title: Modulated targeting of GFP-AtMAP65-1 to central spindle microtubules during division.
abstract: AtMAP65-1 bundles cortical microtubules and we examined how this property is regulated during division in time-lapse studies of Arabidopsis suspension cells expressing GFP-AtMAP65-1. Spindle fluorescence is diffuse during metaphase, restored to the central spindle at anaphase and then compacted at the midline during late anaphase/early telophase. However, mutagenesis of the microtubule-associated protein (MAP) consensus Cdk site to a non-phosphorylatable form allows premature decoration of microtubules traversing the central region of the metaphase spindle without affecting the timing of the subsequent compaction. This suggests that mutagenesis does not affect compaction but does affect a phosphorylation/dephosphorylation switch that normally targets AtMAP65-1 to the central spindle at the metaphase/anaphase transition. GFP-AtMAP65-1 continues to label the midline of the early phragmoplast, suggesting a structural continuity with the central spindle - both structures being composed of anti-parallel microtubules. However, once the cytokinetic apparatus expands into a ring the MAP becomes depleted at the midline. Despite this, cytokinesis is not arrested and membrane and callose are deposited at the cell plate. It is concluded that AtMAP65-1 plays a role in the central spindle at anaphase to early cytokinesis but is not essential at the midline of the phragmoplast at later stages.
authors.affiliation: Department of Cell and Developmental Biology, John Innes Centre, Norwich NR4 7UH, UK.
authors.forename: Guojie
authors.initials: G
authors.lastname: Mao
authors.forename: Jordi
authors.initials: J
authors.lastname: Chan
authors.forename: Grant
authors.initials: G
authors.lastname: Calder
authors.forename: John H
authors.initials: JH
authors.lastname: Doonan
authors.forename: Clive W
authors.initials: CW
authors.lastname: Lloyd
mesh_terms: D017360:Arabidopsis / Q000166:cytology* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000378:metabolism*; D002453:Cell Cycle / Q000502:physiology*; D002478:Cells, Cultured; D048749:Cytokinesis / Q000502:physiology; D018506:Gene Expression Regulation, Plant; D049452:Green Fluorescent Proteins; D007399:Interphase / Q000502:physiology; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D008870:Microtubules / Q000502:physiology*; D008938:Mitosis / Q000502:physiology; D016297:Mutagenesis, Site-Directed; D010766:Phosphorylation; D008941:Spindle Apparatus / Q000502:physiology*
chemical_list: D029681:Arabidopsis Proteins; C492901:MAP65-1 protein, Arabidopsis; D008869:Microtubule-Associated Proteins; D049452:Green Fluorescent Proteins