title: Regulation of plant growth by cytokinin.
abstract: Cytokinins are a class of plant-specific hormones that play a central role during the cell cycle and influence numerous developmental programs. Because of the lack of biosynthetic and signaling mutants, the regulatory roles of cytokinins are not well understood. We genetically engineered cytokinin oxidase expression in transgenic tobacco plants to reduce their endogenous cytokinin content. Cytokinin-deficient plants developed stunted shoots with smaller apical meristems. The plastochrone was prolonged, and leaf cell production was only 3-4% that of wild type, indicating an absolute requirement of cytokinins for leaf growth. In contrast, root meristems of transgenic plants were enlarged and gave rise to faster growing and more branched roots. These results suggest that cytokinins are an important regulatory factor of plant meristem activity and morphogenesis, with opposing roles in shoots and roots.
authors.affiliation: Centre for Plant Molecular Biology (ZMBP)/Allgemeine Genetik, Universität Tübingen, Auf der Morgenstelle 28, D-72076 Tübingen, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Werner
authors.forename: V
authors.initials: V
authors.lastname: Motyka
authors.forename: M
authors.initials: M
authors.lastname: Strnad
authors.forename: T
authors.initials: T
authors.lastname: Schmülling
mesh_terms: D003583:Cytokinins / Q000235:genetics / Q000502:physiology*; D017343:Genes, Plant; D018519:Meristem / Q000254:growth & development; D008954:Models, Biological; D010088:Oxidoreductases / Q000235:genetics / Q000502:physiology; D010641:Phenotype; D018517:Plant Roots / Q000254:growth & development; D018520:Plant Shoots / Q000254:growth & development; D030821:Plants, Genetically Modified; D010947:Plants, Toxic; D014026:Nicotiana / Q000235:genetics / Q000254:growth & development* / Q000502:physiology
chemical_list: D003583:Cytokinins; D010088:Oxidoreductases; C019984:cytokinin oxidase