The shikimate pathway links carbohydrate metabolism to the biosynthesis of the aromatic amino acids and an enormous variety of aromatic compounds with essential functions in all kingdoms of life. Aromatic compounds derived from the plant shikimate pathway have substantial biotechnological value and many are essential to the diet of metazoans whose genomes do not encode shikimate pathway enzymes. Despite its importance to the physiology of plants and human health the regulatory mechanisms of the plant shikimate pathway are not well understood.
Shikimate kinase (SK) genes encode an intermediate step in the shikimate pathway and were previously implicated in regulation of the plant shikimate pathway. The distribution of SK genes in higher plants was resolved using phylogenetic and biochemical methods. The two SK isoforms of Arabidopsis thaliana, AtSK1 and AtSK2, were functionally characterized. AtSK1 expression is induced by heat stress and the recombinant enzyme was shown to form a homodimer which is important for maintaining the stability and activity of the enzyme at elevated temperatures. The crystal structure of AtSK2, the first reported plant SK structure, identified structural features unique to plant SKs which may perform important regulatory functions.
The resolution of bona fide SKs in higher plants led to the discovery of two novel neofunctionalized homologs - Shikimate Kinase-Like 1 (SKL1) and SKL2. These novel genes evolved from SK gene duplicates over 400 million years ago and are found in all major extant angiosperm lineages, suggesting they were important in the development of biological properties required by land plants. The description of albino and variegated skl1 mutants in Arabidopsis thaliana implicate the SKL1 gene product as an important regulator of chloroplast biogenesis. Functional assays were attempted to determine the biochemical function of SKL1 and recombinant constructs of the Arabidopsis thaliana SKL1 protein were crystallized towards structure determination.
The results of this thesis further our understanding of the organization and regulation of the plant shikimate pathway. Furthermore, the discovery of SKL1 may yield important insights into chloroplast biogenesis and function. The evolution of the plant SK superfamily highlights the utility of SKs as scaffolds for functional innovation.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:OTU.1807/29724 |
| Date | 30 August 2011 |
| Creators | Fucile, Geoffrey |
| Contributors | Christendat, Dinesh |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | en_ca |
| Detected Language | English |
| Type | Thesis |
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