The microtubule-associated protein AtMAP70-5 regulates secondary wall patterning in Arabidopsis wood cells

Curr Biol. 2010 Apr 27;20(8):744-9. doi: 10.1016/j.cub.2010.02.057. Epub 2010 Apr 15.


Xylem tracheary elements (TEs) form hollow, sap-conducting tubes kept open by thickened ribs of secondary cell wall that provide the major structural element in wood. These ribs are enriched with cellulose and lignin, molecules that utilize more atmospheric CO(2) than any other biopolymer on Earth. The thickenings form characteristic patterns (e.g., spiral and pitted) that depend upon the bundling of underlying microtubules [1, 2]. To identify microtubule-associated proteins (MAPs) involved in patterning microtubules, we optimized an in vitro system for triggering single Arabidopsis cells to differentiate synchronously into TEs. From more than 200 microtubule-implicated proteins, AtMAP70-5 was the only MAP upregulated upon, and specific to, TE differentiation. It lines the borders of each microtubule bundle and forms C-shaped "spacers" between adjacent bundles. Manipulating levels of AtMAP70-5 and its binding partner AtMAP70-1 by overexpression or RNA interference (RNAi) silencing shifted the balance between the characteristic patterns. RNAi silencing produced stunted plants with disorganized vascular bundles. In culture, RNAi knockdown caused ribs of secondary cell wall, surrounded by microtubules, to invaginate and fall into the cytoplasm. These results suggest that AtMAP70-5 and AtMAP70-1 are essential for defining where secondary cell wall polymers are applied at the cell cortex in wood-forming cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Arabidopsis / cytology*
  • Arabidopsis / physiology*
  • Arabidopsis Proteins / genetics
  • Arabidopsis Proteins / metabolism*
  • Cell Differentiation / physiology
  • Cell Line
  • Cell Wall / chemistry
  • Cell Wall / metabolism
  • Cell Wall / ultrastructure
  • Gene Expression Regulation, Plant
  • Gene Silencing
  • Microtubule-Associated Proteins / genetics
  • Microtubule-Associated Proteins / metabolism*
  • Microtubules / metabolism
  • Microtubules / ultrastructure
  • Polymers / chemistry
  • Polymers / metabolism
  • RNA Interference
  • Two-Hybrid System Techniques
  • Wood / chemistry
  • Wood / cytology*
  • Xylem / cytology


  • Arabidopsis Proteins
  • MAP70-1 protein, Arabidopsis
  • MAP70-5 protein, Arabidopsis
  • Microtubule-Associated Proteins
  • Polymers