title: Shortening of Microtubule Overlap Regions Defines Membrane Delivery Sites during Plant Cytokinesis.
abstract: Different from animal cells that divide by constriction of the cortex inward, cells of land plants divide by initiating a new cell-wall segment from their center. For this, a disk-shaped, membrane-enclosed precursor termed the cell plate is formed that radially expands toward the parental cell wall [1-3]. The synthesis of the plate starts with the fusion of vesicles into a tubulo-vesicular network [4-6]. Vesicles are putatively delivered to the division plane by transport along microtubules of the bipolar phragmoplast network that guides plate assembly [7-9]. How vesicle immobilization and fusion are then locally triggered is unclear. In general, a framework for how the cytoskeleton spatially defines cell-plate formation is lacking. Here we show that membranous material for cell-plate formation initially accumulates along regions of microtubule overlap in the phragmoplast of the moss Physcomitrella patens. Kinesin-4-mediated shortening of these overlaps at the onset of cytokinesis proved to be required to spatially confine membrane accumulation. Without shortening, the wider cell-plate membrane depositions evolved into cell walls that were thick and irregularly shaped. Phragmoplast assembly thus provides a regular lattice of short overlaps on which a new cell-wall segment can be scaffolded. Since similar patterns of overlaps form in central spindles of animal cells, involving the activity of orthologous proteins [10, 11], we anticipate that our results will help uncover universal features underlying membrane-cytoskeleton coordination during cytokinesis.
authors.affiliation: Laboratory of Cell Biology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, the Netherlands; Marine Biological Laboratory, 7 MBL Street, Woods Hole, MA 02543, USA.
authors.forename: Jeroen
authors.initials: J
authors.lastname: de Keijzer
authors.affiliation: Laboratory of Cell Biology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, the Netherlands.
authors.forename: Henk
authors.initials: H
authors.lastname: Kieft
authors.affiliation: Laboratory of Cell Biology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, the Netherlands.
authors.forename: Tijs
authors.initials: T
authors.lastname: Ketelaar
authors.affiliation: Marine Biological Laboratory, 7 MBL Street, Woods Hole, MA 02543, USA; Division of Biological Science, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan.
authors.forename: Gohta
authors.initials: G
authors.lastname: Goshima
authors.affiliation: Laboratory of Cell Biology, Wageningen University, Droevendaalsesteeg 1, 6708 PB Wageningen, the Netherlands; Marine Biological Laboratory, 7 MBL Street, Woods Hole, MA 02543, USA. Electronic address: marcel.janson@wur.nl.
authors.forename: Marcel E
authors.initials: ME
authors.lastname: Janson
mesh_terms: D019068:Bryopsida / Q000502:physiology*; D002473:Cell Wall / Q000502:physiology; D048749:Cytokinesis; D003599:Cytoskeleton / Q000502:physiology*; D016547:Kinesins / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism*; D010940:Plant Proteins / Q000378:metabolism*
chemical_list: D010940:Plant Proteins; D016547:Kinesins
keywords: Physcomitrella patens; cell-plate membrane; division plane; kinesin-4; microtubule overlap; phragmoplast; plant cytokinesis