Evolution of Olfactory Receptors Tuned to Mustard Oils in Herbivorous Drosophilidae |
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| Authors: | Teruyuki Matsunaga Carolina E Reisenman Benjamin Goldman-Huertas Philipp Brand Kevin Miao Hiromu C Suzuki Kirsten I Verster Santiago R Ramírez Noah K Whiteman |
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| Institution: | 1. Department of Integrative Biology, University of California Berkeley, Berkeley, CA, USA;2. Department of Molecular and Cell Biology, University of California Berkeley, Berkeley, CA, USA;3. Department of Molecular and Cellular Biology, University of Arizona, Tucson, AZ, USA;4. Department of Evolution and Ecology, University of California Davis, Davis, CA, USA |
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| Abstract: | The diversity of herbivorous insects is attributed to their propensity to specialize on toxic plants. In an evolutionary twist, toxins betray the identity of their bearers when herbivores coopt them as cues for host-plant finding, but the evolutionary mechanisms underlying this phenomenon are poorly understood. We focused on Scaptomyza flava, an herbivorous drosophilid specialized on isothiocyanate (ITC)-producing (Brassicales) plants, and identified Or67b paralogs that were triplicated as mustard-specific herbivory evolved. Using in vivo heterologous systems for the expression of olfactory receptors, we found that S. flava Or67bs, but not the homologs from microbe-feeding relatives, responded selectively to ITCs, each paralog detecting different ITC subsets. Consistent with this, S. flava was attracted to ITCs, as was Drosophila melanogaster expressing S. flava Or67b3 in the homologous Or67b olfactory circuit. ITCs were likely coopted as olfactory attractants through gene duplication and functional specialization (neofunctionalization and subfunctionalization) in S. flava, a recently derived herbivore. |
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| Keywords: | Drosophila melanogaster Scaptomyza flava herbivory evolution olfaction isothiocyanate chemoreceptor SSR olfactory receptor wasabi Brassicales Or67b gene duplication neofunctionalization subfunctionalization specialization olfactory specialization |
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