Chemosensory receptors in the tobacco hawkmoth Manduca sexta

Chemosensation, the sense of smell and taste, allows animals to assess the chemical properties of their environment. They use it to identify food sources, avoid harmful substances, find mating partners, escape from predators and to find places suitable for their offspring. We employed the tobacco hawkmoth Manduca sexta (Lepidoptera: Sphingidae) to study the molecular basis of chemosensation in the context of the insect’s environment. Therefore, we generated RNAseq data sets of several chemosenory tissues in several physiological states of M. sexta. We used this data to correct the gene models generated by an automated annotation pipeline as part of the M. sexta genome project to build a reference set of chemosensory receptor genes. This gene set will facilitate future Lepidoptera genome projects. We used the corrected and several new gene models to find sex specifically expressed genes and to characterize the chemosensory repertoire of larvae. Thus, I could formulate hypotheses about their role in the life of female and male moths as well as larvae. We report expression of chemosensory receptors in the ovipositor. Furthermore, we identified putative olfactory sensilla on the ovipositor and using electrophysiological recording we identified ligands which could be important for oviposition site selection. In a third study, we challenged M. sexta larvae by rearing them on host and non- host plants. We checked the expression of detoxification, immune system related and chemosensory genes to assess the ability of M. sexta larvae to adapt to their environment. This thesis provides insights into the molecular basis of chemosensation in different ecological contexts, following the life cycle of a lepidopteran species from mating and oviposition throughout the larval stage. The principles studied here in M. sexta can be applied and generalized to other insects and will facilitate further research in chemical