Cytokinins are plant hormones that affect the primary growth of shoots and roots. Application of the cytokinin N6-benzylaminopurine (BAP) to the shoot apical meristem of <i>Arabidopsis thaliana Landsberg erecta </i>(L.) Heynh induces aberrant flower development and a significant genetic response, and some of these phenotypes and expression patterns were carried to the next generation. Analysis of altered transcript levels with Affymetrix GeneChips® indicated significant changes in transcript levels of genes associated with shoot meristem activity, circadian rhythms, cytokinin metabolism, two-component systems, stress and defense responses, auxin regulation, ethylene and salicylic acid biosynthesis, and signal transduction. Specific genes were also mined from the data as potentially responsible for the BAP-induced aberrant floral phenotypes, increased floral organ number, buds in axils of sepals, and mosaic floral organs. Of particular note was a decrease in the transcript levels of CLAVATA1 (CLV1), a gene encoding a receptor kinase involved in organ differentiation and maintenance of shoot and floral meristems. Time course analysis by RT-PCR showed a decline and subsequent recovery of transcript levels of CLV1 and a coincident increase in WUSCHEL (WUS) transcript, consistent with the known suppression of WUS by CLV. WUS encodes a homeodomain protein associated with shoot meristem proliferation. The temporal coincidence of an increased floral organ phenotype with changes in transcript levels of CLV1 and WUS suggests that cytokinins regulate flower development by affecting the activity of genes controlling shoot meristem activity. Aberrant floral phenotypes in subsequent non-treated generations suggest epigenetic inheritance of some BAP-altered transcript patterns. Repressed expression of the majority of significant genes in the untreated T1 population suggests a mechanism of gene silencing, such as methylation, was involved in this epigenetic inheritance. Also, transcript levels of time-keeping genes, including CIRCADIAN CLOCK ASSOCIATED 1 / ELONGATED HYPOCOTYL, and associated genes with oscillating expression patterns, such as COLD-RESPONSIVE, were affected by BAP in treated plants and the subsequent generation, suggesting the capacity of cytokinins to affect the phase of the circadian clock. Hormonal regulation of heritably altered diurnal periodicity and environmental responses may provide a developmental and, therefore, evolutionary advantage to plants.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:SSU.etd-09172006-083412 |
| Date | 26 September 2006 |
| Creators | Lindsay, Donna Louise |
| Contributors | Sawhney, Vipen K., Fobert, Pierre R., Cota-Sánchez, J. Hugo, Bonham-Smith, Peta C., Scoles, Graham |
| Publisher | University of Saskatchewan |
| 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 | text |
| Format | application/pdf |
| Source | http://library.usask.ca/theses/available/etd-09172006-083412/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Saskatchewan or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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