Microcystin-LR induces abnormal root development by altering microtubule organization in tissue-cultured common reed (Phragmites australis) plantlets.
Microcystin-LR (MC-LR) is a heptapeptide cyanotoxin, known to be a potent inhibitor of type 1 and 2A protein phosphatases in eukaryotes. Our aim was to investigate the effect of MC-LR on the organization of microtubules and mitotic chromatin in relation to its possible effects on cell and whole organ morphology in roots of common reed (Phragmites australis). P. australis is a widespread freshwater and brackish water aquatic macrophyte, frequently exposed to phytotoxins in eutrophic waters. Reed plantlets regenerated from embryogenic calli were treated with 0.001-40 microg ml(-1) (0.001-40.2 microM) MC-LR for 2-20 days. At 0.5 microg ml(-1) MC-LR and at higher cyanotoxin concentrations, the inhibition of protein phosphatase activity by MC-LR induced alterations in reed root growth and morphology, including abnormal lateral root development and the radial swelling of cells in the elongation zone of primary and lateral roots. Both short-term (2-5 days) and long-term (10-20 days) of cyanotoxin treatment induced microtubule disruption in meristems and in the elongation and differentiation zones. Microtubule disruption was accompanied by root cell shape alteration. At concentrations of 0.5-5 microg ml(-1), MC-LR increased mitotic index at long-term exposure and induced the increase of the percentage of meristematic cells in prophase as well as telophase and cytokinesis of late mitosis. High cyanotoxin concentrations (10-40 microg ml(-1)) inhibited mitosis at as short as 2 days of exposure. The alteration of microtubule organization was observed in mitotic cells at all exposure periods studied, at cyanotoxin concentrations of 0.5-40 microg ml(-1). MC-LR induced spindle anomalies at the metaphase-anaphase transition, the formation of asymmetric anaphase spindles and abnormal sister chromatid separation. This paper reports for the first time that MC-LR induces cytoskeletal changes that lead to alterations of root architecture and development in common reed and generally, in plant cells. The MC-LR induced alterations in cells of an ecologically important aquatic macrophyte can reveal the importance of the effects of a cyanobacterial toxin in aquatic ecosystems.
Máthé
Csaba
C
University of Debrecen, Department of Botany, Faculty of Science and Technology, PO Box 14, H-4010 Debrecen, Hungary. mathe@tigris.unideb.hu
Beyer
Dániel
D
Erdodi
Ferenc
F
Serfozo
Zoltán
Z
Székvölgyi
Lóránt
L
Vasas
Gábor
G
M-Hamvas
Márta
M
Jámbrik
Katalin
K
Gonda
Sándor
S
Kiss
Andrea
A
Szigeti
Zsuzsa M
ZM
Surányi
Gyula
G
D007399:Interphase / Q000187:drug effects; D008387:Marine Toxins; D018519:Meristem / Q000187:drug effects; D052998:Microcystins / Q000633:toxicity*; D008870:Microtubules / Q000187:drug effects*; D008938:Mitosis / Q000187:drug effects; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects* / Q000254:growth & development; D006109:Poaceae / Q000187:drug effects* / Q000201:enzymology; D046509:Tissue Culture Techniques; D014874:Water Pollutants, Chemical / Q000633:toxicity*
D008387:Marine Toxins; D052998:Microcystins; D014874:Water Pollutants, Chemical; D010749:Phosphoprotein Phosphatases; C057862:cyanoginosin LR