title: Microcystin-LR induces mitotic spindle assembly disorders in Vicia faba by protein phosphatase inhibition and not reactive oxygen species induction.
abstract: We aimed to reveal the mechanisms of mitotic spindle anomalies induced by microcystin-LR (MCY-LR), a cyanobacterial toxin in Vicia faba, a well-known model in plant cell and molecular biology. MCY-LR inhibits type 1 and 2A phosphoserine/threonine specific protein phosphatases (PP1 and PP2A) and induces reactive oxygen species (ROS) formation. The cytoskeleton is one of the main targets of the cyanotoxin during cytopathogenesis. Histochemical-immunohistochemical and biochemical methods were used. A significant number of MCY-LR induced spindle alterations are described for the first time. Disrupted, multipolar spindles and missing kinetochore fibers were detected both in metaphase and anaphase cells. Additional polar microtubule (MT) bundles, hyperbundling of spindle MTs, monopolar spindles, C-S- shaped, additional and asymmetric spindles were detected in metaphase, while midplane kinetochore fibers were detected in anaphase cells only. Several spindle anomalies induced mitotic disorders, i.e. they occurred concomitantly with altered sister chromatid separation. Alterations were dependent on the MCY-LR dose and exposure time. Under long-term (2 and mainly 6 days') exposure they were detected in the concentration range of 0.1-20μgmL(-1) MCY-LR that inhibited PP1 and PP2A significantly without significant ROS induction. Elevated peroxidase/catalase activities indicated that MCY-LR treated V. faba plants showed efficient defense against oxidative stress. Thus, although the elevation of ROS is known to induce cytoskeletal aberrations in general, this study shows that long-term protein phosphatase inhibition is the primary cause of MCY-LR induced spindle disorders.
authors.affiliation: Department of Botany, Faculty of Science and Technology, University of Debrecen, Egyetem ter 1, H-4032, Debrecen, Hungary. Electronic address: gtamas0516@gmail.com.
authors.forename: Tamás
authors.initials: T
authors.lastname: Garda
authors.affiliation: Department of Botany, Faculty of Science and Technology, University of Debrecen, Egyetem ter 1, H-4032, Debrecen, Hungary. Electronic address: konya.zoltan@med.unideb.hu.
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Kónya
authors.affiliation: Department of Botany, Faculty of Science and Technology, University of Debrecen, Egyetem ter 1, H-4032, Debrecen, Hungary. Electronic address: dike15ster@gmail.com.
authors.forename: Ildikó
authors.initials: I
authors.lastname: Tándor
authors.affiliation: Department of Botany, Faculty of Science and Technology, University of Debrecen, Egyetem ter 1, H-4032, Debrecen, Hungary. Electronic address: beyerdani@gmail.com.
authors.forename: Dániel
authors.initials: D
authors.lastname: Beyer
authors.affiliation: Department of Botany, Faculty of Science and Technology, University of Debrecen, Egyetem ter 1, H-4032, Debrecen, Hungary. Electronic address: vasas.gabor@science.unideb.hu.
authors.forename: Gábor
authors.initials: G
authors.lastname: Vasas
authors.affiliation: Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, Egyetem ter 1, H-4032, Debrecen, Hungary. Electronic address: erdodi@med.unideb.hu.
authors.forename: Ferenc
authors.initials: F
authors.lastname: Erdődi
authors.affiliation: Department of Biophysics and Cell Biology, Faculty of Medicine, University of Debrecen, Egyetem ter 1, H-4032, Debrecen, Hungary. Electronic address: vereb@med.unideb.hu.
authors.forename: György
authors.initials: G
authors.lastname: Vereb
authors.affiliation: Department of Botany, Faculty of Science and Technology, University of Debrecen, Egyetem ter 1, H-4032, Debrecen, Hungary. Electronic address: papp.georgina93@gmail.com.
authors.forename: Georgina
authors.initials: G
authors.lastname: Papp
authors.affiliation: Department of Botany, Faculty of Science and Technology, University of Debrecen, Egyetem ter 1, H-4032, Debrecen, Hungary. Electronic address: ribamilan@freemail.hu.
authors.forename: Milán
authors.initials: M
authors.lastname: Riba
authors.affiliation: Department of Botany, Faculty of Science and Technology, University of Debrecen, Egyetem ter 1, H-4032, Debrecen, Hungary. Electronic address: hamvas.marta@science.unideb.hu.
authors.forename: Márta
authors.initials: M
authors.lastname: M-Hamvas
authors.affiliation: Department of Botany, Faculty of Science and Technology, University of Debrecen, Egyetem ter 1, H-4032, Debrecen, Hungary. Electronic address: mathe.csaba@science.unideb.hu.
authors.forename: Csaba
authors.initials: C
authors.lastname: Máthé
mesh_terms: D000705:Anaphase / Q000187:drug effects; D000975:Antioxidants / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D008387:Marine Toxins; D018519:Meristem / Q000187:drug effects / Q000378:metabolism; D008677:Metaphase / Q000187:drug effects; D052998:Microcystins / Q000494:pharmacology*; D018384:Oxidative Stress / Q000187:drug effects; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D008941:Spindle Apparatus / Q000187:drug effects / Q000378:metabolism*; D013997:Time Factors; D031307:Vicia faba / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*
chemical_list: D000975:Antioxidants; D004791:Enzyme Inhibitors; D008387:Marine Toxins; D052998:Microcystins; D017382:Reactive Oxygen Species; D010749:Phosphoprotein Phosphatases; C057862:cyanoginosin LR
keywords: Microcystin-LR; Protein phosphatase; Reactive oxygen species; Spindle alteration; Vicia faba