toxins are present in the water. Cyanotoxins are known to cause adverse effects in plants. Microcystin (MC), a cyclic heptapeptide, with more than 70 structural variants, is a frequently occurring toxin. MC is a specific inhibitor of serine/threonine protein phosphatases 1 and 2A (PP1 and 2A), important regulatory enzymes in eukaryotic cells. Protein phosphatases consist of a catalytic subunit and one or more regulatory subunits. In Alfalfa several isoforms of the catalytic subunit of PP1 (MsPP1alpha, MsPP1beta, MsPP1gamma, MsPP1delta, MsPP1varepsilon) and PP2A (MsPP2A Calpha/beta/gamma) are known along with isoforms of the regulatory subunits of PP2A (MsPP2A Aalpha/beta, MsPP2A Balpha/beta). The in vivo effect of environmentally relevant concentrations of cyanobacterial components on the mRNA transcript level of the subunits of protein phosphatases 1 and 2A in Alfalfa (Medicago sativa) was examined using semi-quantitative RT-PCR. Plants were exposed for one week to 5 microg L(-1) microcystin-LR, microcystin-LW, okadaic acid and to cell-free cyanobacterial crude extracts from Microcystis aeruginosa containing 5 microg L(-1) microcystin-LR and a toxin-free crude extract from Synechocystis spp. The protein phosphatase activity in vivo was inhibited when exposed to toxins and crude extract containing microcystin-LR, no change was induced by Synechocystis crude extract. The gene expression of the MsPP1gamma subunit and the MsPP1varepsilon subunit was induced in plants exposed to MC-LW.
authors.affiliation: Leibniz Institute of Freshwater Ecology and Inland Fisheries, RG Biochemical Regulation, Müggelseedamm 301, 12587 Berlin, Germany.
authors.forename: Anja
authors.initials: A
authors.lastname: Peuthert
authors.forename: Linda
authors.initials: L
authors.lastname: Lawton
authors.forename: Stephan
authors.initials: S
authors.lastname: Pflugmacher
mesh_terms: D001427:Bacterial Toxins / Q000633:toxicity*; D000087522:Cyanobacteria Toxins; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D008387:Marine Toxins / Q000633:toxicity*; D000455:Medicago sativa / Q000187:drug effects* / Q000201:enzymology; D052998:Microcystins / Q000633:toxicity*; D019319:Okadaic Acid / Q000633:toxicity; D054645:Protein Phosphatase 1 / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D054648:Protein Phosphatase 2 / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism
chemical_list: D001427:Bacterial Toxins; D000087522:Cyanobacteria Toxins; D008387:Marine Toxins; D052998:Microcystins; D019319:Okadaic Acid; D054645:Protein Phosphatase 1; D054648:Protein Phosphatase 2; C057862:cyanoginosin LR