R. J. Driver, M. A. Marie, V. J. Ko, P. Meesa, W. Sun, R. J. Li, M. S. Brewer, H.-Y. Lu, K. F. P. Bennett, M. Sollitto, G. Formenti, I. Ojiro, N. E. Mantha, H. Matsunami, C. N. Balakrishnan
Abstract: Odorant receptors (ORs) form among the largest gene families in vertebrates; most mammals have hundreds of intact OR genes. Although birds display diverse behavior and ecology, they were long thought to rely minimally on olfaction. We reexamine this idea by using genomic data to uncover diverse and variable OR repertoires in birds, including the nocturnal kiwi (Apteryx mantelli), which possesses the largest number of ORs known (3,750). We reveal that widespread gene conversion is shaping the evolution of bird ORs, reflecting a novel mechanism for generating functional diversity. We show that ORs are expressed in avian olfactory sensory neurons and show responses to defined, ecologically relevant odorants. Our results demonstrate the importance and functional mechanisms underlying olfaction in birds.