The sex difference in the reproductive response to starvation in <i>Drosophila melanogaster</i> is primarily located in the periphery rather than the nervous system

In many species, the reproductive behavior of females is more sensitive than that of males to energetic challenges, but the physical location of this sex difference is not completely understood. Progress has been facilitated by using <i>Drosophila melanogaster</i>, a genetically tractable species in which reproductive success is closely linked to energetics, and in which only females significantly decrease copulation rate after 48 h of food deprivation (FD). To examine the locus of the sex difference, we masculinized cells of either the nervous system (NS) or the fat body, an analog of the mammalian liver, using transcription inhibition of the sex determination cofactor, <i>transformer-2</i> (<i>tra2</i>). In genetic (XX) females with a masculinized NS, courtship behavior was masculinized so that they showed robust courtship toward other females, and yet, the response to FD was not masculinized (FD XX females with a masculinized NS and FD female controls both courted and copulated significantly less than their fed counterparts). Thus, a masculinized NS circuit that engages male-typical courtship behavior toward other females is not sufficient to create the male-typical low sensitivity to food deprivation. By contrast, in genetic XX females with a masculinized fat body, the reproductive response to FD was masculinized, perhaps increasing peripheral fuel availability to the brain. These results are consistent with the existence of an evolutionarily conserved mechanism whereby sex determining genes either masculinize or feminize the peripheral organs, such as the fat body, so that males and females use a different reproductive strategy in habitats where food availability fluctuates.<b>NEW & NOTEWORTHY</b> In <i>Drosophila melanogaster</i>, food-deprived (FD) females show significantly greater decreases in copulation rate and increases in time spent with food compared with males. Genetic XX females with a masculinized fat body, but not genetic females with a masculinized nervous system (NS), showed a masculinized response to FD, consistent with the idea that sex differences in the female reproductive response to FD lie primarily in the periphery and not the NS.