Mechanotransduction and auditory transduction in Drosophila

Abstract

Insects are utterly reliant on sensory mechanotransduction, the process of converting physical stimuli into neuronal receptor potentials. The senses of proprioception, touch, and hearing are involved in almost every aspect of an adult insect's complex behavioral repertoire and are mediated by a diverse array of specialized sensilla and sensory neurons. The physiology and morphology of several of these have been described in detail; genetic approaches in Drosophila, combining behavioral screens and sensory electrophysiology with forward and reverse genetic techniques, have now revealed specific proteins involved in their differentiation and operation. These include three different TRP superfamily ion channels that are required for transduction in tactile bristles, chordotonal stretch receptors, and polymodal nociceptors. Transduction also depends on the normal differentiation and mechanical integrity of the modified cilia that form the neuronal sensory endings, the accessory structures that transmit stimuli to them and, in bristles, a specialized receptor lymph and transepithelial potential. Flies hear near-field sounds with a vibration-sensitive, antennal chordotonal organ. Biomechanical analyses of wild-type antennae reveal non-linear, active mechanical properties that increase their sensitivity to weak stimuli. The effects of mechanosensory and ciliary mutations on antennal mechanics show that the sensory cilia are the active motor elements and indicate distinct roles for TRPN and TRPV channels in auditory transduction and amplification.

TRPA channels distinguish gravity sensing from hearing in Johnston's organ

“…Those results raise the possibility that in Drosophila gravity perception cap cells and their Pyx channels might actively respond to motion and participate in mechanosensory signaling. In addition, cap cells in Drosophila larval chordotonal organs contain numerous aligned microtubules (6,(32)(33)(34), and motility of those microtubules is thought to modulate tension in the chordotonal organ (4). Thus, another possibility is that Pyx channels trigger contraction or microtubule motility in Johnston's organ cap cells to influence gravity signals.…”

Agar-polydimethylsiloxane devices for quantitative investigation of oviposition behaviour of adult Drosophila melanogaster

“…1,[12][13][14] Oviposition is the process of egg-laying in D. melanogaster that is dependent on responses of the fly to environmental stimuli (such as chemicals, physical conditions of the substrate, temperature, light, population density, and humidity). [15][16][17][18][19] D. melanogaster possesses sensory neurons (such as taste 20,21 and touch 22,23 sensing systems) to detect various environmental cues prior to selecting preferred sites for oviposition and egg laying. [15][16][17][18][19] Therefore, oviposition is used as a metric quantity to provide a clear indication of flies' sensory system health and their overall fitness (the ability to survive and reproduce).…”

“…[15][16][17][18][19] D. melanogaster possesses sensory neurons (such as taste 20,21 and touch 22,23 sensing systems) to detect various environmental cues prior to selecting preferred sites for oviposition and egg laying. [15][16][17][18][19] Therefore, oviposition is used as a metric quantity to provide a clear indication of flies' sensory system health and their overall fitness (the ability to survive and reproduce). 24,25 It is used predominately in developmental, 26 chemical screening, 27 and toxicology 28,29 studies as a simple and effective readout indicator.…”

Separate TRP channels mediate amplification and transduction in drosophila

“…Impinging sound stimuli force the distal segment of the antenna to rotate on its long axis, and this rotation transmits force to the more proximal portion of the antenna, just as rotating a key transmits force to a lock. This force is transduced by auditory receptor neurons in Drosophila, termed Johnston's organ neurons (JONs), which are thought to be activated by stretch, opening mechanosensitive channels [5,6,9]. Sound-sensitive JONs are bidirectionally gated, such that they are activated by rotation of the antenna in either direction.…”