Howlett et al. BMC Genomics 2012, 13:211 http://www.biomedcentral.com/1471-2164/13/211 R E S E A R C H A R T I C L E Open Access Identification of chemosensory receptor genes in Manduca sexta and knockdown by RNA interference Natalie Howlett†, Katherine L Dauber†, Aditi Shukla, Brian Morton, John I Glendinning, Elyssa Brent, Caroline Gleason, Fahmida Islam, Denisse Izquierdo, Sweta Sanghavi, Anika Afroz, Aanam Aslam, Marissa Barbaro, Rebekah Blutstein, Margarita Borovka, Brianna Desire, Ayala Elikhis, Qing Fan, Katherine Hoffman, Amy Huang, Dominique Keefe, Sarah Lopatin, Samara Miller, Priyata Patel, Danielle Rizzini, Alyssa Robinson, Karimah Rokins, Aneta Turlik and Jennifer H Mansfield* Abstract Background: Insects detect environmental chemicals via a large and rapidly evolving family of chemosensory receptor proteins. Although our understanding of the molecular genetic basis for Drosophila chemoreception has increased enormously in the last decade, similar understanding in other insects remains limited. The tobacco hornworm, Manduca sexta, has long been an important model for insect chemosensation, particularly from ecological, behavioral, and physiological standpoints. It is also a major agricultural pest on solanaceous crops. However, little sequence information and lack of genetic tools has prevented molecular genetic analysis in this species. The ability to connect molecular genetic mechanisms, including potential lineage-specific changes in chemosensory genes, to ecologically relevant behaviors and specializations in M. sexta would be greatly beneficial. Results: Here, we sequenced transcriptomes from adult and larval chemosensory tissues and identified chemosensory genes based on sequence homology. We also used dsRNA feeding as a method to induce RNA interference in larval chemosensory tissues. Conclusions: We report identification of new chemosensory receptor genes including 17 novel odorant receptors and one novel gustatory receptor. Further, we demonstrate that systemic RNA interference can be used in larval olfactory neurons to reduce expression of chemosensory receptor transcripts. Together, our results further the development of M. sexta as a model for functional analysis of insect chemosensation. Background Animals rely on their olfactory and gustatory systems to detect chemicals in their environments. Chemosensation mediates essential behaviors such as locating food and shelter, avoiding predators, locating mates, and selecting appropriate sites for nesting or laying eggs. The chemo- sensory organs and the gene families that encode che- mosensory proteins are different in vertebrates and insects, but the underlying logic is in some respects quite similar [1,2]. * Correspondence: jmansfield@barnard.edu †Equal contributors Department of Biological Sciences Barnard College, Columbia University, 3009 Broadway, New York, NY 10027, USA The molecular basis of insect chemosensation is best understood in Drosophila. Responses to gustatory and olfactory cues are mediated by the olfactory (OR) and gustatory (GR) receptors, which together comprise an insect chemoreceptor super-family. Receptor protein complexes (which for ORs include the conserved co- receptor protein Orco) function as ionotropic membrane channels, whose precise mechanism of action is still under investigation [reviewed in [2], and see also [3–5]]. OR and GR receptors are expressed in Olfactory Recep- tor Neurons (ORNs) and Gustatory Receptor Neurons (GRNs) respectively. Most ORNs express a single con- ventional OR, and the range of compounds to which they respond depends on the tuning of that receptor. © 2012 Howlett et al.; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.