Severs microtubules in vitro in an ATP-dependent manner. Required for oligomerization of functional KTN80-KTN1 complexes that catalyze microtubule severing (PubMed:28978669). This activity may promote rapid reorganization of cellular microtubule arrays. May be required for reorientation of cortical microtubule arrays during cellular elongation. Failure to correctly orient these arrays drastically compromises fiber length, cell wall thickness and mechanical strength. May also be required for the spatial organization of developmental cues within the root. n ATP + n H2O + a microtubule = n ADP + n phosphate + (n+1) alpha/beta tubulin heterodimers. May homooligomerize (PubMed:12571277). Component of KTN80-KTN1 complexes composed of a hexamer of KTN1-KTN80 heterodimers that sense microtubule (MT) geometry to confer precise MT severing (PubMed:28978669). Interacts directly with KTN80.1, KTN80.2, KTN80.3 and KTN80.4 (PubMed:28978669). Can interact with KTN80.1 (PubMed:12571277). May interact with the kinesin related protein KIN14A (PubMed:12571277). Interacts with microtubule polymers (PubMed:12571277). Present in dynamic discrete particles specifically localized to microtubule (MT) crossovers and branching nucleation sites, in a KTN80s-dependent manner. Expressed ubiquitously, including siliques, flowers, leaves, stems and roots. Severe dwarf phenotype, with small and round dark-green rosette leaves as well as wide and short petioles. Belongs to the AAA ATPase family. Katanin p60 subunit A1 subfamily.