Reverse chemical ecology at the service of conservation biology.

Chemical ecology is the study of the chemical languages, cues, and mechanisms controlling interactions among living beings, including communication among individuals of the same species and between organisms and their environment. Organisms use chemicals to lure their mates, associate with symbionts, deter enemies, and fend off pathogens (1). Since the identification of the silkworm moth sex pheromone almost six decades ago (2), chemical ecologists have been deciphering hundreds of these “Rosetta Stones” (3) by using bioassay-guided protocols. This conventional chemical ecology approach is based on an invasive process of extracting secretions from chemical signal (semiochemical) senders (e.g., female moths), separating extracts into fractions, using receivers (e.g., male moths) to assist in the identification of active ingredients and, finally, by elucidating chemical structures and synthesis. The state-of-the-art techniques in chemical ecology have reduced analysis to even single individuals in many cases, but it is still too invasive for studying endangered or vulnerable species. In PNAS (4), a multidisciplinary group of scientists from China, Italy, and France apply tools of reverse chemical ecology (5) to study chemical communication in the giant panda, Ailuropoda melanoleuca, a vulnerable species endemic to China. The giant panda has an obligate bamboo diet and a carnivorous digestive system (6), which leads to a sedentary life with a limited reproduction rate, resulting in only a single offspring every other year. This mismatch of lifestyle and physiology coupled with fragmented habitats in its native environment in southwest China placed the giant panda on a list of endangered species until last year. Conservation campaigns would benefit from understanding at the molecular level how the giant pandas communicate among themselves and with the environment. Zhu et al. (4) use genomics, proteomics, functional analysis, and structural biology to get a better understanding of chemical communication and host–plant interactions in the giant panda. First, the authors analyze the panda genome to identify putative odorant-binding protein (OBP) genes. OBPs have been identified by two independent groups almost simultaneously in the sensillum lymph of moths (7) and bovine nasal mucous (8). Their role in olfaction is still a matter of considerable debate, but it has been well established that, at a minimum, they are carriers of odorants from the external environment (air) through the aqueous compartments surrounding odorant receptors. In insects, OBP expression is more restricted to the sensillum lymph surrounding receptors (9), but in vertebrates OBPs are also involved in transporting semiochemicals from the site of production to the external environment (10). In short, in vertebrates OBPs are involved in the delivery and uptake of semiochemicals. Zhu et al. (4) A