How does MICROTUBULE ORGANIZATION 1 (MOR1) regulate microtubule dynamics in Arabidopsis thaliana?

• Applicant: Dr. Bettina Lechner
• Subject Area: Plant Cell and Developmental Biology
• Term: from 2010 to 2013
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 168000184

All eukaryotic cells depend on dynamic arrays of protein filaments called microtubules (MTs) for intracellular transport, cell shape and division. Rapid rearrangement of MTs requires the activity of microtubuleassociated proteins of the XMAP215/Dis2 family, a highly conserved class of proteins. These proteins promote both MT growth and shrinkage and move processively with the MT ends, thus enabling catalysis of multiple reactions. Like other XMAP215/Dis2 members, the plant homologue MOR1 is predicted to form a long linear molecule with multiple N-terminal TOG domains. Mutant alleles of MOR1 identified in forward genetics screens that cause temperature-dependent loss of MT dynamics, consistently substitute conserved amino acids in only the first TOG domain, suggesting that this N-terminal domain is crucial for polymerase activity. We therefore intend to specifically test the hypothesis that the first TOG domain plays a crucial role in recruitment of free tubulin dimers to the growing plus end of MTs. We will utilize the higher plant model system Arabidopsis thaliana to elucidate the molecular mechanisms that enable XMAP215/Dis2 family proteins to work as processive polymerases. By combining in vitro polymerization assays, single molecule and live cell imaging, we will compare genetically engineered MOR1 constructs carrying specific point mutations and domain deletions. These findings will stimulate new ideas and understanding of a process that is central to eukaryotic cell function.

• DFG Programme: Research Fellowships
• International Connection: Canada
• Host: Professor Dr. Geoffrey O. Wasteneys