Potential role of ascorbate oxidase as a plant defense protein against insect herbivory

Ascorbic acid is essential for both nutritive and antioxidant functions in phytophagous insects; however, maintaining sufficient quantities of reduced ascorbate may be problematical for them. In this investigation, we show that the plant enzyme ascorbate oxidase retains activity in the digestive sys...

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Bibliographic Details
Published in:Journal of chemical ecology 1993-07, Vol.19 (7), p.1553-1568
Main Authors: FELTON, G. W, SUMMERS, C. B
Format: Article
Language:English
Subjects:
acide ascorbique
acido ascorbico
Agronomy. Soil science and plant productions
ascorbic acid
Biological and medical sciences
control de insectos
estres
Fundamental and applied biological sciences. Psychology
Genetics and breeding of economic plants
glycine max
gossypium
Helicoverpa zea
insect control
Invertebrates
Lepidoptera
lutte antiinsecte
lycopersicon esculentum
Noctuidae
oxidoreductases
oxidorreductasas
oxydoreductase
Pest animals
Pest resistance
resistance aux organismes nuisibles
resistencia a las plagas
stress
Varietal selection. Specialized plant breeding, plant breeding aims
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Summary:Ascorbic acid is essential for both nutritive and antioxidant functions in phytophagous insects; however, maintaining sufficient quantities of reduced ascorbate may be problematical for them. In this investigation, we show that the plant enzyme ascorbate oxidase retains activity in the digestive system of the herbivore Helicoverpa zea. High levels of the enzyme are present in several host plants of H. zea, including cotton, tomato, soybean, crimson clover, and vetch. The enzyme oxidizes L-ascorbic acid to dehydro-L-ascorbic acid, a potentially toxic product. The oxidation of ascorbic acid also produces active oxygen species such as the highly reactive hydroxyl radical. The nutritional quality of protein for larval H. zea was significantly reduced by treatment with ascorbate and ascorbate oxidase. Oxidative damage to the protein was indicated by decreased lysine content, increased carbonyl formation, and the occurrence of protein fragmentation and polymerization. Furthermore, the oxidative loss of ascorbate in the herbivore's digestive system prevents ascorbate from functioning as an important antioxidant against a plethora of dietary prooxidants.
ISSN:0098-0331
1573-1561
DOI:10.1007/bf00984896