Microtubule plus-ends reveal essential links between intracellular polarization and localized modulation of endocytosis during division-plane establishment in plant cells
1 Section of Molecular Cytology, Swammerdam Institute for Life Sciences, University of Amsterdam, Kruislaan 316, 1098 SM Amsterdam, The Netherlands
2 Department of Plant Agriculture, Molecular Cell Biology Laboratory, University of Guelph, Guelph, ON, N1G 2W1, Canada
3 Botanical Institute III, University of Köln, Gyrhofstrasse 15, Köln, 50931, Germany
4 Centre for Molecular Biology of Plants, University of Tübingen, Auf der Morgenstelle 3, 72076 Tübingen, Germany
BMC Biology 2005, 3:11 doi:10.1186/1741-7007-3-11Published: 14 April 2005
A key event in plant morphogenesis is the establishment of a division plane. A plant-specific microtubular preprophase band (PPB) accurately predicts the line of cell division, whereas the phragmoplast, another plant-specific array, executes cell division by maintaining this predicted line. Although establishment of these specific arrays apparently involves intracellular repolarization events that focus cellular resources to a division site, it still remains unclear how microtubules position the cell division planes. Here we study GFP-AtEB1 decorated microtubule plus-ends to dissect events at the division plane.
Early mitotic events included guided growth of endoplasmic microtubules (EMTs) towards the PPB site and their coincident localization with endocytic vesicles. Consequently, an endosomal belt lay in close proximity to the microtubular PPB at its maturation and was maintained during spindle formation. During cytokinesis, EMTs radiated from the former spindle poles in a geometrical conformation correlating with cell-plate navigation and tilt-correction. Naphthylphtalamic acid (NPA), an inhibitor of polar auxin efflux, caused abnormal PPBs and shifted division planes.
Our observations reveal a spatio-temporal link between microtubules and intracellular polarization essential for localized endocytosis and precise establishment of the division plane in plants. Additionally, they implicate the growth regulator, auxin, in this important cellular event.