Salivary glucose oxidase (GOX) is one of the most abundant salivary proteins in generalist caterpillar Helicoverpa zea. GOX has been hypothesized to benefit H. zea by modulating direct defense responses of plants. Although the function of this protein has been studied, its role remains unclear. The study aims to test the hypothesis that GOX induces similar defensive responses among Solanaceous plants, and has similar consequences for larval performance of H. zea. Using six different plants in Solanaceae, including tomato (Solanum lycopersicum cv. Better Boy and S. lycopersicum var. cerasiforme), bell pepper (Capsicum annuum cv. Revolution), habanero pepper (Capsicum chinense), tomatillo (Physalis philadelphica cv. Tamayo), and tobacco (N. benthamiana), we tested the impact of GOX on induction of two common defense proteins, trypsin protease inhibitors (TPI) and polyphenol oxidases (PPO), and on relative growth rate of H. zea larvae. We found that GOX specifically induced TPI activity in tomato and habanero pepper, and the level of defense protein depended on leaf location. In addition, prior application of GOX did not increase the performance of H. zea in any plant tested. Changes in performance in tomato and habanero pepper matched the induction of TPI. In summary, our findings indicate that GOX induces similar defense responses in some Solanacean plants, but largely depends on species/genotype of plant, and that the presence of GOX did not benefit larval H. zea by modulating direct defense responses of plants. Other mechanisms must be involved in driving the evolution of this salivary protein.
All Science Journal Classification (ASJC) codes
- Ecology, Evolution, Behavior and Systematics
- Agronomy and Crop Science
- Insect Science