Ovulation requires female reproductive tract secretions controlled by NR5a-family nuclear hormone receptors. Jianjun Sun, Allan Spradling. HHMI Laboratory, Department of Embyology, Carnegie Institution for Science, Baltimore, MD.

   Ovulation is an important, general phenomenon yet its molecular control remains poorly understood. We report that Drosophila can be used to study the molecular genetic mechanisms regulating ovulation, and that several cellular and molecular mechanisms previously thought to be unique to mammals appear to be conserved in the fly. In particular, we found that the NR5a-family nuclear hormone receptor Hr39 is required for ovulation, like its homolog LRH-1 in mice. In Drosophila, Hr39 controls the development of the glands of the female reproductive system, known as spermathecae and parovaria. Hence Hr39 mutants lack reproductive tract secretions. The development of these glands was characterized for the first time and shown to involve asymmetric divisions, the Notch signaling, and the zinc-finger transcription factor Hindsight. Using this knowledge we manipulated the number of secretory cells and hence the amount of secretion in the reproductive tract. We showed that secretions play critically important functions in ovulation, sperm storage, and other aspects of reproduction. We also identified specific genes encoding secreted products in the spermathecae, including many that are conserved in mammals, and identified their likely functions.