title: Microtubule-associated AIR9 recognizes the cortical division site at preprophase and cell-plate insertion.
abstract: In plants, the preprophase band (PPB) of microtubules marks the cortical site where the cross-wall will fuse with the parental wall during cytokinesis . This band disappears before metaphase, and it is not known how the division plane is "memorized". One idea is that the PPB leaves behind molecules involved in the maturation of the cell plate . Here, we report on the proteomic isolation of a novel 187 kDa microtubule-associated protein, AIR9, conserved in land plants and trypanosomatid parasites. AIR9 decorates cortical microtubules and the PPB but is downregulated during mitosis. AIR9 reappears at the former PPB site precisely when the cortex is contacted by the outwardly growing cytokinetic apparatus. AIR9 then moves inward on the new cross-wall and thus forms a torus. Truncation studies show that formation of the torus requires a repeated domain separate from AIR9's microtubule binding site. Cell plates induced to insert outside the predicted division site do not elicit an AIR9 torus, suggesting that AIR9 recognizes a component of the former PPB. Such misplaced walls remain immature, based on their prolonged staining for the cell-plate polymer callose. We propose that AIR9 may be part of the mechanism ensuring the maturation of those cell plates successfully contacting the "programmed" cortical division site.
authors.affiliation: Department of Cell and Developmental Biology, John Innes Centre, Norwich NR4 7UH, United Kingdom. henrik.buschmann@bbsrc.ac.uk
authors.forename: Henrik
authors.initials: H
authors.lastname: Buschmann
authors.forename: Jordi
authors.initials: J
authors.lastname: Chan
authors.forename: Luis
authors.initials: L
authors.lastname: Sanchez-Pulido
authors.forename: Miguel A
authors.initials: MA
authors.lastname: Andrade-Navarro
authors.forename: John H
authors.initials: JH
authors.lastname: Doonan
authors.forename: Clive W
authors.initials: CW
authors.lastname: Lloyd
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000166:cytology / Q000378:metabolism* / Q000648:ultrastructure; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D002473:Cell Wall / Q000378:metabolism; D019295:Computational Biology; D048749:Cytokinesis / Q000502:physiology*; D015536:Down-Regulation; D008868:Microtubule Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D008869:Microtubule-Associated Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D008870:Microtubules / Q000378:metabolism*; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D040901:Proteomics; D016415:Sequence Alignment
chemical_list: C515034:AIR9 protein, Arabidopsis; D029681:Arabidopsis Proteins; D008868:Microtubule Proteins; D008869:Microtubule-Associated Proteins