Auxins are plant hormones involved in virtually all aspects of plant life. Despite long-term commercial and horticultural use of the auxin Indole-3-Butyric Acid (IBA), a full recognition of its natural occurrence in plants was made only recently. I have used multiple approaches to dissect the role of IBA in Arabidopsis thaliana. This thesis includes the first characterization of a mutant with an altered response to IBA that retains wild-type sensitivity to Indole-3-Acetic Acid (IAA), the most studied endogenous auxin. This mutant, named resistant to IBA ( rib1), has modified root architecture and gravitropism and is resistant to auxin transport inhibitors. As these phenotypes are reminiscent of those of characterized auxin transport mutants, movement of IAA and IBA was studied in wild-type and mutant plants. IBA is transported in seedlings in three distinct flows, like IAA, and this transport is saturable, indicating it is carrier mediated. However, unlike IAA, IBA is not polarly transported in inflorescence axes, and IBA transport is not sensitive to IAA transport inhibitors. These results suggest IAA and IBA transport could be mediated or regulated by different mechanisms. In rib1 seedlings, all flows of IBA transport are modified, while IAA transport levels are unchanged. Modifications in IBA transport match phenotypic differences between rib1 and wild-type, and analyses of the physiological effects of IBA also suggest IBA has a role in defining wild-type seedling morphology in Arabidopsis. Though IAA transport levels are not changed in rib1, one flow of IAA transport is rendered insensitive to IAA transport inhibitors, perhaps revealing cross-talk between IAA and IBA transport regulation. Additionally, double mutant analyses reveal that IAA transport and response mutants can suppress some phenotypes of rib1, and some mutant combinations produce novel phenotypes, further suggesting cross-talk between IBA and IAA transport and response p
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.84312 |
| Date | January 2004 |
| Creators | Poupart, Julie |
| Contributors | Waddell, Candace S. (advisor), Lasko, Paul (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Biology.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 002150392, proquestno: AAINQ98352, Theses scanned by UMI/ProQuest. |
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