The model plant Arabidopsis thaliana has been very successful thus far as a tool for understanding and studying the genetics of plant development. Analysis of its sequenced genome revealed the occurrence of duplicated chromosome blocks, resulting in duplicated genes. Duplicated genes, high in sequence and/or structure similarity, form gene families. One such family, of BRX-like genes, is presented in this thesis. All members contain a characteristic "BRX" domain that is required for BRX activity in planta. BRX (BREVIS RADIX), is a novel regulator of root growth in Arabidopsis. However, analyses of Arabidopsis single and double mutants with other gene family members, suggests that BRX is the only member with a dominating role in root development. Interestingly, BRXL1, although having BRX activity in the root, does not act redundantly with BRX in vivo, presumably because it is expressed at much lower levels than BRX. These two gene family members demonstrate the uncommon phenomenon of unequal genetic redundancy in plants. Another gene family member, BRXL4, although non-redundant with regards to BRX activity in the root, did display novel shoot-related phenotypes when over-expressed. In these lines the lateral shoots and hypocotyls showed increased Gravitropic Set-Point Angles resulting in the downward growth of the adult lateral shoots and a wide range of growth directions in the hypocotyls. Over-expression lines of BRXL4 also displayed seedling agravitropism. Auxin-induced transcription as monitored by the DR5::GUS reporter, is altered in these lines compared to wild-type. Additionally, hypocotyl curvature, stem bending and amyloplast localization profiles in response to a change in gravity vector, are also altered in these over-expression lines and in the brxl4 mutant compared to wild-type.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.102962 |
| Date | January 2006 |
| Creators | Briggs, Georgette C. |
| 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 | © Georgette C. Briggs, 2006 |
| Relation | alephsysno: 002600278, proquestno: AAINR32156, Theses scanned by UMI/ProQuest. |
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