title: A ROP GTPase signaling pathway controls cortical microtubule ordering and cell expansion in Arabidopsis.
abstract: Cortical microtubules (MTs) participate in the spatial control of cell expansion and division that is required for plant growth and morphogenesis. Well-ordered transverse cortical MTs promote cell elongation and restrict radial cell expansion. The molecular mechanism controlling their ordering is poorly understood. We report the first known signaling pathway that promotes the organization of cortical MTs into parallel arrays oriented perpendicular to the axis of cell elongation in plants. Well-ordered MTs locally restrict cell expansion to promote indentation formation in the jigsaw-puzzle-shaped pavement cells of Arabidopsis leaves. Deleting ROP6, a Rho-family GTPase, randomized cortical MTs and released the localized restriction of cell expansion, whereas ROP6 overexpression enhanced MT ordering, turning the jigsaw-puzzle appearance of cells into a cylindrical shape. ROP6 directly binds and activates MT-associated RIC1 to achieve the MT ordering. The ROP6-RIC1 pathway also affects MT ordering of hypocotyl cells, showing a broad role for this pathway in the spatial regulation of cell expansion.
authors.affiliation: State Key Laboratory of Plant Physiology and Biochemistry, Department of Plant Sciences, College of Biological Sciences, China. yingfu@cau.edu.cn
authors.forename: Ying
authors.initials: Y
authors.lastname: Fu
authors.forename: Tongda
authors.initials: T
authors.lastname: Xu
authors.forename: Lei
authors.initials: L
authors.lastname: Zhu
authors.forename: Mingzhang
authors.initials: M
authors.lastname: Wen
authors.forename: Zhenbiao
authors.initials: Z
authors.lastname: Yang
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000201:enzymology* / Q000648:ultrastructure; D029681:Arabidopsis Proteins / Q000032:analysis / Q000378:metabolism* / Q000502:physiology*; D002455:Cell Division; D049108:Cell Enlargement; D031541:Fluorescence Resonance Energy Transfer; D049452:Green Fluorescent Proteins / Q000032:analysis; D008869:Microtubule-Associated Proteins / Q000032:analysis / Q000378:metabolism* / Q000502:physiology; D008870:Microtubules / Q000378:metabolism* / Q000648:ultrastructure; D020559:Monomeric GTP-Binding Proteins / Q000032:analysis / Q000378:metabolism / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000032:analysis; D015398:Signal Transduction
chemical_list: D029681:Arabidopsis Proteins; D008869:Microtubule-Associated Proteins; C547530:RIC1 protein, Arabidopsis; C518506:ROP6 protein, Arabidopsis; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins; D020559:Monomeric GTP-Binding Proteins