title: Ectopic expression of an activated RAC in Arabidopsis disrupts membrane cycling.
abstract: Rho GTPases regulate the actin cytoskeleton, exocytosis, endocytosis, and other signaling cascades. Rhos are subdivided into four subfamilies designated Rho, Racs, Cdc42, and a plant-specific group designated RACs/Rops. This research demonstrates that ectopic expression of a constitutive active Arabidopsis RAC, AtRAC10, disrupts actin cytoskeleton organization and membrane cycling. We created transgenic plants expressing either wild-type or constitutive active AtRAC10 fused to the green fluorescent protein. The activated AtRAC10 induced deformation of root hairs and leaf epidermal cells and was primarily localized in Triton X-100-insoluble fractions of the plasma membrane. Actin cytoskeleton reorganization was revealed by creating double transgenic plants expressing activated AtRAC10 and the actin marker YFP-Talin. Plants were further analyzed by membrane staining with N-[3-triethylammoniumpropyl]-4-[p-diethylaminophenylhexatrienyl] pyridinium dibromide (FM4-64) under different treatments, including the protein trafficking inhibitor brefeldin A or the actin-depolymeryzing agents latrunculin-B (Lat-B) and cytochalasin-D (CD). After drug treatments, activated AtRAC10 did not accumulate in brefeldin A compartments, but rather reduced their number and colocalized with FM4-64-labeled membranes in large intracellular vesicles. Furthermore, endocytosis was compromised in root hairs of activated AtRAC10 transgenic plants. FM4-64 was endocytosed in nontransgenic root hairs treated with the actin-stabilizing drug jasplakinolide. These findings suggest complex regulation of membrane cycling by plant RACs.
authors.affiliation: Department of Plant Sciences, Tel Aviv University, Israel.
authors.forename: Daria
authors.initials: D
authors.lastname: Bloch
authors.forename: Meirav
authors.initials: M
authors.lastname: Lavy
authors.forename: Yael
authors.initials: Y
authors.lastname: Efrat
authors.forename: Idan
authors.initials: I
authors.lastname: Efroni
authors.forename: Keren
authors.initials: K
authors.lastname: Bracha-Drori
authors.forename: Mohamad
authors.initials: M
authors.lastname: Abu-Abied
authors.forename: Einat
authors.initials: E
authors.lastname: Sadot
authors.forename: Shaul
authors.initials: S
authors.lastname: Yalovsky
mesh_terms: D000199:Actins / Q000378:metabolism; D017360:Arabidopsis / Q000166:cytology* / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism*; D048430:Cell Shape; D022162:Cytoplasmic Vesicles / Q000378:metabolism; D004789:Enzyme Activation; D005089:Exocytosis; D015870:Gene Expression; D018515:Plant Leaves / Q000166:cytology / Q000254:growth & development / Q000378:metabolism; D018517:Plant Roots / Q000166:cytology / Q000254:growth & development / Q000378:metabolism; D030821:Plants, Genetically Modified; D020744:rac GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D000199:Actins; D029681:Arabidopsis Proteins; D020744:rac GTP-Binding Proteins