Silencing <i>Doublesex</i> expression triggers three-level pheromonal feminization in <i>Nasonia vitripennis</i> males

Abstract

Doublesex (Dsx) has a conserved function in controlling sexual morphological differences in insects, but our knowledge of its role in regulating sexual behaviour is primarily limited to <i>Drosophila</i>. Here, we show with the parasitoid wasp <i>Nasonia vitripennis</i> that males whose <i>Dsx</i> gene had been silenced (<i>NvDsx</i>-i) underwent a three-level pheromonal feminization: (i) <i>NvDsx</i>-i males were no longer able to attract females from a distance, owing to drastically reduced titres of the long-range sex pheromone; (ii) <i>NvDsx</i>-i males were courted by wild-type males as though they were females, which correlated with a lower abundance of alkenes in their cuticular hydrocarbon (CHC) profiles. Supplementation with realistic amounts of synthetic (<i>Z</i>)-9-hentriacontene (<i>Z</i>9C31), the most significantly reduced alkene in <i>NvDsx</i>-i males, to <i>NvDsx</i>-i males interrupted courtship by wild-type conspecific males. Supplementation of female CHC profiles with <i>Z</i>9C31 reduced courtship and mating attempts by wild-type males. These results prove that <i>Z</i>9C31 is crucial for sex discrimination in <i>N. vitripennis</i>; and (iii) <i>Nvdsx</i>-i males were hampered in eliciting female receptivity and thus experienced severely reduced mating success, suggesting that they are unable to produce the to-date unidentified oral aphrodisiac pheromone reported in <i>N. vitripennis</i> males. We conclude that Dsx is a multi-level key regulator of pheromone-mediated sexual communication in <i>N. vitripennis</i>.