Abstract
Food and sex often go hand in hand because of the nutritional cost of reproduction. For Drosophila melanogaster females, this relationship is especially intimate because their offspring develop on food. Since yeast and sugars are important nutritional pillars for Drosophila, availability of these foods should inform female reproductive behaviours. Yet mechanisms coupling food and sex are poorly understood. Here we show that yeast increases female sexual receptivity through interaction between its protein content and its odorous fermentation product acetic acid, sensed by the Ionotropic odorant receptor neuron Ir75a. A similar interaction between nutritional and hedonic value applies to sugars where taste and caloric value only increase sexual receptivity when combined. Integration of nutritional and sensory values would ensure that there are sufficient internal nutrients for egg production as well as sufficient environmental nutrients for offspring survival. These findings provide mechanisms through which females may maximize reproductive output in changing environments.