Authors: Iris Cepeda, Tabitha Weir, Jonathan Cook, Honey Ordonez
Mentors: Olga Kopp
Insitution: Utah Valley University
Solanum lycopersicum (tomatoes), are beloved herbaceous crops well known for their red bearing fruits. They are best grown in well-draining soils with access to full sun and are endemic to South America but grow all across the world where the conditions allow. Tomato fruits provide a quality source of phytochemicals and antioxidants such as lycopene, vitamin C, beta-carotene, and phenolic compounds which can substantially improve one’s healthy diet. S. lycopersicum are members of the nightshade family, which are known for their production of often toxic glycoalkaloids. The presence of these compounds usually deters herbivores by increasing their concentration as a defense response. There are, however, herbivores like Manduca sexta (tobacco hornworms) that feed on members of the nightshade family by dealkylating these glycoalkaloids.
It is hypothesized that plants have the ability to modulate their defensive response based on queues from the environment and from their herbivore pests. Our research objective is to determine whether a S. lycopersicum plant undergoing defoliation from M. sexta will have the same molecular response as a plant undergoing simulated herbivory.
Four treatment groups will be used with each treatment group having 8 replicates. Before treatment begins, the groups will be isolated by a non-permeable surface so air-borne defense signals from one group do not elicit a response in another. In the herbivory treatment group, M. sexta will be allowed to feed for a 24-hour period to account for diurnal and nocturnal herbivory, as well as high plant enzymatic response. Damage treatment 1 will simulate herbivory using a hole-punch, avoiding the midvein. Damage treatment 2 will simulate herbivory using a single transverse cut across the leaf blade and midvein. The undamaged control will have no herbaceous or mechanical damage done. After the treatment period, half of the leaf matter from all groups will be collected and frozen in liquid nitrogen to preserve all metabolic processes and GCMS will be used to analysis metabolite differences. The other half of the leaf matter will be analyzed using UV-spectrophotometer analysis with bromocresol green to compare the glycoalkaloid expression between the treatments.
It’s expected that there will be a reduced expression of the defense glycoalkaloids in the herbivory group of S. lycopersium when compared to the two defoliation groups. While the three treatments could respond similarly to their treatments by primary metabolite expression, the type of defoliation could have a greater effect on this than the herbivory group.