Insect Espionage: Molecular Mechanisms of Caterpillar Subversion of Host Plant Defenses

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Despite heavy agricultural pesticide use, global crop losses due to insect herbivory exceed 13%. In Canada, yield losses are expected worsen as global warming progresses as new migrant insect pest species are predicted to become established coupled with increases in pest infestations due to more generations because of longer summers and lower pest mortality due to milder winters. Therefore, under predicted future climatic conditions, insect pest pressure will increase and further challenge agricultural systems. Plants have endogenous physical and chemical means to protect themselves against caterpillar herbivory, however, insect herbivores also have strategies to counteract these plant defenses. Our research program focuses on understanding the mechanisms underlying these complex plant-insect interactions with the goal of defining strategies to maximize endogenous plant defenses while minimizing caterpillar subterfuge to lead to sustainable pest management practices under changing climatic conditions. A main theme of this research program is to understand how plants regulate defensive pathways induced in response to caterpillar herbivory and how caterpillar salivary effectors activate opposing plant hormone-regulated pathways to weaken the plant's ability to mount an effective defense response. Post-translational modification (PTM) is a dynamic and powerful cellular regulatory mechanism to alter protein activity (activity, localization, regulation, protein-protein interactions, stability). We have previously identified plant proteins that are modified in response to effectors secreted in the caterpillar's saliva. Based on this, we propose that, through their saliva, some noctuid caterpillar pests alter plant signaling pathways through the PTM of key regulatory proteins and dampen the induction of plant defense responses. This research will lead to sustainable agricultural practices and strengthen Canada's agricultural biotechnology industries by 1) furthering our understanding of the regulation of plant defenses against caterpillar herbivory 2) understanding insect strategies of suppressing the induction of plant defenses to develop strategies to manipulate insect performance in pest management. Funding for this project will support the training of graduate students (2.5 PhD, 1 MSc), undergraduates (2/yr) and a part-time research assistant in areas of high employment potential in Canada, such as molecular biotechnology and plant and insect biochemistry and physiology. Such background and training is vital for Canadian industries including agricultural biotechnology.