The role of <i>fruitless</i> in specifying courtship behaviors across divergent <i>Drosophila</i> species.

Abstract

Sex-specific behaviors are critical for reproduction and species survival. The sex-specifically spliced transcription factor <i>fruitless</i> (<i>fru</i>) helps establish male courtship behaviors in invertebrates. Forcing male-specific <i>fru</i> (<i>fruM</i>) splicing in <i>Drosophila melanogaster</i> females produces male-typical behaviors while disrupting female-specific behaviors. However, whether <i>fru</i>'s joint role in specifying male and inhibiting female behaviors is conserved across species is unknown. We used CRISPR-Cas9 to force FruM expression in female <i>Drosophila virilis</i>, a species in which males and females produce sex-specific songs<i>.</i> In contrast to <i>D. melanogaster</i>, in which one <i>fruM</i> allele is sufficient to generate male behaviors in females, two alleles are needed in <i>D. virilis</i> females. <i>D. virilis</i> females expressing FruM maintain the ability to sing female-typical song as well as lay eggs, whereas <i>D. melanogaster</i> FruM females cannot lay eggs. These results reveal potential differences in <i>fru</i> function between divergent species and underscore the importance of studying diverse behaviors and species for understanding the genetic basis of sex differences.