title: Root-specific reduction of cytokinin causes enhanced root growth, drought tolerance, and leaf mineral enrichment in Arabidopsis and tobacco.
abstract: Optimizing root system architecture can overcome yield limitations in crop plants caused by water or nutrient shortages. Classic breeding approaches are difficult because the trait is governed by many genes and is difficult to score. We generated transgenic Arabidopsis thaliana and tobacco (Nicotiana tabacum) plants with enhanced root-specific degradation of the hormone cytokinin, a negative regulator of root growth. These transgenic plants form a larger root system, whereas growth and development of the shoot are similar. Elongation of the primary root, root branching, and root biomass formation were increased by up to 60% in transgenic lines, increasing the root-to-shoot ratio. We thus demonstrated that a single dominant gene could regulate a complex trait, root growth. Moreover, we showed that cytokinin regulates root growth in a largely organ-autonomous fashion that is consistent with its dual role as a hormone with both paracrine and long-distance activities. Transgenic plants had a higher survival rate after severe drought treatment. The accumulation of several elements, including S, P, Mn, Mg, Zn, as well as Cd from a contaminated soil, was significantly increased in shoots. Under conditions of sulfur or magnesium deficiency, leaf chlorophyll content was less affected in transgenic plants, demonstrating the physiological relevance of shoot element accumulation. Our approach might contribute to improve drought tolerance, nutrient efficiency, and nutrient content of crop plants.
authors.affiliation: Institute of Biology/Applied Genetics, Dahlem Centre of Plant Sciences, Freie Universität Berlin, D-14195 Berlin, Germany.
authors.forename: Tomás
authors.initials: T
authors.lastname: Werner
authors.forename: Erika
authors.initials: E
authors.lastname: Nehnevajova
authors.forename: Ireen
authors.initials: I
authors.lastname: Köllmer
authors.forename: Ondrej
authors.initials: O
authors.lastname: Novák
authors.forename: Miroslav
authors.initials: M
authors.lastname: Strnad
authors.forename: Ute
authors.initials: U
authors.lastname: Krämer
authors.forename: Thomas
authors.initials: T
authors.lastname: Schmülling
mesh_terms: D000222:Adaptation, Physiological; D017360:Arabidopsis / Q000378:metabolism*; D003583:Cytokinins / Q000378:metabolism*; D008903:Minerals / Q000378:metabolism*; D018515:Plant Leaves / Q000378:metabolism*; D018517:Plant Roots / Q000254:growth & development / Q000378:metabolism* / Q000502:physiology; D030821:Plants, Genetically Modified; D014026:Nicotiana / Q000378:metabolism*
chemical_list: D003583:Cytokinins; D008903:Minerals