A Novel ROP/RAC effector links cell polarity, root-meristem maintenance, and vesicle trafficking.
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.
Lavy
Meirav
M
Department of Plant Sciences, Tel Aviv University, Tel Aviv 69978, Israel.
Bloch
Daria
D
Hazak
Ora
O
Gutman
Itai
I
Poraty
Limor
L
Sorek
Nadav
N
Sternberg
Hasana
H
Yalovsky
Shaul
S
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*
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