The management of insect pests, from phytophagous and parasites to disease vectors requires a thorough knowledge of the mechanisms by which insects deal with chemical and biological challenges. These challenges to insect fitness can be viewed as a seamless range of aggressions, rather than categories of "pathogens" or "xenobiotics". The overall goal of our team is to exploit genomic resources to study the functional basis of insect defense mechanisms and their evolution.
1 – Insect defenses as determinant of plant exploitation: characterization and evolution
Defense processes are essential fitness-related traits determining survival and evolving under a combination of antagonistic selection pressures. In the case of grazing insects or phloem-feeders, they also directly determine their ability to exploit the plant through i) suppression or modulation of early local and later systemic events of plant defense response and ii) detoxification of plant toxic compounds (whether constitutively produced or resulting from the plant response to insect attack). We explore the question of the importance of insect defense processes as determinant of plant exploitation using several complementary projects using aphids and noctuid pests.
2 – Insect defenses as determinant of survival to xenobiotics
Herbivorous insects have developed detoxification mechanisms to inactivate the plant toxins that they ingest, often depending on expression of cytochromes P450. The nuclear receptors that control P450s are well understood in vertebrates, but remain poorly understood in invertebrates. The overall objective of this project is to investigate detoxification mechanisms in the polyphagous lepidopteran pest, Spodoptera frugiperda and to elucidate the signaling pathways involved in the mounting of a xenobiotic-adapted response. Our previous studies showed that the pattern of differentially transcribed genes were specific to each chemical tested suggesting multiple, partially overlapping pathways. Transcriptomic studies are used to further assess the specificity of the responses and to gain further information of the possible signaling pathways involved.
3 - Evolution of multigenic families involved in insect defenses
In support of the objectives described above, our team will continue to exploit genomic and transcriptomic resources to document the evolution of multigenic families such as cytokines, detoxification enzymes, receptors and transporters as a service to the community (annotation) and as a basis for the correct design and interpretation of experiments involving insect defenses.