D3061: Phytohormones and their effects on aster leafhopper behavioral responses

Stimuli such as infection with one or multiple pathogens and insect herbivory trigger morphological, physiological, and molecular responses in plants. One of these plant responses involves the production of chemical compounds such as secondary metabolites, which can modulate insect behavior. Signaling pathways involved in the production of these chemicals are regulated by various plant hormones, with jasmonic acid (JA), ethylene (ET), and salicylic acid (SA) being the most important ones. Phytoplasmas are a group of obligate parasites that require an insect vector for transmission to another plant host and are associated with several plant diseases. In the Canadian Prairies, Aster Yellows (AY) disease is caused by the infection with phytoplasma subgroup 16SrI, which is transmitted by migratory populations of aster leafhoppers (Macrosteles quadrilineatus Forbes). Previous studies suggest that AY infection is associated with the downregulation of different components involved in the JA signaling pathway. It remains unclear, however, if other major plant hormones such as ET and SA also contribute to plant responses to phytoplasma infection, which can potentially affect this vector’s behavioral responses. To provide a better understanding of the role of plant signaling pathways in aster leafhoppers’ feeding, oviposition, development, and host choice selection behavior, we conducted no-choice and two-choice bioassays using a selection of Arabidopsis thaliana lines that vary in their defense pathways. We additionally evaluated whether these factors are affected by phytoplasma infection by conducting bioassays with AY-infected Aster leafhoppers. Gene expression of marker genes involved in plant signaling pathways was also measured.