Potential antagonistic cross-talk between defensive signaling pathways in tomato plants in response to a viral pathogen and an arthropod herbivore, and the effect on the third trophic level.

D.C. Margolies, P. Nachappa, J.R. Nechols, D. Rotenberg, A.E. Whitfield and L.R. Campbell

Plants are subject to attack by both pathogens and herbivores, and respond to attacks by up-regulating genes that affect several defensive pathways.   However, these pathways may be antagonistic to each other, which raises the question as to how plants coordinate defense responses to multiple and varied attackers.  It has been hypothesized that signal ‘crosstalk’ may prioritize the activation of a particular defense pathway over another, leading to the optimal defense against multiple attackers.   In tomato plants exposed individually and simultaneoulsy to a pathogen, tomato spotted wilt virus, and a herbivore, twospotted spider mite, we are: 1) assessing changes in general and specific plant gene expression in response to TSWV and TSM, both individually and together, using tomato microarrays followed by RT-PCR; and 2) determining the effect of plant response to a pathogen and herbivore, both individually and together, on the third trophic level both by behavioral bioassays and analysis of  compounds to which predators respond.