title: Diet-specific salivary gene expression and glucose oxidase activity in Spodoptera exigua (Lepidoptera: Noctuidae) larvae.
abstract: Saliva secreted during caterpillar feeding contains enzymes to initiate digestion or detoxify noxious plant compounds. Activity of some salivary enzymes is diet-dependent and may be transcriptionally regulated. In this study, cDNA-amplified fragment length polymorphism was used to identify beet armyworm, Spodoptera exigua Hübner, labial salivary genes that are differentially expressed in response to diet. In addition, SeGOX was sequenced based on homology and characterized to confirm that the transcript encodes a functional enzyme. Three labial salivary transcripts, encoding glucose oxidase (GOX) and two proteins of unknown function (Se1H and Se2J), were expressed in a diet-specific manner. Since diet, particularly the protein to digestible carbohydrate levels and ratio, may affect labial salivary enzyme activity, the influence of nutritional quality on gene expression was determined. Transcript levels of the labial salivary genes Se1H, Se2J and SeGOX increased with dietary carbohydrate levels, regardless of protein concentrations. In contrast GOX enzymatic activity increased with increasing dietary carbohydrates when caterpillars were fed protein-rich diets, but not when caterpillars were fed protein-poor diets. Our results suggest that dietary carbohydrates affect SeGOX, Se1H and Se2J transcription, but dietary protein or amino acid levels affect translational and/or post-translational regulation of the enzyme GOX.
authors.affiliation: Department of Plant Science, McGill University, 21,111 Lakeshore, Ste-Anne-de-Bellevue, Québec, Canada. Khashayar.afshar@mail.mcgill.ca
authors.forename: Khashayar
authors.initials: K
authors.lastname: Afshar
authors.forename: Philippe J
authors.initials: PJ
authors.lastname: Dufresne
authors.forename: Li
authors.initials: L
authors.lastname: Pan
authors.forename: Magali
authors.initials: M
authors.lastname: Merkx-Jacques
authors.forename: Jacqueline C
authors.initials: JC
authors.lastname: Bede
mesh_terms: D054458:Amplified Fragment Length Polymorphism Analysis; D000818:Animals; D004040:Dietary Carbohydrates / Q000378:metabolism*; D004044:Dietary Proteins / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic; D005949:Glucose Oxidase / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D012313:RNA / Q000737:chemistry / Q000235:genetics; D012463:Saliva / Q000201:enzymology* / Q000378:metabolism; D017422:Sequence Analysis, DNA; D018411:Spodoptera / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism
chemical_list: D004040:Dietary Carbohydrates; D004044:Dietary Proteins; D012313:RNA; D005949:Glucose Oxidase