Recent Topics Posters
Zhang, Yi , Wasteneys, Geoffrey .
Exploiting the handedness of root twisting to map MOR1ís interaction with tubulin in the control of microtubule dynamics.
The twisting of plant organs controls a variety of tropisms including the twining of vines, the wrapping of tendrils around branches and root circumnutation. In recent years, numerous mutants of Arabidopsis thaliana have been identified that display distinct handedness organ twisting. Almost invariably, these mutants have altered microtubule organization and the genes targeted either encode the tubulin protein subunits of microtubules or microtubule-associated proteins (MAPs). The mechanistic basis for twisting or its handedness remains unclear. We are exploiting this intriguing phenomenon to understand at the molecular level how the plant member of the highly conserved MAP215/Dis1 family, interacts with to control microtubule polymerization dynamics. MOR1 has five TOG (Tumor Over-expressed Gene) domains located at the N-terminus, each of which has a core of 6 α-helix-turn-α-helix motifs known as HEAT repeats (HRs) that are stacked side by side to form a flat, paddle-like shape. Two temperature-sensitive mutant alleles of MOR1, mor1-1L174F and mor1-2E195K, suppress microtubule dynamics and cause left-handed twisting organs at restrictive temperature. Both mutations substitute conserved amino acids in the fifth HR (HR5) of the first TOG domain. Previous genetic analysis identified two point mutations in HR5 of the yeast Stu2 homologue of MOR1 that suppress a cold-sensitive β-tubulin mutation, suggesting that the HR5 is critical for the binding of Stu2 to tubulin. From this knowledge, we are undertaking a genetic strategy to map the MOR1-tubulin interaction sites by crossing the left-handed twisting mor1 alleles with a collection of right-handed twisting tubulin mutants. Despite the recessive nature of the mor1 alleles, some combinations generate constitutive left-handed twisting phenotypes in the F1, and in the F2 generation, seedling lethality. These synthetic phenotypes provide a key to identifying the mechanism by which the MOR1 acts as a processive polymerase to control microtubule dynamics during plant growth and development.
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Geoffrey Wasteneys Homepage
1 - University of British Columbia, Department of Botany, 6270 University Blvd., Vancouver, BC, V6T 1Z4, Canada
Presentation Type: Recent Topics Poster
Location: Ball Room & Party Room/SUB
Date: Monday, July 28th, 2008
Time: 12:30 PM