@phdthesis{19722,
  abstract     = {As root epidermal cells progress from a phase of elongation to differentiation, their
cortical microtubule (MT) arrays exhibit a transversal-to-longitudinal reorientation. The
hormone cytokinin, a key regulator of root development, facilitates these cytoskeletal
changes. However, the molecular mechanisms underlying hormone-mediated MT
reorientation during root development are still unknown. Here, we find that MT reorientation
in root cells differs from the existing model in hypocotyl cells, as it does not rely on MT plusend rescue. We show that cytokinin facilitates MT array reorganization during cell
differentiation by promoting katanin’s (KTN1) severing activity, and by modulating KTN1’s
association with microtubules. Cytokinin regulates SPIRAL2 (SPR2) in a phosphorylationdependent manner, directing its localization to, and stabilization of, the new MT minus-end
created by katanin-mediated severing at crossovers. Notably, our findings suggest that
dynamic and reversible phosphorylation at S579 of SPR2 is crucial for the proper functioning
of the MT severing machinery. Finally, we identify MAP65-1 and CLASP as additional targets
of cytokinin-dependent phosphoregulation. Cytokinin treatment decreases MT-MAP65-1
association in elongating cells, likely to expose MTs to KTN1-mediated severing, whereas it
increases MT-CLASP association to stabilize the growing plus-end. In this way, cytokinin drives
MT reorganization during cell development by simultaneously modulating several
microtubule-associated proteins. These results reveal key molecular players in hormonemediated cytoskeletal regulation, and highlight protein phosphorylation as a powerful tool
during this process.},
  author       = {Inumella, Syamala},
  isbn         = {978-3-99078-059-6},
  issn         = {2663-337X},
  pages        = {113},
  publisher    = {Institute of Science and Technology Austria},
  title        = {{Molecular mechanisms of microtubule reorganization in elongating root epidermal cells}},
  doi          = {10.15479/AT-ISTA-19722},
  year         = {2025},
}