title: Rho GTPase signaling activates microtubule severing to promote microtubule ordering in Arabidopsis.
abstract: BACKGROUND
  Ordered cortical microtubule (MT) arrays play a critical role in the spatial control of cell division and expansion and are essential for plant growth, morphogenesis, and development. Various developmental, hormonal, and mechanical signals and a large number of MT-associated proteins are known to impact cortical MT organization, but the underlying mechanisms remain poorly understood. Our previous studies show that auxin signaling, which is mediated by the ROP6 Rho GTPase and its effector RIC1, promotes the ordering of cortical MTs in pavement cells, but it is unknown how RIC1 controls the organization of cortical MTs into well-ordered arrays.
  
  
  RESULTS
  Our genetic screens identified the conserved MT-severing protein katanin (KTN1) as a downstream component of the ROP6-RIC1 signaling pathway leading to well-ordered arrangement of cortical MTs. KTN1 and RIC1 proteins displayed overlapping localization. In vivo and in vitro studies showed that RIC1 physically interacts with and promotes the MT-severing activity of KTN1. Live-cell imaging reveals a role for RIC1 in promoting detachment of branched MTs that is known to rely on KTN1.
  
  
  CONCLUSIONS
  We have demonstrated that a Rho GTPase signaling pathway regulates katanin-mediated MT severing in plant cells and uncovered an explicit regulatory mechanism underpinning the alignment and ordering of cortical MTs in plants. Our findings provide new insights into regulatory mechanisms underlying growth stimuli such as auxin promote the organization of cortical MTs into parallel arrays in plants.
authors: State Key Laboratory of Plant Physiology and Biochemistry, Department of Plant Sciences, College of Biological Sciences, China Agricultural University, Beijing 100193, China.
authors: Deshu
authors: D
authors: Lin
authors: Lingyan
authors: L
authors: Cao
authors: Zhenzhen
authors: Z
authors: Zhou
authors: Lei
authors: L
authors: Zhu
authors: David
authors: D
authors: Ehrhardt
authors: Zhenbiao
authors: Z
authors: Yang
authors: Ying
authors: Y
authors: Fu
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D007210:Indoleacetic Acids / Q000378:metabolism; D000074201:Katanin; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D008870:Microtubules / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D020559:Monomeric GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D015398:Signal Transduction; D020741:rho GTP-Binding Proteins / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D007210:Indoleacetic Acids; D008869:Microtubule-Associated Proteins; C547530:RIC1 protein, Arabidopsis; C518506:ROP6 protein, Arabidopsis; D000251:Adenosine Triphosphatases; D020559:Monomeric GTP-Binding Proteins; D020741:rho GTP-Binding Proteins; C436244:KTN1 protein, Arabidopsis; D000074201:Katanin