title: Auxin regulation of cytokinin biosynthesis in Arabidopsis thaliana: a factor of potential importance for auxin-cytokinin-regulated development.
abstract: One of the most long-lived models in plant science is the belief that the long-distance transport and ratio of two plant hormones, auxin and cytokinin, at the site of action control major developmental events such as apical dominance. We have used in vivo deuterium labeling and mass spectrometry to investigate the dynamics of homeostatic cross talk between the two plant hormones. Interestingly, auxin mediates a very rapid negative control of the cytokinin pool by mainly suppressing the biosynthesis via the isopentenyladenosine-5'-monophosphate-independent pathway. In contrast, the effect of cytokinin overproduction on the entire auxin pool in the plant was slower, indicating that this most likely is mediated through altered development. In addition, we were able to confirm that the lateral root meristems are likely to be the main sites of isopentenyladenosine-5'-monophosphate-dependent cytokinin synthesis, and that the aerial tissue of the plant surprisingly also was a significant source of cytokinin biosynthesis. Our demonstration of shoot-localized synthesis, together with data demonstrating that auxin imposes a very rapid regulation of cytokinin biosynthesis, illustrates that the two hormones can interact also on the metabolic level in controlling plant development, and that the aerial part of the plant has the capacity to synthesize its own cytokinin independent of long-range transport from the root system.
authors.affiliation: Umeå Plant Science Centre, Forest Genetics and Plant Physiology, Swedish University of Agricultural Sciences, 901 83 Umeå, Sweden.
authors.forename: Anders
authors.initials: A
authors.lastname: Nordström
authors.forename: Petr
authors.initials: P
authors.lastname: Tarkowski
authors.forename: Danuse
authors.initials: D
authors.lastname: Tarkowska
authors.forename: Rikke
authors.initials: R
authors.lastname: Norbaek
authors.forename: Crister
authors.initials: C
authors.lastname: Astot
authors.forename: Karel
authors.initials: K
authors.lastname: Dolezal
authors.forename: Göran
authors.initials: G
authors.lastname: Sandberg
mesh_terms: D000249:Adenosine Monophosphate / Q000031:analogs & derivatives* / Q000096:biosynthesis / Q000378:metabolism; D017360:Arabidopsis / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D003583:Cytokinins / Q000096:biosynthesis* / Q000378:metabolism; D007210:Indoleacetic Acids / Q000378:metabolism / Q000494:pharmacology*; D007541:Isopentenyladenosine / Q000031:analogs & derivatives / Q000096:biosynthesis / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D035261:Plant Components, Aerial / Q000187:drug effects / Q000378:metabolism; D018517:Plant Roots / Q000187:drug effects / Q000378:metabolism; D013997:Time Factors
chemical_list: D003583:Cytokinins; D007210:Indoleacetic Acids; C467060:zeatin riboside 5'-phosphate; C008196:N(6)-(delta(2)-isopentenyl)adenosine 5'-monophosphate; D000249:Adenosine Monophosphate; D007541:Isopentenyladenosine