title: A Novel ROP/RAC effector links cell polarity, root-meristem maintenance, and vesicle trafficking.
abstract: ROP/RAC GTPases are master regulators of cell polarity in plants, implicated in the regulation of diverse signaling cascades including cytoskeleton organization, vesicle trafficking, and Ca(2+) gradients [1-8]. The involvement of ROPs in differentiation processes is yet unknown. Here we show the identification of a novel ROP/RAC effector, designated interactor of constitutive active ROPs 1 (ICR1), that interacts with GTP-bound ROPs. ICR1 knockdown or silencing leads to cell deformation and loss of root stem-cell population. Ectopic expression of ICR1 phenocopies activated ROPs, inducing cell deformation of leaf-epidermis-pavement and root-hair cells [3, 5, 6, 9]. ICR1 is comprised of coiled-coil domains and forms complexes with itself and the exocyst vesicle-tethering complex subunit SEC3 [10-13]. The ICR1-SEC3 complexes can interact with ROPs in vivo. Plants overexpressing a ROP- and SEC3-noninteracting ICR1 mutant have a wild-type phenotype. Taken together, our results show that ICR1 is a scaffold-mediating formation of protein complexes that are required for cell polarity, linking ROP/RAC GTPases with vesicle trafficking and differentiation.
authors.affiliation: Department of Plant Sciences, Tel Aviv University, Tel Aviv 69978, Israel.
authors.forename: Meirav
authors.initials: M
authors.lastname: Lavy
authors.forename: Daria
authors.initials: D
authors.lastname: Bloch
authors.forename: Ora
authors.initials: O
authors.lastname: Hazak
authors.forename: Itai
authors.initials: I
authors.lastname: Gutman
authors.forename: Limor
authors.initials: L
authors.lastname: Poraty
authors.forename: Nadav
authors.initials: N
authors.lastname: Sorek
authors.forename: Hasana
authors.initials: H
authors.lastname: Sternberg
authors.forename: Shaul
authors.initials: S
authors.lastname: Yalovsky
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D001692:Biological Transport; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D002454:Cell Differentiation; D016764:Cell Polarity; D019204:GTP-Binding Proteins / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000032:analysis; D018519:Meristem / Q000166:cytology / Q000378:metabolism*; D009154:Mutation; D010641:Phenotype; D018517:Plant Roots / Q000166:cytology / Q000378:metabolism; D022161:Transport Vesicles / Q000502:physiology*; D020744:rac GTP-Binding Proteins / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D002352:Carrier Proteins; C522443:ICR1 protein, Arabidopsis; D049452:Green Fluorescent Proteins; D019204:GTP-Binding Proteins; C501663:ROP1 protein, Arabidopsis; D020744:rac GTP-Binding Proteins