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Spatiotemporal control of cell division is essential for the growth and development of multicellular organisms. In plant cells, proper cell plate insertion during cytokinesis relies on the premitotic establishment of the division plane at the cell cortex. Two plant-specific cytoskeleton arrays, the preprophase band (PPB) and the phragmoplast, play important roles in division-plane orientation and cell plate formation, respectively1. Microtubule organization and dynamics and their communication with membranes at the cortex and cell plate are coordinated by multiple, mostly distinct microtubule-associated proteins2. How division-plane selection and establishment are linked, however, is still unknown. Here, we report members of the Arabidopsis IQ67 DOMAIN (IQD) family3 as microtubule-targeted proteins that localize to the PPB and phragmoplast and additionally reside at the cell plate and a polarized cortical region including the cortical division zone (CDZ). IQDs physically interact with PHRAGMOPLAST ORIENTING KINESIN (POK) proteins4,5 and PLECKSTRIN HOMOLOGY GTPase ACTIVATING (PHGAP) proteins6, which are core components of the CDZ1. The loss of IQD function impairs PPB formation and affects CDZ recruitment of POKs and PHGAPs, resulting in division-plane positioning defects. We propose that IQDs act as cellular scaffolds that facilitate PPB formation and CDZ set-up during symmetric cell division. The IQ67 DOMAIN (IQD) family are plant-specific calmodulin-binding proteins. Several members are associated with the microtubule cytoskeleton, and now IQD6, IQD7 and IQD8 are characterized as functioning in the set-up of the cell division plane in the root meristem of Arabidopsis.
Pratibha Kumari; Pradeep Dahiya; Pantelis Livanos; Luise Zergiebel; Malte Kölling; Yvonne Poeschl; Gina Stamm; Arvid Hermann; Steffen Abel; Sabine Müller; Katharina Bürstenbinder. IQ67 DOMAIN proteins facilitate preprophase band formation and division-plane orientation. Nature Plants 2021, 7, 739 -747.
AMA StylePratibha Kumari, Pradeep Dahiya, Pantelis Livanos, Luise Zergiebel, Malte Kölling, Yvonne Poeschl, Gina Stamm, Arvid Hermann, Steffen Abel, Sabine Müller, Katharina Bürstenbinder. IQ67 DOMAIN proteins facilitate preprophase band formation and division-plane orientation. Nature Plants. 2021; 7 (6):739-747.
Chicago/Turabian StylePratibha Kumari; Pradeep Dahiya; Pantelis Livanos; Luise Zergiebel; Malte Kölling; Yvonne Poeschl; Gina Stamm; Arvid Hermann; Steffen Abel; Sabine Müller; Katharina Bürstenbinder. 2021. "IQ67 DOMAIN proteins facilitate preprophase band formation and division-plane orientation." Nature Plants 7, no. 6: 739-747.
Leaf spongy mesophyll cells form an interconnected network of branched cells and intercellular spaces to maximize the surface area available for light capture and photosynthetic gas exchange. To investigate the morphogenetic events leading to cell separation and branching in Arabidopsis thaliana, we used mesophyll-specific promoters to facilitate imaging of mesophyll cell shape and microtubule (MT) organization over multiple spatiotemporal scales without interference from the overlying epidermal cells. We show that cells enlarge by selective expansion of cell wall regions in contact with intercellular spaces. Cell-cell contacts remain relatively fixed in size, forming the termini of interconnecting branches. Surprisingly, classic schizogeny (de-adhesion of neighboring cells) is relatively infrequent, being related to the local topology of cell junctions during early expansion. Intercellular spaces cue the position of stable MT bundles, which in turn promote efficient dilation of intercellular spaces and cell branching. Our data provide insights into mesophyll morphogenesis and MT organization and lay the groundwork for future investigations.© American Society of Plant Biologists 2020. All rights reserved. For permissions, please email: [email protected]
Sabine Müller; Pantelis Livanos; Zhang L; Mcevoy D; Le Y; Ambrose C. Faculty Opinions recommendation of Live imaging of microtubule organization, cell expansion, and intercellular space formation in Arabidopsis leaf spongy mesophyll cells. Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature 2021, 33, 1 .
AMA StyleSabine Müller, Pantelis Livanos, Zhang L, Mcevoy D, Le Y, Ambrose C. Faculty Opinions recommendation of Live imaging of microtubule organization, cell expansion, and intercellular space formation in Arabidopsis leaf spongy mesophyll cells. Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature. 2021; 33 (3):1.
Chicago/Turabian StyleSabine Müller; Pantelis Livanos; Zhang L; Mcevoy D; Le Y; Ambrose C. 2021. "Faculty Opinions recommendation of Live imaging of microtubule organization, cell expansion, and intercellular space formation in Arabidopsis leaf spongy mesophyll cells." Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature 33, no. 3: 1.
The bipolar mitotic spindle is a highly conserved structure among eukaryotes that mediates chromosome alignment and segregation. Spindle assembly and size control are facilitated by force-generating microtubule-dependent motor proteins known as kinesins. In animals, kinesin-12 cooperates with kinesin-5 to produce outward-directed forces necessary for spindle assembly. In plants, the relevant molecular mechanisms for spindle formation are poorly defined. While an Arabidopsis thaliana kinesin-5 ortholog has been identified, the kinesin-12 ortholog in plants remains elusive. In this study, we provide experimental evidence for the function of Arabidopsis KINESIN-12E in spindle assembly. In kinesin-12e mutants, a delay in spindle assembly is accompanied by the reduction of spindle size, demonstrating that KINESIN-12E contributes to mitotic spindle architecture. Kinesin-12E localization is mitosis-stage specific, beginning with its perinuclear accumulation during prophase. Upon nuclear envelope breakdown, KINESIN-12E decorates subpopulations of microtubules in the spindle and becomes progressively enriched in the spindle midzone. Furthermore, during cytokinesis, KINESIN-12E shares its localization at the phragmoplast midzone with several functionally diversified Arabidopsis KINESIN-12 members. Changes in the kinetochore and in prophase and metaphase spindle dynamics occur in the absence of KINESIN-12E, suggest it might play an evolutionarily conserved role during spindle formation similar to its spindle-localized animal kinesin-12 orthologs.
Arvid Herrmann; Pantelis Livanos; Steffi Zimmermann; Kenneth Berendzen; Leander Rohr; Elisabeth Lipka; Sabine Müller. KINESIN-12E regulates metaphase spindle flux and helps control spindle size in Arabidopsis. The Plant Cell 2020, 33, 27 -43.
AMA StyleArvid Herrmann, Pantelis Livanos, Steffi Zimmermann, Kenneth Berendzen, Leander Rohr, Elisabeth Lipka, Sabine Müller. KINESIN-12E regulates metaphase spindle flux and helps control spindle size in Arabidopsis. The Plant Cell. 2020; 33 (1):27-43.
Chicago/Turabian StyleArvid Herrmann; Pantelis Livanos; Steffi Zimmermann; Kenneth Berendzen; Leander Rohr; Elisabeth Lipka; Sabine Müller. 2020. "KINESIN-12E regulates metaphase spindle flux and helps control spindle size in Arabidopsis." The Plant Cell 33, no. 1: 27-43.
Cell wall assembly requires harmonized deposition of cellulose and matrix polysaccharides. Cortical microtubules orient the deposition of cellulose by guiding the trajectory of cellulose synthase complexes. Vesicles containing matrix polysaccharides are thought to be transported by the FRAGILE FIBER1 (FRA1) kinesin to facilitate their secretion along cortical microtubules. The cortical microtubule cytoskeleton thus may provide a platform to coordinate the delivery of cellulose and matrix polysaccharides, but the underlying molecular mechanisms remain unknown. Here, we show that the tail region of the Arabidopsis (Arabidopsis thaliana) FRA1 kinesin physically interacts with cellulose synthase-microtubule uncoupling (CMU) proteins that are important for the microtubule-dependent guidance of cellulose synthase complexes. Interaction with CMUs did not affect microtubule binding or motility of the FRA1 kinesin but differentially affected the protein levels and microtubule localization of CMU1 and CMU2, thus regulating the lateral stability of cortical microtubules. Phosphorylation of the FRA1 tail region inhibited binding to CMUs and consequently reversed the extent of cortical microtubule decoration by CMU1 and CMU2. Genetic experiments demonstrated the significance of this interaction to the growth and reproduction of Arabidopsis plants. We propose that modulation of CMU protein levels and microtubule localization by FRA1 provides a mechanism that stabilizes the sites of deposition of both cellulose and matrix polysaccharides.© 2020 American Society of Plant Biologists. All rights reserved.
Sabine Müller; Pantelis Livanos; Ganguly A; Zhu C; Chen W; Dixit R. Faculty Opinions recommendation of FRA1 Kinesin Modulates the Lateral Stability of Cortical Microtubules through Cellulose Synthase-Microtubule Uncoupling Proteins. Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature 2020, 32, 1 .
AMA StyleSabine Müller, Pantelis Livanos, Ganguly A, Zhu C, Chen W, Dixit R. Faculty Opinions recommendation of FRA1 Kinesin Modulates the Lateral Stability of Cortical Microtubules through Cellulose Synthase-Microtubule Uncoupling Proteins. Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature. 2020; 32 (8):1.
Chicago/Turabian StyleSabine Müller; Pantelis Livanos; Ganguly A; Zhu C; Chen W; Dixit R. 2020. "Faculty Opinions recommendation of FRA1 Kinesin Modulates the Lateral Stability of Cortical Microtubules through Cellulose Synthase-Microtubule Uncoupling Proteins." Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature 32, no. 8: 1.
The organization of cellulose microfibrils is critical for the strength and growth of plant cell walls. Microtubules have been shown to play a key role in controlling microfibril organization by guiding cellulose synthase complexes [1-4]. However, cellulose synthase trajectories can be maintained when microtubules are removed by drugs, suggesting a separate guidance mechanism is also at play [1, 5, 6]. By slowing down microtubule dynamics, we reveal such a mechanism by showing that cellulose synthase complexes can interact with the trails left by other complexes, causing them to follow the trails or disappear. The stability of the trails, together with the sensitivity of their directions to cellulase treatment, indicates they most likely reflect nascent cellulose microfibrils. Over many hours, this autonomous mechanism alone can lead to a change in the dominant orientation of cellulose synthase trajectories. However, the mechanism can be overridden by the microtubule guidance system. Our findings suggest a dual guidance model, in which an autonomous system, involving interaction between cellulose synthases and microfibrils, can maintain aligned cellulose synthase trajectories, while a microtubule guidance system allows alignments to be steered by environmental and developmental cues.Copyright © 2019 The Author(s). Published by Elsevier Ltd.. All rights reserved.
Sabine Müller; Pantelis Livanos. Faculty Opinions recommendation of Interaction between Autonomous and Microtubule Guidance Systems Controls Cellulose Synthase Trajectories. Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature 2020, 1 .
AMA StyleSabine Müller, Pantelis Livanos. Faculty Opinions recommendation of Interaction between Autonomous and Microtubule Guidance Systems Controls Cellulose Synthase Trajectories. Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature. 2020; ():1.
Chicago/Turabian StyleSabine Müller; Pantelis Livanos. 2020. "Faculty Opinions recommendation of Interaction between Autonomous and Microtubule Guidance Systems Controls Cellulose Synthase Trajectories." Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature , no. : 1.
Kinesin-12 family members are characterized by an N-terminal motor domain and the extensive presence of coiled-coil domains. Animal orthologs display microtubule plus-end directed motility, bundling of parallel and antiparallel microtubules, plus-end stabilization, and they play a crucial role in spindle assembly. In plants, kinesin-12 members mediate a number of developmental processes including male gametophyte, embryo, seedling, and seed development. At the cellular level, they participate in critical events during cell division. Several kinesin-12 members localize to the phragmoplast midzone, interact with isoforms of the conserved microtubule cross-linker MICROTUBULE-ASSOCIATED PROTEIN 65 (MAP65) family, and are required for phragmoplast stability and expansion, as well as for proper cell plate development. Throughout cell division, a subset of kinesin-12 reside, in addition or exclusively, at the cortical division zone and mediate the accurate guidance of the phragmoplast. This review aims to summarize the current knowledge on kinesin-12 in plants and shed some light onto the heterogeneous localization and domain architecture, which potentially conceals functional diversification.
Sabine Müller; Pantelis Livanos. Plant Kinesin-12: Localization Heterogeneity and Functional Implications. International Journal of Molecular Sciences 2019, 20, 4213 .
AMA StyleSabine Müller, Pantelis Livanos. Plant Kinesin-12: Localization Heterogeneity and Functional Implications. International Journal of Molecular Sciences. 2019; 20 (17):4213.
Chicago/Turabian StyleSabine Müller; Pantelis Livanos. 2019. "Plant Kinesin-12: Localization Heterogeneity and Functional Implications." International Journal of Molecular Sciences 20, no. 17: 4213.
Plant cells divide their cytoplasmic content by forming a new membrane compartment, the cell plate, via a rerouting of the secretory pathway toward the division plane aided by a dynamic cytoskeletal apparatus known as the phragmoplast. The phragmoplast expands centrifugally and directs the cell plate to the preselected division site at the plasma membrane to fuse with the parental wall. The division site is transiently decorated by the cytoskeletal preprophase band in preprophase and prophase, whereas a number of proteins discovered over the last decade reside continuously at the division site and provide a lasting spatial reference for phragmoplast guidance. Recent studies of membrane fusion at the cell plate have revealed the contribution of functionally conserved eukaryotic proteins to distinct stages of cell plate biogenesis and emphasize the coupling of cell plate formation with phragmoplast expansion. Together with novel findings concerning preprophase band function and the setup of the division site, cytokinesis and its spatial control remain an open-ended field with outstanding and challenging questions to resolve.
Pantelis Livanos; Sabine Müller. Division Plane Establishment and Cytokinesis. Annual Review of Plant Biology 2019, 70, 239 -267.
AMA StylePantelis Livanos, Sabine Müller. Division Plane Establishment and Cytokinesis. Annual Review of Plant Biology. 2019; 70 (1):239-267.
Chicago/Turabian StylePantelis Livanos; Sabine Müller. 2019. "Division Plane Establishment and Cytokinesis." Annual Review of Plant Biology 70, no. 1: 239-267.
Kinesins are versatile nano‐machines that utilize variable non‐motor domains to tune specific motor microtubule encounters. During plant cytokinesis, the kinesin‐12 orthologs, PHRAGMOPLAST ORIENTING KINESIN (POK)1 and POK2, are essential for rapid centrifugal expansion of the cytokinetic apparatus, the phragmoplast, toward a pre‐selected cell plate fusion site at the cell cortex. Here, we report on the spatio‐temporal localization pattern of POK2, mediated by distinct protein domains. Functional dissection of POK2 domains revealed the association of POK2 with the site of the future cell division plane and with the phragmoplast during cytokinesis. Accumulation of POK2 at the phragmoplast midzone depends on its functional POK2 motor domain and is fine‐tuned by its carboxy‐terminal region that also directs POK2 to the division site. Furthermore, POK2 likely stabilizes the phragmoplast midzone via interaction with the conserved microtubule‐associated protein MAP65‐3/PLEIADE, a well‐established microtubule cross‐linker. Collectively, our results suggest that dual localized POK2 plays multiple roles during plant cell division.
Arvid Herrmann; Pantelis Livanos; Elisabeth Lipka; Astrid Gadeyne; Marie‐Theres Hauser; Daniël Van Damme; Sabine Müller. Dual localized kinesin‐12 POK 2 plays multiple roles during cell division and interacts with MAP 65‐3. EMBO reports 2018, 19, e46085 .
AMA StyleArvid Herrmann, Pantelis Livanos, Elisabeth Lipka, Astrid Gadeyne, Marie‐Theres Hauser, Daniël Van Damme, Sabine Müller. Dual localized kinesin‐12 POK 2 plays multiple roles during cell division and interacts with MAP 65‐3. EMBO reports. 2018; 19 (9):e46085.
Chicago/Turabian StyleArvid Herrmann; Pantelis Livanos; Elisabeth Lipka; Astrid Gadeyne; Marie‐Theres Hauser; Daniël Van Damme; Sabine Müller. 2018. "Dual localized kinesin‐12 POK 2 plays multiple roles during cell division and interacts with MAP 65‐3." EMBO reports 19, no. 9: e46085.
Selenium Βinding Protein (SBP, originally termed SBP56) was identified in mouse liver as a cytosolic protein that could bind radioactive selenium. SBPs are highly conserved proteins present in a wide array of species across all kingdoms and are likely to be involved in selenium metabolism. In Arabidopsis, the Selenium Binding Protein (SBP) gene family comprises three genes (AtSBP1, AtSBP2 and AtSBP3). AtSBP1and AtSBP2 are clustered in a head-to-tail arrangement on chromosome IV, while AtSBP3 is located on chromosome III. In this work, we studied the promoter activity of the Arabidopsis SBP genes, determined their tissue specificity and showed that they are differentially regulated by sodium selenite and sodium selenate. All three SBP genes are upregulated in response to externally applied selenium compounds and the antioxidant NAC selectively downregulates SBP2. Although the effect on SBP2 levels was the most prominent, in all cases, the concurrent exposure of plants to selenite and the antioxidant supressed the expression of the SBP genes. We provide evidence that (at least) SBP1 expression is tightly linked to detoxification processes related to oxidative stress, since it is downregulated in the presence of NAC in selenium-treated plants. Furthermore, our results suggest that SBP genes may participate in the mechanisms that sense redox imbalance.
Chrysanthi Valassakis; Pantelis Livanos; Martha Minopetrou; Kosmas Haralampidis; Andreas Roussis. Promoter analysis and functional implications of the selenium binding protein (SBP) gene family in Arabidopsis thaliana. Journal of Plant Physiology 2018, 224-225, 19 -29.
AMA StyleChrysanthi Valassakis, Pantelis Livanos, Martha Minopetrou, Kosmas Haralampidis, Andreas Roussis. Promoter analysis and functional implications of the selenium binding protein (SBP) gene family in Arabidopsis thaliana. Journal of Plant Physiology. 2018; 224-225 ():19-29.
Chicago/Turabian StyleChrysanthi Valassakis; Pantelis Livanos; Martha Minopetrou; Kosmas Haralampidis; Andreas Roussis. 2018. "Promoter analysis and functional implications of the selenium binding protein (SBP) gene family in Arabidopsis thaliana." Journal of Plant Physiology 224-225, no. : 19-29.
BackgroundFormation of stomatal complexes in Poaceae is the outcome of three asymmetric and one symmetric cell division occurring in particular leaf protodermal cells. In this definite sequence of cell division events, the generation of subsidiary cells is of particular importance and constitutes an attractive model for studying local intercellular stimulation. In brief, an induction stimulus emitted by the guard cell mother cells (GMCs) triggers a series of polarization events in their laterally adjacent protodermal cells. This signal determines the fate of the latter cells, forcing them to divide asymmetrically and become committed to subsidiary cell mother cells (SMCs).ScopeThis article summarizes old and recent structural and molecular data mostly derived from Zea mays, focusing on the interplay between GMCs and SMCs, and on the unique polarization sequence occurring in both cell types. Recent evidence suggests that auxin operates as an inducer of SMC polarization/asymmetric division. The intercellular auxin transport is facilitated by the distribution of a specific transmembrane auxin carrier and requires reactive oxygen species (ROS). Interestingly, the local differentiation of the common cell wall between SMCs and GMCs is one of the earliest features of SMC polarization. Leucine-rich repeat receptor-like kinases, Rho-like plant GTPases as well as the SCAR/WAVE regulatory complex also participate in the perception of the morphogenetic stimulus and have been implicated in certain polarization events in SMCs. Moreover, the transduction of the auxin signal and its function are assisted by phosphatidylinositol-3-kinase and the products of the catalytic activity of phospholipases C and D.ConclusionIn the present review, the possible role(s) of each of the components in SMC polarization and asymmetric division are discussed, and an overall perspective on the mechanisms beyond these phenomena is provided.
P Apostolakos; Pantelis Livanos; Eleni Giannoutsou; Emmanuel Panteris; B Galatis. The intracellular and intercellular cross-talk during subsidiary cell formation in Zea mays: existing and novel components orchestrating cell polarization and asymmetric division. Annals of Botany 2018, 122, 679 -696.
AMA StyleP Apostolakos, Pantelis Livanos, Eleni Giannoutsou, Emmanuel Panteris, B Galatis. The intracellular and intercellular cross-talk during subsidiary cell formation in Zea mays: existing and novel components orchestrating cell polarization and asymmetric division. Annals of Botany. 2018; 122 (5):679-696.
Chicago/Turabian StyleP Apostolakos; Pantelis Livanos; Eleni Giannoutsou; Emmanuel Panteris; B Galatis. 2018. "The intracellular and intercellular cross-talk during subsidiary cell formation in Zea mays: existing and novel components orchestrating cell polarization and asymmetric division." Annals of Botany 122, no. 5: 679-696.
In plants, the partitioning of daughter cells during cytokinesis is achieved via physical insertion of a membranous cell plate within the dividing parent cell. It is a cellular process of extensive protein secretion and membrane trafficking toward the plane of cell division and the cytoskeleton is an important facilitator of this process. A specialized cytoskeletal array termed phragmoplast expands centrifugally throughout cytokinesis and directs, mostly Golgi-derived vesicles that ultimately fuse to form the developing cell plate. The function of the phragmoplast in guiding cell plate synthesis has strongly motivated many scientists to monitor its dynamic behavior. In this chapter, we present an overview of basic principles and methods concerning the live imaging of cytokinetic plant cells using confocal laser scanning microscopy (CLSM) and the analysis of phragmoplast expansion.
Pantelis Livanos; Mayank Chugh; Sabine Müller. Analysis of Phragmoplast Kinetics During Plant Cytokinesis. Advanced Structural Safety Studies 2017, 1662, 137 -150.
AMA StylePantelis Livanos, Mayank Chugh, Sabine Müller. Analysis of Phragmoplast Kinetics During Plant Cytokinesis. Advanced Structural Safety Studies. 2017; 1662 ():137-150.
Chicago/Turabian StylePantelis Livanos; Mayank Chugh; Sabine Müller. 2017. "Analysis of Phragmoplast Kinetics During Plant Cytokinesis." Advanced Structural Safety Studies 1662, no. : 137-150.
Arabidopsis thaliana flowering time mutants revealed the function of numerous genes that regulate the transition from vegetative to reproductive growth. Analyses of their loci have shown that many of them act as chromatin modifiers. In this study, a combination of molecular and genetic approaches have been implemented, to characterize the function of APRF1 (ANTHESIS POMOTING FACTOR 1) gene in A. thaliana and to investigate its role in plant development. APRF1 encodes for a low molecular weight nuclear WDR protein which displays functional homology to the Swd2 protein, an essential subunit of the yeast histone methylation COMPASS complex. Compared to WT plants, total loss-of-function aprf1 mutants exhibited shoot apical meristem (SAM) alterations and increased growth rates. However, the vegetative phase of aprf1 plants was prolonged and bolting was delayed, indicating an impairment in flowering under long days (LD). On the contrary, overexpression of APRF1 accelerates flowering. Consistent with the late flowering phenotype, the molecular data confirmed that FLC and SOC1 expression were significantly altered in the aprf1 mutants. Our data suggest that APRF1 acts upstream of FLC and promotes flowering under LD.
Georgios Kapolas; Despoina Beris; Efthimia Katsareli; Pantelis Livanos; Aris Zografidis; Andreas Roussis; Dimitra Milioni; Kosmas Haralampidis. APRF1 promotes flowering under long days in Arabidopsis thaliana. Plant Science 2016, 253, 141 -153.
AMA StyleGeorgios Kapolas, Despoina Beris, Efthimia Katsareli, Pantelis Livanos, Aris Zografidis, Andreas Roussis, Dimitra Milioni, Kosmas Haralampidis. APRF1 promotes flowering under long days in Arabidopsis thaliana. Plant Science. 2016; 253 ():141-153.
Chicago/Turabian StyleGeorgios Kapolas; Despoina Beris; Efthimia Katsareli; Pantelis Livanos; Aris Zografidis; Andreas Roussis; Dimitra Milioni; Kosmas Haralampidis. 2016. "APRF1 promotes flowering under long days in Arabidopsis thaliana." Plant Science 253, no. : 141-153.
Reactive oxygen species (ROS) are emerging players in several biological processes. The present work investigates their potential involvement in plant cytokinesis by the application of reagents disturbing ROS homeostasis in root-tip cells of Triticum turgidum. In particular, the NADPH-oxidase inhibitor diphenylene iodonium, the ROS scavenger N-acetyl-cysteine, and menadione that leads to ROS overproduction were used. The effects on cytokinetic cells were examined using light, fluorescence, and transmission electron microscopy. ROS imbalance had a great impact on the cytokinetic process including the following: (a) formation of atypical “phragmoplasts” incapable of guiding vesicles to the equatorial plane, (b) inhibition of the dictyosomal and/or endosomal vesicle production that provides the developing cell plates with membranous and matrix polysaccharidic material, (c) disturbance of the fusion processes between vesicles arriving on the cell plate plane, (d) disruption of endocytic vesicle production that mediates the removal of the excess membrane material from the developing cell plate, and (e) the persistence of large callose depositions in treated cell plates. Consequently, either elevated or low ROS levels in cytokinetic root-tip cells resulted in a total inhibition of cell plate assembly or the formation of aberrant cell plates, depending on the stage of the affected cytokinetic cells. The latter failed to expand towards cell cortex and hence to give rise to complete daughter cell wall. These data revealed for the first time the necessity of ROS homeostasis for accomplishment of plant cytokinesis, since it seems to be a prerequisite for almost every aspect of this process.
Pantelis Livanos; Basil Galatis; Hartmut Quader; Panagiotis Apostolakos. ROS homeostasis as a prerequisite for the accomplishment of plant cytokinesis. Protoplasma 2016, 254, 569 -586.
AMA StylePantelis Livanos, Basil Galatis, Hartmut Quader, Panagiotis Apostolakos. ROS homeostasis as a prerequisite for the accomplishment of plant cytokinesis. Protoplasma. 2016; 254 (1):569-586.
Chicago/Turabian StylePantelis Livanos; Basil Galatis; Hartmut Quader; Panagiotis Apostolakos. 2016. "ROS homeostasis as a prerequisite for the accomplishment of plant cytokinesis." Protoplasma 254, no. 1: 569-586.
Ubiquitin mediated protein degradation constitutes one of the most complex post translational gene regulation mechanisms in eukaryotes. This fine-tuned proteolytic machinery is based on a vast number of E3 ubiquitin ligase complexes that mark target proteins with ubiquitin. The specificity is accomplished by a number of adaptor proteins that contain functional binding domains, including the WD40 repeat motif (WDRs). To date, only few of these proteins have been identified in plants. An RNAi mediated silencing approach was used here to functionally characterize the Arabidopsis thaliana ULCS1 gene, which encodes for a small molecular weight WDR protein. AtULCS1 interacts with the E3Cullin Ring Ligase subunit DDB1a, regulating most likely the degradation of specific proteins involved in the manifestation of diverse developmental events. Silencing of AtULCS1 results in sterile plants with pleiotropic phenotypes. Detailed analysis revealed that infertility is the outcome of anther indehiscence, which in turn is due to the impairment of the plants to accomplish secondary wall modifications. Furthermore, IREGULAR XYLEM gene expression and lignification is diminished in anther endothecium and the stem vascular tissue of the silenced plants. These data underline the importance of AtULCS1 in plant development and reproduction.
Despoina Beris; Georgios Kapolas; Pantelis Livanos; Andreas Roussis; Dimitra Milioni; Kosmas Haralampidis. RNAi-mediated silencing of the Arabidopsis thaliana ULCS1 gene, encoding a WDR protein, results in cell wall modification impairment and plant infertility. Plant Science 2016, 245, 71 -83.
AMA StyleDespoina Beris, Georgios Kapolas, Pantelis Livanos, Andreas Roussis, Dimitra Milioni, Kosmas Haralampidis. RNAi-mediated silencing of the Arabidopsis thaliana ULCS1 gene, encoding a WDR protein, results in cell wall modification impairment and plant infertility. Plant Science. 2016; 245 ():71-83.
Chicago/Turabian StyleDespoina Beris; Georgios Kapolas; Pantelis Livanos; Andreas Roussis; Dimitra Milioni; Kosmas Haralampidis. 2016. "RNAi-mediated silencing of the Arabidopsis thaliana ULCS1 gene, encoding a WDR protein, results in cell wall modification impairment and plant infertility." Plant Science 245, no. : 71-83.
Subsidiary cell generation in Poaceae is an outstanding example of local intercellular stimulation. An inductive stimulus emanates from the guard cell mother cells (GMCs) towards their laterally adjacent subsidiary cell mother cells (SMCs) and triggers the asymmetrical division of the latter. Indole-3-acetic acid (IAA) immunolocalization in Zea mays protoderm confirmed that the GMCs function as local sources of auxin and revealed that auxin is polarly accumulated between GMCs and SMCs in a timely-dependent manner. Besides, staining techniques showed that reactive oxygen species (ROS) exhibit a closely similar, also time-dependent, pattern of appearance suggesting ROS implication in subsidiary cell formation. This phenomenon was further investigated by using the specific NADPH-oxidase inhibitor diphenylene iodonium, the ROS scavenger N-acetyl-cysteine, menadione which leads to ROS overproduction, and H2O2. Treatments with diphenylene iodonium, N-acetyl-cysteine, and menadione specifically blocked SMC polarization and asymmetrical division. In contrast, H2O2 promoted the establishment of SMC polarity and subsequently subsidiary cell formation in “younger” protodermal areas. Surprisingly, H2O2 favored the asymmetrical division of the intervening cells of the stomatal rows leading to the creation of extra apical subsidiary cells. Moreover, H2O2 altered IAA localization, whereas synthetic auxin analogue 1-napthaleneacetic acid enhanced ROS accumulation. Combined treatments with ROS modulators along with 1-napthaleneacetic acid or 2,3,5-triiodobenzoic acid, an auxin efflux inhibitor, confirmed the crosstalk between ROS and auxin functioning during subsidiary cell generation. Collectively, our results demonstrate that ROS are critical partners of auxin during development of Z. mays stomatal complexes. The interplay between auxin and ROS seems to be spatially and temporarily regulated.
Pantelis Livanos; Basil Galatis; Panagiotis Apostolakos. Deliberate ROS production and auxin synergistically trigger the asymmetrical division generating the subsidiary cells in Zea mays stomatal complexes. Protoplasma 2015, 253, 1081 -1099.
AMA StylePantelis Livanos, Basil Galatis, Panagiotis Apostolakos. Deliberate ROS production and auxin synergistically trigger the asymmetrical division generating the subsidiary cells in Zea mays stomatal complexes. Protoplasma. 2015; 253 (4):1081-1099.
Chicago/Turabian StylePantelis Livanos; Basil Galatis; Panagiotis Apostolakos. 2015. "Deliberate ROS production and auxin synergistically trigger the asymmetrical division generating the subsidiary cells in Zea mays stomatal complexes." Protoplasma 253, no. 4: 1081-1099.
The data presented in this work revealed that in Zea mays the exogenously added auxins indole-3-acetic acid (IAA) and 1-napthaleneacetic acid (NAA), promoted the establishment of subsidiary cell mother cell (SMC) polarity and the subsequent subsidiary cell formation, while treatment with auxin transport inhibitors 2,3,5-triiodobenzoic acid (TIBA) and 1-napthoxyacetic acid (NOA) specifically blocked SMC polarization and asymmetrical division. Furthermore, in young guard cell mother cells (GMCs) the PIN1 auxin efflux carriers were mainly localized in the transverse GMC faces, while in the advanced GMCs they appeared both in the transverse and the lateral ones adjacent to SMCs. Considering that phosphatidyl-inositol-3-kinase (PI3K) is an active component of auxin signal transduction and that phospholipid signaling contributes in the establishment of polarity, treatments with the specific inhibitor of the PI3K LY294002 were carried out. The presence of LY294002 suppressed polarization of SMCs and prevented their asymmetrical division, whereas combined treatment with exogenously added NAA and LY294002 restricted the promotional auxin influence on subsidiary cell formation. These findings support the view that auxin is involved in Z. mays subsidiary cell formation, probably functioning as inducer of the asymmetrical SMC division. Collectively, the results obtained from treatments with auxin transport inhibitors and the appearance of PIN1 proteins in the lateral GMC faces indicate a local transfer of auxin from GMCs to SMCs. Moreover, auxin signal transduction seems to be mediated by the catalytic function of PI3K.
Pantelis Livanos; Eleni Giannoutsou; Panagiotis Apostolakos; Basil Galatis. Auxin as an inducer of asymmetrical division generating the subsidiary cells in stomatal complexes ofZea mays. Plant Signaling & Behavior 2015, 10, e984531 -e984531.
AMA StylePantelis Livanos, Eleni Giannoutsou, Panagiotis Apostolakos, Basil Galatis. Auxin as an inducer of asymmetrical division generating the subsidiary cells in stomatal complexes ofZea mays. Plant Signaling & Behavior. 2015; 10 (3):e984531-e984531.
Chicago/Turabian StylePantelis Livanos; Eleni Giannoutsou; Panagiotis Apostolakos; Basil Galatis. 2015. "Auxin as an inducer of asymmetrical division generating the subsidiary cells in stomatal complexes ofZea mays." Plant Signaling & Behavior 10, no. 3: e984531-e984531.
Plants have to deal with reactive oxygen species (ROS) production, since it could potentially cause severe damages to different cellular components. On the other hand, ROS functioning as important second messengers are implicated in various developmental processes and are transiently produced during biotic or abiotic stresses. Furthermore, the microtubules (MTs) play a primary role in plant development and appear as potent players in sensing stressful situations and in the subsequent cellular responses. Emerging evidence suggests that ROS affect MTs in multiple ways. The cellular redox status seems to be tightly coupled with MTs. ROS signals regulate the organization of tubulin cytoskeleton and induce tubulin modifications. This review aims at summarizing the signaling mechanisms and the key operators orchestrating the crosstalk between ROS and tubulin cytoskeleton in plant cells. The contribution of several molecules, including microtubule associated proteins, oxidases, kinases, phospholipases, and transcription factors, is highlighted.
Pantelis Livanos; Basil Galatis; Panagiotis Apostolakos. The interplay between ROS and tubulin cytoskeleton in plants. Plant Signaling & Behavior 2014, 9, e28069 .
AMA StylePantelis Livanos, Basil Galatis, Panagiotis Apostolakos. The interplay between ROS and tubulin cytoskeleton in plants. Plant Signaling & Behavior. 2014; 9 (3):e28069.
Chicago/Turabian StylePantelis Livanos; Basil Galatis; Panagiotis Apostolakos. 2014. "The interplay between ROS and tubulin cytoskeleton in plants." Plant Signaling & Behavior 9, no. 3: e28069.
Reactive oxygen species (ROS) imbalance is a stressful condition for plant cells accompanied by dramatic changes in tubulin cytoskeleton. Here, evidence is provided that alterations in ROS levels directly interfere with the phosphorylation state of a p38‐like MAPK in the angiosperms Triticum turgidum and Arabidopsis thaliana. Both oxidative stress generators and chemicals inducing ROS scavenging or decreasing ROS production resulted in the accumulation of a phospho‐p46 protein similar to p38‐MAPK. Importantly, the rhd2 A. thaliana mutants exhibited a remarkable increase in levels of phospho‐p46. The presence of the p38‐MAPK inhibitor SB203580 attenuated the response to ROS disturbance, prevented microtubule disappearance and resulted in a dramatic decrease in the number of atypical tubulin polymers. Moreover, in roots treated simultaneously with substances inducing ROS overproduction and others resulting in low ROS levels, phospho‐p46 levels and the organization of tubulin cytoskeleton were similar to controls. Collectively, our experimental data suggest, for the first time in plants, that p46 functions as a putative sensor of redox state, the activation of which initiates downstream signalling events leading to microtubule disruption and subsequent assembly of atypical tubulin polymers. Thus, p46 seems to participate in perception of ROS homeostasis disturbance as well as in cellular responses to redox imbalance.
Pantelis Livanos; Basil Galatis; Catherine Gaitanaki; Panagiotis Apostolakos. Phosphorylation of a p38-like MAPK is involved in sensing cellular redox state and drives atypical tubulin polymer assembly in angiosperms. Plant, Cell & Environment 2013, 37, 1130 -1143.
AMA StylePantelis Livanos, Basil Galatis, Catherine Gaitanaki, Panagiotis Apostolakos. Phosphorylation of a p38-like MAPK is involved in sensing cellular redox state and drives atypical tubulin polymer assembly in angiosperms. Plant, Cell & Environment. 2013; 37 (5):1130-1143.
Chicago/Turabian StylePantelis Livanos; Basil Galatis; Catherine Gaitanaki; Panagiotis Apostolakos. 2013. "Phosphorylation of a p38-like MAPK is involved in sensing cellular redox state and drives atypical tubulin polymer assembly in angiosperms." Plant, Cell & Environment 37, no. 5: 1130-1143.
Accumulated evidence indicates that ROS fluctuations play a critical role in cell division. Dividing plant cells rapidly respond to them. Experimental disturbance of ROS homeostasis affects: tubulin polymerization; PPB, mitotic spindle and phragmoplast assembly; nuclear envelope dynamics; chromosome separation and movement; cell plate formation. Dividing cells mainly accumulate at prophase and delay in passing through the successive cell division stages. Notably, many dividing root cells of the rhd2 Arabidopsis thaliana mutants, lacking the RHD2/AtRBOHC protein function, displayed aberrations, comparable to those induced by low ROS levels. Some protein molecules, playing key roles in signal transduction networks inducing ROS production, participate in cell division. NADPH oxidases and their regulators PLD, PI3K and ROP-GTPases, are involved in MT polymerization and organization. Cellular ROS oscillations function as messages rapidly transmitted through MAPK pathways inducing MAP activation, thus affecting MT dynamics and organization. RNS implication in cell division is also considered.
Pantelis Livanos; Panagiotis Apostolakos; Basil Galatis. Plant cell division. Plant Signaling & Behavior 2012, 7, 771 -778.
AMA StylePantelis Livanos, Panagiotis Apostolakos, Basil Galatis. Plant cell division. Plant Signaling & Behavior. 2012; 7 (7):771-778.
Chicago/Turabian StylePantelis Livanos; Panagiotis Apostolakos; Basil Galatis. 2012. "Plant cell division." Plant Signaling & Behavior 7, no. 7: 771-778.
In this study, the effects of disturbance of the reactive oxygen species (ROS) homeostasis on the organization of tubulin cytoskeleton in interphase and mitotic root‐tip cells of Triticum turgidum and Arabidopsis thaliana were investigated. Reduced ROS levels were obtained by treatment with diphenylene iodonium (DPI) and N‐acetyl‐cysteine, whereas menadione was applied to achieve ROS overproduction. Both increased and low ROS levels induced: (a) Macrotubule formation in cells with low ROS levels and tubulin paracrystals under oxidative stress. The protein MAP65‐1 was detected in treated cells, exhibiting a conformation comparable to that of the atypical tubulin polymers. (b) Disappearance of microtubules (MTs). (c) Inhibition of preprophase band formation. (d) Delay of the nuclear envelope breakdown at prometaphase. (e) Prevention of perinuclear tubulin polymer assembly in prophase cells. (f) Loss of bipolarity of prophase, metaphase and anaphase spindles. Interestingly, examination of the A. thaliana rhd2/At respiratory burst oxidase homolog C (rbohc) NADPH oxidase mutant, lacking RHD2/AtRBOHC, gave comparable results. Similarly to DPI, the decreased ROS levels in rhd2 root‐tip cells, interfered with MT organization and induced macrotubule assembly. These data indicate, for first time in plants, that ROS are definitely implicated in: (a) mechanisms controlling the assembly/disassembly of interphase, preprophase and mitotic MT systems and (b) mitotic spindle function. The probable mechanisms, by which ROS affect these processes, are discussed.
Pantelis Livanos; Basil Galatis; Hartmut Quader; Panagiotis Apostolakos. Disturbance of reactive oxygen species homeostasis induces atypical tubulin polymer formation and affects mitosis in root-tip cells of Triticum turgidum and Arabidopsis thaliana. Cytoskeleton 2011, 69, 1 -21.
AMA StylePantelis Livanos, Basil Galatis, Hartmut Quader, Panagiotis Apostolakos. Disturbance of reactive oxygen species homeostasis induces atypical tubulin polymer formation and affects mitosis in root-tip cells of Triticum turgidum and Arabidopsis thaliana. Cytoskeleton. 2011; 69 (1):1-21.
Chicago/Turabian StylePantelis Livanos; Basil Galatis; Hartmut Quader; Panagiotis Apostolakos. 2011. "Disturbance of reactive oxygen species homeostasis induces atypical tubulin polymer formation and affects mitosis in root-tip cells of Triticum turgidum and Arabidopsis thaliana." Cytoskeleton 69, no. 1: 1-21.