The beet armyworm, Spodoptera exigua, has evolved numerous mechanisms to circumvent plant defense responses. One of these mechanisms is believed to involve the activity of labial salivary glucose oxidase (GOX) which, through the production of hydrogen peroxide, interferes with plant induced defenses. The activity of GOX is diet-dependent. The expression of SeGox and another salivary gene, Se1H, are differentially regulated in response to diet (plant or transfer from plant to wheat-germ based artificial diet for 4 hours), but not in response to chemically defined artificial diets varying in protein to digestible carbohydrate ratios. However, GOX enzyme activity is dependent on the nutrient quality of the chemically defined artificial diets. This suggests that nutritional quality controls enzyme activity through post-transcriptional regulation. To simulate natural plant diets, Medicago truncatula plants were grown under ambient (440 ppm) or elevated (880 ppm) carbon dioxide conditions to alter their C:N ratio. When caterpillars were fed these plants, labial salivary GOX activity was undetectable regardless of the plant treatment. Finally, 5' upstream regions of salivary genes Se1H, Se2J and SeGox were amplified to determine potential upstream promoter elements, but were unable to be sequenced due to amplicon contamination. / La chenille de Spodoptera exigua est capable de nourrir sur les plantes malgré ses défenses anti-herbivores, grâce à des enzymes salivaires. Un de ces enzymes salivaires capable de combattre les defenses, glucose oxidase (GOX), est aussi régulé par la diète avec laquelle la chenille se nourrit. Il est donc important d'identifier la réglementation des produits salivaires comme GOX. Ce projet vise à déterminer les tendances de transcription et d'activité enzymatique de trois gènes salivaires (Se1H, Se2J et SeGox) en réponse de différentes diètes. De plus, les régions en amont des gènes salivaires ont tentées être séquencer afin de trouver des promoteurs putatives. Les résultats ont démontré que les trois gènes ne sont pas régulées transcriptionellement, mais que l'activité enzymatique de GOX dépend de la qualité nutritive des diètes. Cependant, les régions en amont des trois gènes n'ont pas pu être séquencé à cause de raisons de contaminations et d'amplification imprécises.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.32295 |
| Date | January 2009 |
| Creators | Afshar, Khashayar |
| Contributors | Jacqueline Bede (Supervisor) |
| 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 | French |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Master of Science (Department of Plant Science) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | Electronically-submitted theses. |
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