Amino acid change in an orchid desaturase enables mimicry of the pollinator’s sex pheromone

Mimicry illustrates the power of selection to produce phenotypic convergence in biology [ 1 ]. A striking example is the imitation of female insects by plants that are pollinated by sexual deception of males of the same insect species [ 2–4 ]. This involves mimicry of visual, tactile, and chemical signals of females [ 2–7 ], especially their sex pheromones [ 8–11 ]. The Mediterranean orchid Ophrys exaltata employs chemical mimicry of cuticular hydrocarbons, particularly the 7-alkenes, in an insect sex pheromone to attract and elicit mating behavior in its pollinators, males of the cellophane bee Colletes cunicularius [ 11–13 ]. A difference in alkene double-bond positions is responsible for reproductive isolation between O. exaltata and closely related species, such as O. sphegodes [ 13–16 ]. We show that these 7-alkenes are likely determined by the action of the stearoyl-acyl-carrier-protein desaturase (SAD) homolog SAD5. After gene duplication, changes in subcellular localization rela...