Mechanisms of force generation and auditory amplification in auditory neurons of Drosophila melanogaster. Somdatta Karak¹, Julia Jacobs², Maurice Kernan³, Daniel Eberl², Martin Goepfert¹. 1) Schwann Schleiden Forschungszentrum, Univ of Goettingen, Goettingen, Niedersachsen, Germany; 2) 269BB, Dept. of Biology, Univ of Iowa, Iowa, IA 52242, USA; 3) Dept. of Neurobiology and Behavior, SUNY, New York, USA.

   Hearing in both vertebrates and invertebrates employ an amplifier to enhance sensitivity of auditory neurons, enabling detection of low intensity sounds. Prestin in vertebrate hair cells changes conformation of the hair cells in a voltage dependent way and thus confers electromotility and amplification (Zheng et al, 2000). Though it is known that auditory neurons of Drosophila melanogaster are motile, the molecular mechanism of this process yet remains to be elucidated. Though prestin homologs are reported in fly auditory system experiments have failed to show its role as a molecular motor to facilitate amplification. The gating spring model predicts a positive interplay between ion channels and adaptation motors that leads to both auditory amplification as well as adaptation (Nadrowski et al, 2008). The dynein arms in the axoneme of the ciliated dendrites of auditory neurons hint at the role of axonemal dyneins in force generation and ciliary motility. Using laser Doppler vibrometry we analyzed roles of axonemal dynein mutants in auditory amplification. We show that axonemal dynein intermediate chain dmDNAI2 is required for auditory amplification and generation of sound-evoked action potentials. On the other hand we demonstrate that axonemal dynein heavy chain dmDNAH3 is dispensable for amplification but is required for generation of action potentials suggesting its probable role in electrical signal propagation along the length of the cilium. Epistatic analyses suggest that both the axonemal dyneins act downstream to TRPV channels present along the length of the cilia to facilitate amplification. Thus, our results hint towards at least two different roles of axonemal dyneins regulated by TRPV channels, as a direct force generator and a modulator of force generation in auditory neurons.