title: Arabidopsis lonely guy (LOG) multiple mutants reveal a central role of the LOG-dependent pathway in cytokinin activation.
abstract: Cytokinins are phytohormones that play key roles in the maintenance of stem cell activity in plants. Although alternative single-step and two-step activation pathways for cytokinin have been proposed, the significance of the single-step pathway which is catalyzed by LONELY GUY (LOG), is not fully understood. We analyzed the metabolic flow of cytokinin activation in Arabidopsis log multiple mutants using stable isotope-labeled tracers and characterized the mutants' morphological and developmental phenotypes. In tracer experiments, cytokinin activation was inhibited most pronouncedly by log7, while the other log mutations had cumulative effects. Although sextuple or lower-order mutants did not show drastic phenotypes in vegetative growth, the log1log2log3log4log5log7log8 septuple T-DNA insertion mutant in which the LOG-dependent pathway is impaired, displayed severe retardation of shoot and root growth with defects in the maintenance of the apical meristems. Detailed observation of the mutants showed that LOG7 was required for the maintenance of shoot apical meristem size. LOG7 was also suggested to play a role for normal primary root growth together with LOG3 and LOG4. These results suggest a dominant role of the single-step activation pathway mediated by LOGs for cytokinin production, and overlapping but differentiated functions of the members of the LOG gene family in growth and development.
authors: RIKEN Plant Science Center, 1-7-22, Suehiro, Tsurumi, Yokohama 230-0045, Japan.
authors: Hiroki
authors: H
authors: Tokunaga
authors: Mikiko
authors: M
authors: Kojima
authors: Takeshi
authors: T
authors: Kuroha
authors: Takashi
authors: T
authors: Ishida
authors: Keiko
authors: K
authors: Sugimoto
authors: Takatoshi
authors: T
authors: Kiba
authors: Hitoshi
authors: H
authors: Sakakibara
mesh_terms: D000619:Aminohydrolases; D017360:Arabidopsis / Q000033:anatomy & histology / Q000201:enzymology / Q000235:genetics / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D003583:Cytokinins / Q000032:analysis / Q000378:metabolism*; D035264:Flowers / Q000033:anatomy & histology / Q000201:enzymology / Q000235:genetics / Q000502:physiology; D005816:Genetic Complementation Test; D018519:Meristem / Q000033:anatomy & histology / Q000201:enzymology / Q000235:genetics / Q000502:physiology; D016254:Mutagenesis, Insertional; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D010641:Phenotype; D010937:Plant Growth Regulators / Q000032:analysis / Q000378:metabolism*; D018515:Plant Leaves / Q000033:anatomy & histology / Q000201:enzymology / Q000235:genetics / Q000502:physiology; D018517:Plant Roots / Q000033:anatomy & histology / Q000201:enzymology / Q000235:genetics / Q000502:physiology; D018520:Plant Shoots / Q000033:anatomy & histology / Q000201:enzymology / Q000235:genetics / Q000502:physiology; D011994:Recombinant Proteins; D036226:Seedlings / Q000033:anatomy & histology / Q000201:enzymology / Q000235:genetics / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology; D013997:Time Factors
chemical_list: D029681:Arabidopsis Proteins; D003583:Cytokinins; D009687:Nuclear Proteins; D010937:Plant Growth Regulators; D011994:Recombinant Proteins; D000619:Aminohydrolases; C000589428:cytokinin riboside 5'-monophosphate phosphoribohydrolase, Arabidopsis