D3392: Does insect's salivary enzyme activate the defense response in wiild tomato species?

Plant domestication has altered the defenses in plants because breeders have selectively chosen some desirable traits (taste, size, color) from wild species to improve the cultivated ones. Some cultivated plants have been reported to perform worse than their wild ancestors while others had higher defenses when attacked by pathogenic insects through their salivary enzyme known as glucose oxidase (GOX). Despite the studies on how GOX acts to modulate plants defenses especially in cultivated plants, little information is known on how wild relatives respond to GOX. This study aims to evaluate the defense response of wild tomato species to GOX of Helicoverpa zea.

In this study, some accessions of Solanum pennellii were examined against herbivory using wild type (with GOX) and mutant (without GOX) generalist caterpillars (Helicoverpa zea; tomato fruitworm).Three treatments [Control (undamaged), wild type and mutant caterpillar feeding) were used to test the effect of GOX on the induction of defensive proteins; polyphenol oxidase and trypsin inhibitor (anti-nutritive enzymes), and peroxidase (anti-oxidative enzymes).

The results showed that, GOX did not induce anti-nutritive enzymes in all the accessions across all the treatments. However, the result from peroxidase activity showed a level of inducibility in all the accessions in wild type and mutant caterpillar feeding treatments compared to the undamaged plants.

In conclusion, our findings revealed that GOX secreted by H. zea does not induce anti-nutritive enzymes in all the accessions of S. pennellii but activated anti-oxidative enzyme indicating that other stressors might be involved in the process.