- John C. Sedbrook (1)
- Anneke Hibbel (1)
- Jelmer J. Lindeboom(older publications) (1)
- Jelmer J. Lindeboom (1)
- Tijs Ketelaar (1)
- Viktor Kirik (1)
- Bela M. Mulder (2)
- Anne Mie C. Emons (1)
- Masayoshi Nakamura (2)
- Marco Saltini(older publications) (1)
- Marco Saltini (1)
- David W. Ehrhardt (2)
- Ankit Walia (1)
CLASP stabilization of plus ends created by severing promotes microtubule creation and reorientation
Lindeboom, Jelmer J. ; Nakamura, Masayoshi ; Saltini, Marco ; Hibbel, Anneke ; Walia, Ankit ; Ketelaar, Tijs ; Emons, Anne Mie C. ; Sedbrook, John C. ; Kirik, Viktor ; Mulder, Bela M. ; Ehrhardt, David W. - \ 2019
Journal of Cell Biology 218 (2019). - ISSN 0021-9525 - p. 190 - 205.
Central to the building and reorganizing cytoskeletal arrays is creation of new polymers. Although nucleation has been the major focus of study for microtubule generation, severing has been proposed as an alternative mechanism to create new polymers, a mechanism recently shown to drive the reorientation of cortical arrays of higher plants in response to blue light perception. Severing produces new plus ends behind the stabilizing GTP-cap. An important and unanswered question is how these ends are stabilized in vivo to promote net microtubule generation. Here we identify the conserved protein CLASP as a potent stabilizer of new plus ends created by katanin severing in plant cells. Clasp mutants are defective in cortical array reorientation. In these mutants, both rescue of shrinking plus ends and the stabilization of plus ends immediately after severing are reduced. Computational modeling reveals that it is the specific stabilization of severed ends that best explains CLASP's function in promoting microtubule amplification by severing and array reorientation.
SPR2 protects minus ends to promote severing and reorientation of plant cortical microtubule arrays
Nakamura, Masayoshi ; Lindeboom, Jelmer J. ; Saltini, Marco ; Mulder, Bela M. ; Ehrhardt, David W. - \ 2018
Journal of Cell Biology 217 (2018)3. - ISSN 0021-9525 - p. 915 - 927.
The cortical microtubule arrays of higher plants are organized without centrosomes and feature treadmilling polymers that are dynamic at both ends. The control of polymer end stability is fundamental for the assembly and organization of cytoskeletal arrays, yet relatively little is understood about how microtubule minus ends are controlled in acentrosomal microtubule arrays, and no factors have been identified that act at the treadmilling minus ends in higher plants. Here, we identify Arabidopsis thaliana SPI RAL2 (SPR2) as a protein that tracks minus ends and protects them against subunit loss. SPR2 function is required to facilitate the rapid reorientation of plant cortical arrays as stimulated by light perception, a process that is driven by microtubule severing to create a new population of microtubules. Quantitative live-cell imaging and computer simulations reveal that minus protection by SPR2 acts by an unexpected mechanism to promote the lifetime of potential SPR2 severing sites, increasing the likelihood of severing and thus the rapid amplification of the new microtubule array.