The Effects of Male Seminal Fluid Proteins on Gut/Gonad Interactions in Drosophila

SIMPLE SUMMARY: The functions of organ systems must be coordinated for physiological homeostasis to occur. For example, after mating, coordination between insect digestive and reproductive systems is needed to ensure adequate nutrition for efficient egg/progeny production, and, conversely, to attune egg production levels to nutrient availability. Recent studies of Drosophila have revealed much about the post-mating changes in female reproductive tract function and in gut homeostasis, and the induction of these changes by male seminal proteins. Interesting regulatory connections between the organ systems and their responses have come to light in those studies. We have gathered these data into a single network schematic of the signaling events that operate within and between the reproductive and digestive systems downstream of seminal fluid proteins, summarizing current knowledge of the crosstalk between the systems and raising open questions for future study. ABSTRACT: Mating initiates broad physiological changes encompassing multiple organ systems in females. Elucidating the complex inter- and intra-organ signaling events that coordinate these physiological changes is an important goal in the field of reproductive biology. Further characterization of these complex molecular and physiological interactions is key to understanding how females meet the energetic demands of offspring production. Many recent studies of the fruit fly, Drosophila melanogaster, have described the mechanisms of post-mating changes within the female reproductive tract and digestive system. Additionally, other studies have described post-mating signaling crosstalk between these systems. Interestingly, male seminal fluid proteins have been linked to post-mating responses within the female reproductive tract and gut, and to signaling events between the two organ systems. However, information about the hormonal and neuronal signaling pathways underlying the post-mating signaling events within and between the reproductive tract and digestive systems that are triggered by seminal fluid proteins has yet to be combined into a single view. In this article, we summarize and integrate these studies into a single “network schematic” of the known signaling events within and between the reproductive and digestive systems downstream of male seminal fluid proteins. This synthesis also draws attention to the incomplete parts of these pathways, so that outstanding questions may be addressed in future studies.