Abstract
Octopamine is an important neuroactive substance that modulates several physiological functions and behaviors of invertebrate species. Its biosynthesis involves two steps, one of which is catalyzed by Tyramine beta-hydroxylase enzyme (TBH). The Tbetah gene has been previously cloned from Drosophila melanogaster, and null mutations have been generated resulting in octopamine-less flies that show profound female sterility. Here, I show that ovulation process is defective in the mutant females resulting in blockage of mature oocytes within the ovaries. The phenotype is conditionally rescued by expressing a Tbetah cDNA under the control of a hsp70 promoter in adult females. Fertility of the mutant females is also restored when TBH is expressed, via the GAL4-UAS system, in cells of the CNS abdominal ganglion that express TBH and produce octopamine. This neuronal population differs from the dopamine- and serotonin-expressing cells indicating distinct patterns of expression and function of the three substances in the region. Finally, I demonstrate that these TBH-expressing cells project to the periphery where they innervate the ovaries and the oviducts of the reproductive system. The above results point to a neuronal focus that can synthesize and release octopamine in specific sites of the female reproductive system where the amine is required to trigger ovulation.
