Insects are not passive victims to plant defences. They have evolved to overcome the dietary challenges such as toxic secondary metabolites produced by the host plant. Several insect species have evolved mechanisms to adapt to plant toxins and also use them for their own survival and mating. Such specialist insect herbivores are extremely interesting to study to understand their adaptation mechanisms. Specialist insects adapt to plant chemicals either by rapid excretion, detoxification or sequestration We study the detoxification mechanism of insects to understand the co-evolutionary arms race between plants and insects. In general, detoxification occurs in two phases in insects. Phase I enzymes such as Cytochrome P450s help to functionalize of the xenobiotics and Phase II enzymes help in converting lipophilic compounds into hydrophilic compounds that can be easily excreted or sequestered. Phase II enzymes include glutathione S-transferases (GSTs) and UDP-glucosyltransferases. Although insects possess several of these detox enzymes, only a small number of these enzymes are involved in the actual metabolism of xenobiotics. A major challenge in understanding insect adaptation is to identify host plant metabolites that exert direct physiological and behavioral effects on the insect herbivore. Given the complexity of plant biochemistry, the first step would be dissect individual toxins and evaluate their effect on the herbivore. Currently we are focusing on fern toxin, Ptaquiloside and ricinine tolerance in insects. We use Spodoptera litura and Helicoverpa armigera as lab models to understand these mechanisms. Further, field caught specialist insects that are highly adapted to these toxins are also under study.
Gut microorganisms in the insect herbivore make significant contribution in adaptation to host plant allelochemicals. Participation of gut microbes in transformation of plant chemicals is an important aspect to be considered in the plant-insect relationships. However, given the complexity of the gut microbes, there is lack of detailed investigations in several systems. We also attempt to study the role of gut microbiota in insect adaptation.
Gut microorganisms in the insect herbivore make significant contribution in adaptation to host plant allelochemicals. Participation of gut microbes in transformation of plant chemicals is an important aspect to be considered in the plant-insect relationships. However, given the complexity of the gut microbes, there is lack of detailed investigations in several systems. We also attempt to study the role of gut microbiota in insect adaptation.