The Ehrhardt and Hashimoto groups met this challenge by tagging a component of these complexes, known as nucleating complexes, with multiple copies of a fluorescent protein derived from jellyfish. When introduced into plant cells and visualized with highly sensitive spinning disk confocal microscopy, this tagged protein permitted the researchers to observe what happens as the microtubule array is being built.
Ehrhardt continued: "In centrosomal arrays, these nucleating complexes are recruited to the centrosome, where they give rise to a star-shaped array centered near the nucleus. By contrast, in the cells we studied these complexes were distributed at the cell membrane and were primarily located along the sides of other microtubules, an association that was correlated with their activity. So, microtubules appear to be important for locating and regulating their own formation proteins. In addition, daughter microtubules were created either at a distinct angle to the mother polymer, or in parallel to it. This choice of angle may play a role in either creating new organizational states or maintaining an existing one."
The investigators observed that formation complexes frequently did not remain in place after creating new microtubules, but often left, presumably to go through a new cycle of microtubule creation at a new location. The scientists hypothesized that liberation of the complexes from mother microtubules might be related to the mechanism of daughter microtubule detachment from origination sites.<
|Contact: David Ehrhardt|