Tomato-mediated interactions between root herbivores and aphids: insights into plant defence signalling

Reactions of plants to insect pests include the activation of a local and systemic defence response. This response is based on transcriptional changes that are mainly controlled and coordinated by phytohormones. The above- and belowground part of plants can be challenged by different insects and therefore, the defence response to one attacker can influence other insects. The study of plant-mediated interaction between pests that are physically or temporally separated yielded a variety of outcomes, with positive, negative, and neutral effects described in the literature. In this study, we examined possible plant-mediated interactions between above- and belowground insect pests with different feeding guilds in tomato, Solanum lycopersicum L. (Solanaceae). Root feeding by Agriotes lineatus (L.) (Coleoptera: Elateridae) larvae caused a decrease in the development rate, fertility, and weight in Myzus persicae (Sulzer) (Hemiptera: Aphididae). To gain insights into the plant systemic signalling mechanisms, we also performed a time-course expression analysis of defence-related phytohormone marker genes. The result indicated a dynamic systemic response in leaves following root herbivory, which comprises the activation of genes dependent on different molecular pathways involved in plant stress response. Our work demonstrated that root herbivory increased aphid resistance in tomato and that a combination of signals enables the communication between below- and aboveground pests with different feeding guilds.