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Auxin and cytokinin interaction in tomato (Lycopersicon esculentum Mill.)

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dc.contributor.advisor Lomax, Terri L.
dc.creator Coenen, Catharina
dc.date.accessioned 2012-10-04T16:30:14Z
dc.date.available 2012-10-04T16:30:14Z
dc.date.copyright 1996-06-13
dc.date.issued 1996-06-13
dc.identifier.uri http://hdl.handle.net/1957/34114
dc.description Graduation date: 1997 en_US
dc.description.abstract The phytohormones auxin and cytokinin control plant development through a complex network of interactions which include synergistic, additive, and opposite effects whose mechanisms are unknown. The auxin-insensitive diageotropica (dgt) mutant provided a tool to dissect the relationship between auxin- and cytokinin-induced responses in tomato. Morphological, physiological, and molecular data support the proposal that auxin and cytokinins control a common set of developmental processes through separate signal transduction pathways which interact downstream from the DGT gene product. Morphological traits of dgt plants, such as reduced root and shoot growth, reduced leaf complexity, and reduced apical dominance were phenocopied by exogenous cytokinin application to wild-type plants, demonstrating that cytokinins and the DGT-mediated auxin response control a common set of phenotypic characteristics. Because the dgt mutation had no detectable effects on the levels of endogenous cytokinins or on the cytokinin sensitivity of whole plants, cytokinins were hypothesized to cause dgt-like effects on plant development through inhibiting auxin-induced responses. This hypothesis was supported by physiological experiments showing that auxin-induced elongation and ethylene synthesis were inhibited in cytokinin-treated wild-type and in untreated dgt hypocotyls. Differences between the effects of cytokinins and the dgt mutation on auxin responses became apparent at the molecular level. Experiments on the auxin-induced accumulation of transcripts for two ACC-synthase genes and one SAUR gene demonstrated that cytokinin treatment selectively reduced the auxin-induced expression of only one ACC-synthase gene, while the dgt mutation inhibited the auxin-inducibility of all three genes. The effects of the dgt mutation were thus more pleiotropic than the cytokinin effects, suggesting that cytokinins inhibit auxin-responses downstream from the DGT gene product. In vitro culture of dgt hypocotyl explants and calli demonstrated shared or interacting signal transduction pathways for auxin and cytokinin in the stimulation of cell division, and independent pathways for the control of organ regeneration and vascular differentiation. en_US
dc.language.iso en_US en_US
dc.subject.lcsh Auxin en_US
dc.subject.lcsh Cytokinins en_US
dc.subject.lcsh Tomatoes -- Physiology en_US
dc.subject.lcsh Tomatoes -- Development en_US
dc.subject.lcsh Tomatoes -- Growth en_US
dc.title Auxin and cytokinin interaction in tomato (Lycopersicon esculentum Mill.) en_US
dc.type Thesis/Dissertation en_US
dc.degree.name Doctor of Philosophy (Ph. D.) in Botany and Plant Pathology en_US
dc.degree.level Doctoral en_US
dc.degree.discipline Science en_US
dc.degree.grantor Oregon State University en_US
dc.contributor.committeemember Rivin, Carol
dc.contributor.committeemember Armstrong, Don
dc.contributor.committeemember Mok, Machteld
dc.contributor.committeemember Farber, Paul
dc.contributor.committeemember Breen, Patrick
dc.description.digitization File scanned at 300 ppi (Monochrome, 8-bit Grayscale, 24-bit Color) using ScandAll PRO 1.8.1 on a Fi-6670 in PDF format. CVista PdfCompressor 4.0 was used for pdf compression and textual OCR. en_US
dc.description.peerreview no en_us

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