PT  - JOURNAL ARTICLE
AU  - Jelmer J. Lindeboom
AU  - Masayoshi Nakamura
AU  - Marco Saltini
AU  - Anneke Hibbel
AU  - Ankit Walia
AU  - Tijs Ketelaar
AU  - Anne Mie C. Emons
AU  - John C. Sedbrook
AU  - Viktor Kirik
AU  - Bela M. Mulder
AU  - David W. Ehrhardt
TI  - CLASP promotes microtubule array reorientation by acting as a specific severing rescue factor
AID  - 10.1101/196329
DP  - 2018 Jan 01
TA  - bioRxiv
PG  - 196329
4099  - http://biorxiv.org/content/early/2018/03/07/196329.short
4100  - http://biorxiv.org/content/early/2018/03/07/196329.full
AB  - Eukaryotic cells build microtubule arrays to perform essential cellular functions, including division and morphogenesis. Central to building and reorganizing these cytoskeletal arrays is the creation of new polymers. While nucleation has been the major focus of study for new microtubule generation, severing has been proposed as an alternative mechanism to create new polymers, a possibility recently shown to drive the reorientation of cortical arrays of higher plants in response to blue light perception. An important and unanswered question is how the new plus ends created by severing are stabilized to promote net microtubule generation. Here we identify the conserved protein CLASP as a potent in vivo stabilizer of new plus ends generated by katanin mediated severing in the model plant Arabidopsis. In clasp mutants, the fraction of plus ends rescued after severing was reduced by approximately 4.3 - fold and cortical arrays were defective in their ability to reorient. Using the in vivo measurements of molecular behavior, our computational modeling identifies the specific rescue activity of CLASP at severed ends as the key function of CLASP that allows severing to generate a new microtubule array.