Thesis (M. Sc.)--Carleton University, 2005. / Includes bibliographical references (p. 102-106). Also available in electronic format on the Internet.

In Arabidopsis, the mucilage secretory cells (MSC) of the seed coat produce a pectinaceous mucilage. Very little is known about which genes are involved in the synthesis of pectins. A reverse genetic approach was used to identify genes involved in mucilage synthesis. A publicly available microarray database was screened with expression visualization tools, and was complemented by in-lab microarray experiments between wild type and known MSC mutants to identify candidate cell wall genes highly expressed at the time of mucilage synthesis. Several cell wall genes were also chosen based on their putative functions which would implicate them in mucilage synthesis. Phenotyping of mutant lines obtained for the cell wall candidate genes revealed no abnormal mucilage phentoypes in single or select double mutant lines. These results indicate that significant genetic redundancy exists in cell wall genes and/or the genes studied do not play significant roles in mucilage synthesis.

Thesis (M.Sc.) - Carleton University, 2006. / Includes bibliographical references (p. 119-125). Also available in electronic format on the Internet.

No description available.

N-Acylethanolamines (NAEs) are bioactive acylamides that are present in a wide range of organisms. Because NAE levels in seeds decline during imbibition similar to ABA, a physiological role was predicted for these metabolites in Arabidopsis thaliana seed germination and seedling development. There is also a corresponding increase of AtFAAH (fatty acid amide hydrolase), transcript levels and activity, which metabolizes NAE to ethanolamine and free fatty acids. Based on whole genome microarray studies it was determined that a number of up-regulated genes that were responsive to NAE were also ABA responsive. NAE induced gene expression in these ABA responsive genes without elevating endogenous levels of ABA. It was also determined that many of these NAE/ABA responsive genes were associated with an ABA induced secondary growth arrest, including ABI3. ABI3 is a transcription factor that regulates the transition from embryo to seedling growth, the analysis of transcript levels in NAE treated seedlings revealed a dose dependent, inverse relationship between ABI3 transcript levels and growth, high ABI3 transcript levels were associated with growth inhibition. Similar to ABA, NAE negatively regulated seedling growth within a narrow window of early seedling establishment. When seedlings are exposed to NAE or ABA within the window of sensitivity, the induction of genes normally associated with the ungerminated desiccation tolerant state resumed. The NAE tolerant FAAH overexpressor and the NAE sensitive FAAH knockout both had a NAE/ABA sensitive window similar to the wild type A. thaliana. The abi3-1 ABA insensitive mutant does not undergo growth arrest upon exposure to ABA, but NAE did induce growth arrest when treated within the sensitivity window. This evidence showed that although NAE functions within an ABA dependent pathway, it also functions in an ABA independent signaling pathway. The FAAH overexpressor is tolerant to NAE through its ability to quickly metabolize NAE from the growth media, yet it is hypersensitive to ABA. The FAAH overexpressor also displayed hypersensitivity to GA, which improved its delayed germination in non-stratified seed, while the FAAH knock out showed GA insensitivity. Overall, these results showed that NAE functions as a negative regulator of germinating seed and seedling growth in ABA dependent and independent signaling pathways, and that altered NAE metabolism may interfere with ABA/GA perception in germinating seed.