title: Arabidopsis TANGLED identifies the division plane throughout mitosis and cytokinesis.
abstract: BACKGROUND
  In premitotic plant cells, the future division plane is predicted by a cortical ring of microtubules and F-actin called the preprophase band (PPB). The PPB persists throughout prophase, but is disassembled upon nuclear-envelope breakdown as the mitotic spindle forms. Following nuclear division, a cytokinetic phragmoplast forms between the daughter nuclei and expands laterally to attach the new cell wall at the former PPB site. A variety of observations suggest that expanding phragmoplasts are actively guided to the former PPB site, but little is known about how plant cells "remember" this site after PPB disassembly.
  
  
  RESULTS
  In premitotic plant cells, Arabidopsis TANGLED fused to YFP (AtTAN::YFP) colocalizes at the future division plane with PPBs. Strikingly, cortical AtTAN::YFP rings persist after PPB disassembly, marking the division plane throughout mitosis and cytokinesis. The AtTAN::YFP ring is relatively broad during preprophase/prophase and mitosis; narrows to become a sharper, more punctate ring during cytokinesis; and then rapidly disassembles upon completion of cytokinesis. The initial recruitment of AtTAN::YFP to the division plane requires microtubules and the kinesins POK1 and POK2, but subsequent maintenance of AtTAN::YFP rings appears to be microtubule independent. Consistent with the localization data, analysis of Arabidopsis tan mutants shows that AtTAN plays a role in guidance of expanding phragmoplasts to the former PPB site.
  
  
  CONCLUSIONS
  AtTAN is implicated as a component of a cortical guidance cue that remains behind when the PPB is disassembled and directs the expanding phragmoplast to the former PPB site during cytokinesis.
authors.affiliation: Section of Cell and Developmental Biology, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093-0116, USA.
authors.forename: Keely L
authors.initials: KL
authors.lastname: Walker
authors.forename: Sabine
authors.initials: S
authors.lastname: Müller
authors.forename: Dorianne
authors.initials: D
authors.lastname: Moss
authors.forename: David W
authors.initials: DW
authors.lastname: Ehrhardt
authors.forename: Laurie G
authors.initials: LG
authors.lastname: Smith
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000032:analysis / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000032:analysis / Q000378:metabolism*; D048749:Cytokinesis; D016547:Kinesins / Q000378:metabolism; D018519:Meristem / Q000166:cytology / Q000378:metabolism; D008870:Microtubules / Q000737:chemistry; D008938:Mitosis; D008969:Molecular Sequence Data; D030821:Plants, Genetically Modified; D011993:Recombinant Fusion Proteins / Q000032:analysis / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D018797:Cell Cycle Proteins; D011993:Recombinant Fusion Proteins; C525946:TANGLED protein, Arabidopsis; C511453:POK1 protein, Arabidopsis; C511454:POK2 protein, Arabidopsis; D016547:Kinesins