title: The Agrobacterium vitis T-6b oncoprotein induces auxin-independent cell expansion in tobacco.
abstract: Among the Agrobacterium T-DNA genes, rolB, rolC, orf13, orf8, lso, 6b and several other genes encode weakly homologous proteins with remarkable effects on plant growth. The 6b oncogene induces tumors and enations. In order to study its properties we have used transgenic tobacco plants that carry a dexamethasone-inducible 6b gene, dex-T-6b. Upon induction, dex-T-6b plants develop a large array of morphological modifications, some of which involve abnormal cell expansion. In the present investigation, dex-T-6b-induced expansion was studied in intact leaves and an in vitro leaf disc system. Although T-6b and indole-3-acetic acid (IAA) both induced expansion and were non-additive, T-6b expression did not increase IAA levels, nor did it induce an IAA-responsive gene. Fusicoccin (FC) is known to stimulate expansion by increasing cell wall plasticity. T-6b- and FC-induced expansion were additive at saturating FC concentrations, indicating that T-6b does not act by a similar mechanism to FC. T-6b expression led to higher leaf osmolality values, in contrast to FC, suggesting that the T-6b gene induces expansion by increasing osmolyte concentrations. Metabolite profiling showed that glucose and fructose played a major role in this increase. We infer that T-6b disrupts the osmoregulatory controls that govern cell expansion during development and wound healing.
authors.affiliation: Department of Cell Biology, Institut de Biologie Moléculaire des Plantes, Rue du Général Zimmer 12, 67084 Strasbourg, France.
authors.forename: Bernadette
authors.initials: B
authors.lastname: Clément
authors.forename: Stephan
authors.initials: S
authors.lastname: Pollmann
authors.forename: Elmar
authors.initials: E
authors.lastname: Weiler
authors.forename: Ewa
authors.initials: E
authors.lastname: Urbanczyk-Wochniak
authors.forename: Léon
authors.initials: L
authors.lastname: Otten
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology*; D049108:Cell Enlargement / Q000187:drug effects; D004269:DNA, Bacterial / Q000235:genetics; D003907:Dexamethasone / Q000494:pharmacology; D005632:Fructose / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D006027:Glycosides / Q000494:pharmacology; D007210:Indoleacetic Acids / Q000494:pharmacology; D015513:Oncogene Proteins / Q000235:genetics / Q000502:physiology*; D010937:Plant Growth Regulators / Q000494:pharmacology; D018515:Plant Leaves / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D011188:Potassium / Q000378:metabolism; D012231:Rhizobium / Q000235:genetics*; D014026:Nicotiana / Q000166:cytology* / Q000254:growth & development / Q000382:microbiology*
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D006027:Glycosides; D007210:Indoleacetic Acids; D015513:Oncogene Proteins; D010937:Plant Growth Regulators; C036483:T-DNA; C007808:fusicoccin; D005632:Fructose; C030737:indoleacetic acid; D003907:Dexamethasone; D005947:Glucose; D011188:Potassium