TICB 1364 No. of Pages 10 Opinion Plant Cytokinesis: Terminology for Structures and Processes Andrei Smertenko,1,* Farhah Assaad,2 František Baluška,3 Magdalena Bezanilla,4,23 Henrik Buschmann,5 Georgia Drakakaki,6 Marie-Theres Hauser,7 Marcel Janson,8 Yoshinobu Mineyuki,9 Ian Moore,10 Sabine Müller,11 Takashi Murata,12 Marisa S. Otegui,13 Emmanuel Panteris,14 Carolyn Rasmussen,15 Anne-Catherine Schmit,16 Jozef Šamaj,17 Lacey Samuels,18 L. Andrew Staehelin,19 Daniel Van Damme,20,21 Geoffrey Wasteneys,18 and Viktor Žárský22 Plant cytokinesis is orchestrated by a specialized structure, the phragmoplast. Trends The phragmoplast first occurred in representatives of Charophyte algae and A large number of phragmoplast pro- then became the main division apparatus in land plants. Major cellular activi- teins have been identified. ties, including cytoskeletal dynamics, vesicle trafficking, membrane assembly, and cell wall biosynthesis, cooperate in the phragmoplast under the guidance Electron microscopy/tomography stu- dies have produced nanoscale infor- of a complex signaling network. Furthermore, the phragmoplast combines mation about the architecture of plant-specific features with the conserved cytokinetic processes of animals, phragmoplast and cell plate assembly stages in cryofixed cells. fungi, and protists. As such, the phragmoplast represents a useful system for understanding both plant cell dynamics and the evolution of cytokinesis. We Novel components of the cortical divi- recognize that future research and knowledge transfer into other fields would sion zone and cell plate fusion site have fi been discovered. This information lays bene t from standardized terminology. Here, we propose such a lexicon of a foundation for understanding how terminology for specific structures and processes associated with plant plant cells memorize the division plane cytokinesis. throughout mitosis and how the cell plate is guided to its predetermined attachment site. Rationale for Updating Plant Cytokinesis Terminology MAP65 and plus end-directed kinesins Current plant cytokinesis terminology was developed using data generated by fluorescence contribute to the maintenance of the antiparallel overlap of phragmoplast fi fi microscopy of live or xed cells, electron microscopy of chemically or cryo xed cells, and microtubules. In addition, the MAP65- genetic strategies. As a consequence of different experimental approaches, and for historic –TRAPPII interaction plays a key role in reasons, the cytokinetic processes and structures are often referred to by different names. cell plate assembly. Because plant cytokinesis has become a useful model system for addressing specific ques- Actin filaments align parallel to micro- tions in plant biochemistry, cell biology, development, etc., we recognize that exchange of tubules in the phragmoplast, while information between scientists working in these diverse fields, as well as further advancement some microfilaments extend from cell of plant cytokinesis research, would benefit from a harmonized terminology. Here, we sum- plate margin to guide its expansion towards the fusion site. marize the steps,[376_TD$IF] and update terminology associated with two major processes in plant cytokinesis: determination of the cell division plane and assembly of the cell plate (Table 1). We also propose established markers for some processes and structures (Table 2). The 1Institute of Biological Chemistry, terminology proposed here uses cytokinesis in somatic cells as an example and takes Washington State University, Pullman, advantage of available structural information. Division in reproductive organs and specialized WA 99164, USA 2Botany Department, WZW, cell types involves similar processes, which appear to be structurally different [1]. For in-depth Technische Universität München, description of cytokinesis in somatic cells we refer to several recent reviews [2–6]. Terminology Freising, 85354 Germany Trends in Cell Biology, Month Year, Vol. xx, No. yy http://dx.doi.org/10.1016/j.tcb.2017.08.008 1 © 2017 Elsevier Ltd. All rights reserved. TICB 1364 No. of Pages 10 3Department of Plant Cell Biology, Table 1. Glossary of Plant[374_TD$IF] Cytokinesis Terminology IZMB, University of Bonn, Term Former terms Description Kirschallee 1, D-53115, Bonn, Germany Actin-depleted Cortical region of cytoplasm with few actin filaments that forms prior to 4Biology Department, University of zone (ADZ) nuclear envelope breakdown and usually coincides with the cortical Massachusetts, Amherst, MA 01003, division zone (CDZ). ADZ can be flanked by domains enriched in actin USA fi laments, known as a twin-peaks structure in some cell types. 5Botany Department, School of Cell division plane Anticipated or true position of the cell plate. Biology and Chemistry, Osnabrück University, Barbarastraße 11, 49076 Cell plate Membrane-polysaccharide compartment that partitions the Osnabrück, Germany cytoplasm after nuclear division. 6Department of Plant Sciences, University of California Davis, Davis, Cell plate assembly General term referring to all processes from cell plate biogenesis to CA 95616, USA maturation. 7Department of Applied Genetics and Cell plate assembly Amorphous scaffold system consisting of proteins and vesicles in Cell Biology, University of Natural matrix (CPAM) the phragmoplast midzone (150 nm thick) that is responsible for Resources and Life Sciences, Vienna, mobilization of protein complexes and vesicles involved in cell plate Austria 8 assembly. Laboratory of Cell Biology, Wageningen University, Cell plate attachment Process of cell plate anchoring and fusion to the parental plasma Droevendaalsesteeg 1, 6708 PB membrane and cell wall. Wageningen, The Netherlands 9 Cell plate biogenesis Generation of a membrane compartment via vesicle tethering and Department of Picobiology, Graduate School of Life Science, University of fusion inside the CPAM. Transport protein particle (TRAPP)II is the Hyogo, Shosha 2167, Himeji 671- predominant tethering complex. 2201, Japan Cell plate expansion Radial increase of the cell plate area during the ring and 10Department of Plant Sciences, discontinuous phragmoplast stages. Characterized by simultaneous University of Oxford, South Parks Rd., presence of different cell plate assembly stages from cytokinetic Oxford, OX1 3RB, UK 11 vesicle fusion to fenestrated sheet. Center for Plant Molecular Biology, University of Tübingen, Auf der Cell plate fusion site Cortical division site Location at which the cell plate fuses with the plasma membrane. Morgenstelle 32, 72076 Tübingen, Cell plate initiation Membrane trafficking and protein/protein interaction processes that Germany 12National Institute for Basic Biology, lead to formation of the cell plate assembly matrix. EXOCYST and Myodaiji, Okazaki 444-8585, Japan TRAPPII are both present. 13Departments of Botany and Cell plate maturation Chemical and structural modifications of the cell plate after Genetics, Laboratories of Cell attachment that result in cross-wall formation. and Molecular Biology, University of Wisconsin–Madison, WI, Central spindle Central region of the anaphase spindle containing antiparallel USA microtubules. 14Department of Botany, School of Cortical[375_TD$IF] division Zone (area) of the plasma membrane and adjacent cell wall that Biology, Aristotle University of zone (CDZ) marks the site where the cell plate will fuse with the cell wall. CDZ is Thessaloniki, Thessaloniki GR-541 24, Macedonia, Greece detectable during preprophase band (PPB) development and 15Center for Plant Cell Biology, persists until completion of cell plate assembly. CDZ possesses a Institute of Integrative Genome dynamic but distinct composition in relation to other plasma Biology, Department of Botany and membrane and cell wall regions. The PPB is a part of the CDZ until Plant Sciences, University of PPB disappears during nuclear envelope breakdown. California, Riverside, CA, USA 16 Cross-wall Cell plate after completing fusion with the parental[39_TD$IF] cell wall. The Institut de Biologie Moléculaire des EXOCYST is the predominant tethering complex during cross-wall Plantes, Centre National de La fi formation. Recherche Scienti que, Université de Strasbourg, F67084, Strasbourg- Cross-wall Chemical and structural modifications of the cross-wall that result in cedex, France transformation formation of the middle lamella. 17Centre of the Region Haná for Biotechnological and Agricultural Cytokinetic vesicles Cell-plate-forming Membrane vesicles that provide material for cell plate assembly. Research, Faculty of Science, Palacký vesicles Principally of Golgi and trans-Golgi network origin and carrying both University, Šlechtitelu 27, 783 71 biosynthetic and endocytic material. Olomouc, Czech Republic 18 Discontinuous Late, asymmetric Phragmoplast after unilateral docking to the plasma membrane. Department of Botany, University of phragmoplast British Columbia, Vancouver, BC, V6T 1Z4, Canada Disk phragmoplast Solid, early, young Phragmoplast at early cytokinetic stages, characterized by even 19Department of Molecular,[356_TD$IF] Cellular distribution of microtubules all over the forming cell plate area. and Developmental Biology, University of Colorado, UCB 347, Boulder, CO Distal phragmoplast Regions of the phragmoplast that face the daughter nuclei. The 80309-0347, USA zone microtubule minus ends are gathered in this zone. 20Department of Plant Biotechnology Division site Region at the cortex defined by CDZ during prophase and cell plate and Bioinformatics, Ghent University, fusion