Differences in Nicotiana tabacum phytohormones signaling in response to oral secretion by Helicoverpa zea and Manduca sexta

Attacks from biotic agents such as herbivores stimulate the “immune-like” system of plants by the production of protease inhibitors and related defensive compounds which are regulated through the action of the phytohormones such as jasmonate and salicylate. In this experiment tobacco plants (Nicotiana tabacum) were grown from seeds for 8 weeks in an environmentally controlled growth chamber. The plants were then divided into three treatments of 10 plants with Helicoverpa zea caterpillar herbivory, Manduca sexta caterpillar herbivory, and no herbivory as the control treatment. The plants were monitored during feeding and after 24 hours, tobacco leaves from each treatment were harvested and flash frozen in liquid nitrogen. Total RNA was purified for both qPCR and microarray analysis which resulted in quite a number of significantly altered genes between the various treatments. A follow up experiment was performed to determine the role of jasmonate and salicylate. These experiments suggested that H. zea stimulates more SA related genes that M. sexta. However, the vast majority tobacco defense genes were conserved between the two herbivores.