Meeting Abstract
In insects the large number of sense organs can be subdivided into groups based on their morphology and corresponding function. The molecular and morphological development of sense organs has mainly been analysed in Drosophila melanogaster. Sense organ development requires proneural genes for the selection of sensory organ progenitors (SOPs), but also for their subtype identity. The proneural genes of the Achaete-Scute family, for example, are required for external mechanosensory organ development, while members of the Atonal family specify chordotonal organs and a subset of olfactory sense organs among others. We investigate the morphological and molecular development of sensory organs in Daphnia magna to address the question if evolutionary changes in the expression and function of proneural genes correlate with modifications in structure and function. Surprisingly, we found that in D. magna ASH and atonal are expressed in an overlapping pattern in several areas of the peripheral nervous system. Examples are the distal parts of the antennae, the mandible and the thoracic appendages, as well as the posterior margin to the proctodeum. Since it is not known which sense organs are generated in these areas, we are analyzing the structure and function of the larval sense organs and trace their origin back to embryonic stages. The partial co-expression of ASH and atonal in D. magna indicate that either the molecular mechanisms in sense organ determination have changed during crustacean evolution or that sense organs are formed that show characteristics distinct from insect sense organs. Therefore, we used stable germ line transformation to create D. melanogaster transformants, which carry the Daphnia atonal gene in order to perform over-expression and rescue experiments.
