Mechanisms and Ecological Relevance of Direct Plant Responses to the Third Trophic Level

ongoing

Interactions between plants, herbivores and herbivore natural enemies, so-called tritrophic interactions, are important determinants of ecological processes and crop yields. Plants play an important role in tritrophic interactions through their capacity to recognize and respond to herbivores by activating defences. Interestingly, recent work shows that plants also respond directly to natural enemies of herbivores. However, the mechanisms and specificity of these responses are not well understood, and how they influence tritrophic interactions is unknown. PRENEMA aims at characterizing plant responses to the third trophic level as an hitherto overlooked mechanism governing tritrophic interactions. To this end, PRENEMA combines an interdisciplinary approach with a new phenotyping method and a tractable, ecologically and agriculturally relevant, tritrophic model system consisting of maize and its wild ancestor teosinte, the root herbivore Diabrotica balteata and the entomopathogenic nematode Heterorhabditis bacteriophora. In a first step, PRENEMA will develop a novel root exometabolome sampling system to simultaneously extract and profile root water-soluble and volatile exudate metabolites. Second, PRENEMA will use this system to characterize changes in maize primary and secondary metabolites upon exposure to entomopathogenic nematodes, and assess the specificity of the responses across different maize and teosinte genotypes and nematode species. Third, a subset of the identified response markers will be used to uncover nematode-associated molecular patterns that are responsible for triggering plant responses. Fourth, the ecological consequences of the plant responses for plants, herbivores and entomopathogenic nematodes will be measured in the greenhouse and the field. The knowledge and technology generated by PRENEMA will help to integrate a new infochemical pathway into tritrophic interactions and will advance the state of the art in belowground chemical ecology.