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Dimitris Pappas
Department of Botany, School of Biology, Aristotle University of Thessaloniki, 541 24 Thessaloniki, Greece

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Journal article
Published: 30 January 2021 in International Journal of Molecular Sciences
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Cytokinesis is accomplished in higher plants by the phragmoplast, creating and conducting the cell plate to separate daughter nuclei by a new cell wall. The microtubule-severing enzyme p60-katanin plays an important role in the centrifugal expansion and timely disappearance of phragmoplast microtubules. Consequently, aberrant structure and delayed expansion rate of the phragmoplast have been reported to occur in p60-katanin mutants. Here, the consequences of p60-katanin malfunction in cell plate/daughter wall formation were investigated by transmission electron microscopy (TEM), in root cells of the fra2 Arabidopsis thaliana loss-of-function mutant. In addition, deviations in the chemical composition of cell plate/new cell wall were identified by immunolabeling and confocal microscopy. It was found that, apart from defective phragmoplast microtubule organization, cell plates/new cell walls also appeared faulty in structure, being unevenly thick and perforated by large gaps. In addition, demethylesterified homogalacturonans were prematurely present in fra2 cell plates, while callose content was significantly lower than in the wild type. Furthermore, KNOLLE syntaxin disappeared from newly formed cell walls in fra2 earlier than in the wild type. Taken together, these observations indicate that delayed cytokinesis, due to faulty phragmoplast organization and expansion, results in a loss of synchronization between cell plate growth and its chemical maturation.

ACS Style

Emmanuel Panteris; Anna Kouskouveli; Dimitris Pappas; Ioannis-Dimosthenis Adamakis. Cytokinesis in fra2 Arabidopsis thaliana p60-katanin Mutant: Defects in Cell Plate/Daughter Wall Formation. International Journal of Molecular Sciences 2021, 22, 1405 .

AMA Style

Emmanuel Panteris, Anna Kouskouveli, Dimitris Pappas, Ioannis-Dimosthenis Adamakis. Cytokinesis in fra2 Arabidopsis thaliana p60-katanin Mutant: Defects in Cell Plate/Daughter Wall Formation. International Journal of Molecular Sciences. 2021; 22 (3):1405.

Chicago/Turabian Style

Emmanuel Panteris; Anna Kouskouveli; Dimitris Pappas; Ioannis-Dimosthenis Adamakis. 2021. "Cytokinesis in fra2 Arabidopsis thaliana p60-katanin Mutant: Defects in Cell Plate/Daughter Wall Formation." International Journal of Molecular Sciences 22, no. 3: 1405.

Preprint
Published: 12 January 2021
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Cytokinesis is accomplished in higher plants by the phragmoplast, creating and conducting the cell plate, to separate daughter nuclei by a new cell wall. The microtubule-severing enzyme p60-katanin plays an important role in the centrifugal expansion and timely disappearance of phragmoplast microtubules. Consequently, aberrant structure and delayed expansion rate of the phragmoplast occur in p60-katanin mutants. Here, the consequences of p60-katanin malfunction in cell plate/daughter wall formation were investigated by transmission electron microscopy (TEM), while deviations in the chemical composition of cell plate/new cell wall were identified by immunolabeling and confocal microscopy, in root cells of the fra2 Arabidopsis thaliana mutant. It was found that, apart from defective phragmoplast microtubule organization, cell plates/new cell walls appeared also faulty in structure, being unevenly thick and perforated by large gaps. In addition, demethylesterified homogalacturonans were prematurely present in fra2 cell plates, while callose content was significantly lower than in the wild-type. Furthermore, KNOLLE syntaxin disappeared from newly formed cell walls in fra2 earlier than in the wild-type. Taken together, these observations indicate that delayed cytokinesis, due to faulty phragmoplast organization and expansion, results in a loss of synchronization between cell plate growth and its chemical maturation.

ACS Style

Emmanuel Panteris; Anna Kouskouveli; Dimitris Pappas; Ioannis-Dimosthenis S. Adamakis. Cytokinesis in fra2 Arabidopsis thaliana p60-katanin Mutant: Defects in Cell Plate/Daughter Wall Formation. 2021, 1 .

AMA Style

Emmanuel Panteris, Anna Kouskouveli, Dimitris Pappas, Ioannis-Dimosthenis S. Adamakis. Cytokinesis in fra2 Arabidopsis thaliana p60-katanin Mutant: Defects in Cell Plate/Daughter Wall Formation. . 2021; ():1.

Chicago/Turabian Style

Emmanuel Panteris; Anna Kouskouveli; Dimitris Pappas; Ioannis-Dimosthenis S. Adamakis. 2021. "Cytokinesis in fra2 Arabidopsis thaliana p60-katanin Mutant: Defects in Cell Plate/Daughter Wall Formation." , no. : 1.

Journal article
Published: 17 December 2020 in International Journal of Molecular Sciences
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Microcystins (MCs) are cyanobacterial toxins and potent inhibitors of protein phosphatases 1 (PP1) and 2A (PP2A), which are involved in plant cytoskeleton (microtubules and F-actin) organization. Therefore, studies on the toxicity of cyanobacterial products on plant cells have so far been focused on MCs. In this study, we investigated the effects of extracts from 16 (4 MC-producing and 12 non-MC-producing) cyanobacterial strains from several habitats, on various enzymes (PP1, trypsin, elastase), on the plant cytoskeleton and H2O2 levels in Oryza sativa (rice) root cells. Seedling roots were treated for various time periods (1, 12, and 24 h) with aqueous cyanobacterial extracts and underwent either immunostaining for α-tubulin or staining of F-actin with fluorescent phalloidin. 2,7-dichlorofluorescein diacetate (DCF-DA) staining was performed for H2O2 imaging. The enzyme assays confirmed the bioactivity of the extracts of not only MC-rich (MC+), but also MC-devoid (MC−) extracts, which induced major time-dependent alterations on both components of the plant cytoskeleton. These findings suggest that a broad spectrum of bioactive cyanobacterial compounds, apart from MCs or other known cyanotoxins (such as cylindrospermopsin), can affect plants by disrupting the cytoskeleton.

ACS Style

Dimitris Pappas; Manthos Panou; Ioannis-Dimosthenis S. Adamakis; Spyros Gkelis; Emmanuel Panteris. Beyond Microcystins: Cyanobacterial Extracts Induce Cytoskeletal Alterations in Rice Root Cells. International Journal of Molecular Sciences 2020, 21, 9649 .

AMA Style

Dimitris Pappas, Manthos Panou, Ioannis-Dimosthenis S. Adamakis, Spyros Gkelis, Emmanuel Panteris. Beyond Microcystins: Cyanobacterial Extracts Induce Cytoskeletal Alterations in Rice Root Cells. International Journal of Molecular Sciences. 2020; 21 (24):9649.

Chicago/Turabian Style

Dimitris Pappas; Manthos Panou; Ioannis-Dimosthenis S. Adamakis; Spyros Gkelis; Emmanuel Panteris. 2020. "Beyond Microcystins: Cyanobacterial Extracts Induce Cytoskeletal Alterations in Rice Root Cells." International Journal of Molecular Sciences 21, no. 24: 9649.

Preprint
Published: 26 November 2020
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Microcystins (MCs) are cyanobacterial toxins and potent inhibitors of protein phosphatases 1 (PP1) and 2A (PP2A), which are involved in plant cytoskeleton (microtubules and F-actin) organization. Therefore, studies on the toxicity of cyanobacterial products on plant cells have so far being focused on MCs. In this study, we investigated the effects of extracts from 16 (4 MC-producing and 12 non-MC-producing) cyanobacterial strains from several habitats, on various enzymes (PP1, trypsin, elastase), on the plant cytoskeleton and H2O2 levels in Oryza sativa (rice) root cells. Seedling roots were treated for various time periods (1, 12 and 24h) with aqueous cyanobacterial extracts and underwent either immunostaining for α-tubulin or staining of F-actin with fluorescent phalloidin. DCF-DA staining was performed for H2O2 imaging. The enzyme assays confirmed the bioactivity of the extracts of not only MC-rich (MC+), but also MC-devoid (MC-) extracts, which induced major time-dependent alterations on both components of the plant cytoskeleton. These findings suggest that a broad spectrum of bioactive cyanobacterial compounds, apart from MCs or other known cyanotoxins (such as cylindrospermopsin), can affect plants by disrupting the cytoskeleton.

ACS Style

Dimitris Pappas; Manthos Panou; Ioannis-Dimosthenis S. Adamakis; Spyros Gkelis; Emmanuel Panteris. Beyond Microcystins: Cyanobacterial Extracts Induce Cytoskeletal Alterations in Rice Root Cells. 2020, 1 .

AMA Style

Dimitris Pappas, Manthos Panou, Ioannis-Dimosthenis S. Adamakis, Spyros Gkelis, Emmanuel Panteris. Beyond Microcystins: Cyanobacterial Extracts Induce Cytoskeletal Alterations in Rice Root Cells. . 2020; ():1.

Chicago/Turabian Style

Dimitris Pappas; Manthos Panou; Ioannis-Dimosthenis S. Adamakis; Spyros Gkelis; Emmanuel Panteris. 2020. "Beyond Microcystins: Cyanobacterial Extracts Induce Cytoskeletal Alterations in Rice Root Cells." , no. : 1.

Research paper
Published: 08 April 2020 in Plant Biology
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Microcystins are toxins produced by cyanobacteria, notorious for negatively affecting a wide range of living organisms, among which several plant species. Although microtubules are a well‐established target of microcystin toxicity, its effect on filamentous actin (F‐actin) in plant cells has not been studied yet. Τhe effects of microcystin‐LR (MC‐LR) and the extract of a microcystin‐producing freshwater cyanobacterial strain (Microcystis flos‐aquae TAU‐MAC 1510) on the cytoskeleton (F‐actin and microtubules) of Oryza sativa (rice) root cells, were studied by light, confocal, and transmission electron microscopy. Considering the role of F‐actin in endomembrane system distribution, the endoplasmic reticulum and the Golgi apparatus in extract‐treated cells were also examined. F‐actin in both MC‐LR‐ and extract‐treated meristematic and differentiating root cells exhibited time‐dependent alterations, ranging from disorientation and bundling to the formation of ring‐like structures, eventually resulting to a collapse of the F‐actin network at longer treatments. Disorganization and eventual depolymerization of microtubules, as well as abnormal chromatin condensation were observed following treatment with the extract, effects which could be attributed to microcystins and other bioactive compounds. Moreover, cell cycle progression was inhibited in extract‐treated roots, specifically affecting the mitotic events. As a consequence of F‐actin network disorganization, endoplasmic reticulum elements appeared stacked and diminished, while Golgi dictyosomes appeared aggregated. These results support that F‐actin is a prominent target of MC‐LR, both in pure form and as an extract ingredient. Endomembrane system alterations can also be attributed to the effects of cyanobacterial bioactive compounds (including microcystins) on F‐actin cytoskeleton.

ACS Style

D. Pappas; S. Gkelis; E. Panteris. The effects of microcystin‐LR in Oryza sativa root cells: F‐actin as a new target of cyanobacterial toxicity. Plant Biology 2020, 22, 839 -849.

AMA Style

D. Pappas, S. Gkelis, E. Panteris. The effects of microcystin‐LR in Oryza sativa root cells: F‐actin as a new target of cyanobacterial toxicity. Plant Biology. 2020; 22 (5):839-849.

Chicago/Turabian Style

D. Pappas; S. Gkelis; E. Panteris. 2020. "The effects of microcystin‐LR in Oryza sativa root cells: F‐actin as a new target of cyanobacterial toxicity." Plant Biology 22, no. 5: 839-849.

Preprint content
Published: 18 February 2020
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Microcystins are toxins produced by cyanobacteria, notorious for negatively affecting a wide range of living organisms, among which several plant species. Although microtubules are a well-established target of microcystin toxicity, its effect on filamentous actin (F-actin) in plant cells has not been studied yet.The effects of microcystin-LR (MC-LR) and the extract of a microcystin-producing freshwater cyanobacterial strain (Microcystis flos-aquae TAU-MAC 1510) on the cytoskeleton (F-actin and microtubules) of Oryza sativa (rice) root cells, were studied by light, confocal, and transmission electron microscopy. Considering the role of F-actin in endomembrane system distribution, the endoplasmic reticulum and the Golgi apparatus in extract-treated cells were also examined.F-actin in both MC-LR- and extract-treated meristematic and differentiating root cells exhibited time-dependent alterations, ranging from disorientation and bundling to the formation of ring-like structures, eventually resulting to a collapse of the F-actin network at longer treatments. Disorganization and eventual depolymerization of microtubules, as well as abnormal chromatin condensation were observed following treatment with the extract, effects which could be attributed to microcystins and other bioactive compounds. Moreover, cell cycle progression was inhibited in extract-treated roots, specifically affecting the mitotic events. As a consequence of F-actin network disorganization, endoplasmic reticulum elements appeared stacked and diminished, while Golgi dictyosomes appeared aggregated.These results support that F-actin is a prominent target of MC-LR, both in pure form and as an extract ingredient. Endomembrane system alterations can also be attributed to the effects of cyanobacterial bioactive compounds (including microcystins) on F-actin cytoskeleton.

ACS Style

Dimitris Pappas; Spyros Gkelis; Emmanuel Panteris. The effects of microcystin-LR in Oryza sativa root cells: F-actin as a new target of cyanobacterial toxicity. 2020, 1 .

AMA Style

Dimitris Pappas, Spyros Gkelis, Emmanuel Panteris. The effects of microcystin-LR in Oryza sativa root cells: F-actin as a new target of cyanobacterial toxicity. . 2020; ():1.

Chicago/Turabian Style

Dimitris Pappas; Spyros Gkelis; Emmanuel Panteris. 2020. "The effects of microcystin-LR in Oryza sativa root cells: F-actin as a new target of cyanobacterial toxicity." , no. : 1.