Thermosensory Transduction Mechanisms in Drosophila melanogaster

by Robert Kossen
Doctoral thesis
Date of Examination:2019-08-28
Date of issue:2019-10-18
Advisor:Prof. Dr. Martin Göpfert
Referee:Prof. Dr. Martin Göpfert
Referee:Prof. Dr. Ernst A. Wimmer
Referee:Prof. Dr. Manuela Schmidt
Referee:Prof. Dr. Tim Gollisch
Referee:PD Dr. Roland Dosch
Referee:Dr. Jan Clemens
Persistent Address: http://dx.doi.org/10.53846/goediss-7685

 

 

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Abstract

English

Ambient temperature has an profound effect in the physiology of all animals and accurate evaluation of both external and internal temperatures is therefore an essential factor for fitness and survival. To this end, animals possess specialized cells and organs, which have evolved to obtain accurate information about this crucial factor. Drosophila melanogaster relies on different thermosenstive neurons to gauge both its internal as well as the external temperature. One thermosensitive organ is located in the arista, a feather like structure protruding from the third segment of the fly’s antenna. It has been found that the arista houses six neurons, three of which exhibit excitatory responses to heat (and were therefore called hot cells) and three which are responding to cold (named cold cells). In this study, I characterized the responses properties of the thermosensory organ in the arista and I analyzed the role that the TRP ion channel NOMPC, classically associated with mechanosensation, plays in this particular structure. Using Ca2+ imaging, I found that the amplitude of temperature evoked Ca2+ responses appears to be determined by the relative change in temperature, rather than the absolute value. I furthermore found evidence that the TRP channel NOMPC can be found in the hot cell population of arista neurons. Data obtained in this study shows that a knockdown of nompC leads to a reduction in the temperature response amplitude of hot cells. Homozygous nompC null mutants exhibit a stronger reduction in amplitude than heterozygous mutants, hinting at a possible gene dosage effect. The response modulation via NOMPC also affects behaviour, as locomotion experiments in a temperature gradient showed that nompC knockdown mutants show later hot avoidance and have a higher preferred temperature. The effect in both physiological and behavioural experiments could be rescued. Taken together, the findings of this study show that the thermosensitive neurons in the arista of Drosophila function as relative temperature sensors and that NOMPC serves an important modulatory role for the temperature evoked responses of these neurons.
Keywords: Drosophila; Temperature; Thermosensation; Calcium Imaging; Behaviour; Arista; NompC
 
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