The Arabidopsis CLASP gene encodes a microtubule-associated protein involved in cell expansion and division

Plant Cell. 2007 Sep;19(9):2763-75. doi: 10.1105/tpc.107.053777. Epub 2007 Sep 14.


Controlling microtubule dynamics and spatial organization is a fundamental requirement of eukaryotic cell function. Members of the ORBIT/MAST/CLASP family of microtubule-associated proteins associate with the plus ends of microtubules, where they promote the addition of tubulin subunits into attached kinetochore fibers during mitosis and stabilize microtubules in the vicinity of the plasma membrane during interphase. To date, nothing is known about their function in plants. Here, we show that the Arabidopsis thaliana CLASP protein is a microtubule-associated protein that is involved in both cell division and cell expansion. Green fluorescent protein-CLASP localizes along the full length of microtubules and shows enrichment at growing plus ends. Our analysis suggests that CLASP promotes microtubule stability. clasp-1 T-DNA insertion mutants are hypersensitive to microtubule-destabilizing drugs and exhibit more sparsely populated, yet well ordered, root cortical microtubule arrays. Overexpression of CLASP promotes microtubule bundles that are resistant to depolymerization with oryzalin. Furthermore, clasp-1 mutants have aberrant microtubule preprophase bands, mitotic spindles, and phragmoplasts, indicating a role for At CLASP in stabilizing mitotic arrays. clasp-1 plants are dwarf, have significantly reduced cell numbers in the root division zone, and have defects in directional cell expansion. We discuss possible mechanisms of CLASP function in higher plants.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis / cytology*
  • Arabidopsis / drug effects
  • Arabidopsis / genetics
  • Arabidopsis / metabolism*
  • Arabidopsis Proteins / chemistry
  • Arabidopsis Proteins / genetics*
  • Cell Division* / drug effects
  • Cell Proliferation / drug effects
  • Cell Size / drug effects
  • Cytokinesis / drug effects
  • Dinitrobenzenes / pharmacology
  • Gene Expression Regulation, Plant / drug effects
  • Green Fluorescent Proteins / metabolism
  • Interphase / drug effects
  • Microtubule-Associated Proteins / chemistry
  • Microtubule-Associated Proteins / genetics*
  • Microtubules / drug effects
  • Microtubules / metabolism
  • Mitosis / drug effects
  • Mutation / genetics
  • Phylogeny
  • Plant Epidermis / cytology
  • Plant Epidermis / drug effects
  • Plant Epidermis / ultrastructure
  • Plant Leaves / cytology
  • Plant Leaves / drug effects
  • Plant Leaves / ultrastructure
  • Plant Roots / cytology
  • Plant Roots / drug effects
  • Plant Roots / growth & development
  • Protein Structure, Tertiary
  • Recombinant Fusion Proteins / metabolism
  • Sulfanilamides / pharmacology


  • Arabidopsis Proteins
  • Dinitrobenzenes
  • Microtubule-Associated Proteins
  • Recombinant Fusion Proteins
  • Sulfanilamides
  • Green Fluorescent Proteins
  • oryzalin