Courtship song in Drosophila is produced by the male's wing vibration and consists of pulses of tone produced at intervals of approximately 34 shortens the circadian period, perl, which lengthens it, and pero, which abolishes it-strikingly affects the 60-sec song rhythm in a parallel fashion. Therefore, both circadian rhythms and a very short, noncircadian oscillation appear to be influenced by the same gene.Courtship in Drosophila melanogaster consists of a series of highly stereotyped behavioral patterns, the most conspicuous of which is the male's wing display (1, 2). The male extends and vibrates his wing, producing a patterned acoustic signal or "song" (3). The song is illustrated in Fig. 1 and has several acoustic components, including a train of pulses with an interpulse interval (ipi) of approximately 34 msec together with a sinusoidal hum, which has a frequency of 160 Hz (4). The ipi is species specific; males of D. simulans, a closely related species, sing with an ipi of approximately 48 msec (5). Von Schilcher (6) has reported that D. melanogaster females mate faster with wingless, deafened conspecific males when they are exposed to an artificial song with an ipi of 34 msec compared to one having an ipi of 48 msec. Therefore, the ipi of the courtship song may play an important role as a recognition factor in preserving the sexual isolation between the two species.This paper describes some experiments that demonstrate that the variation in the ipi values produced by males of both D. melanogaster and D. simulans is greater than previously believed. However, we will show that this variation conforms to a highly structured temporal pattern which is dramatically affected in D. melanogaster by three circadian rhythm mutations isolated by behavioral criteria unrelated to courtship (7). 5-day-old male with a 3-day-old virgin attached-X female inside a transparent mating cell 2 X 1 X 0.3 cm high. The floor of the chamber was composed of Nytex (stiff nylon mesh), and the unit was placed 2 mm above the ribbon of a Reslo (Sheffield, England) ribbon microphone, which was then encased within a screened aluminum box (12 X 8 X 8 inches) which served as an anechoic chamber. A porthole was cut in the box to enable the experimenter to observe the flies. The song of the male was amplified and recorded on a Tandberg loX reel-to-reel tape recorder. A visual record of the song was obtained by tracing the recording, together with a time reference, on light-sensitive paper (Dupont, Type 5B) with a multichannel oscillograph (Consolidated Electrodynamics, Newark, NJ, type 5-124). The paper was exposed, and ipi were measured peak to peak with a ruler.The courtship was divided into 10-sec fractions, and the mean and SEM of all ipi falling within each successive time period was computed. The minimum number of ipi used to obtain a mean was 10, and most means were based on between 25 and 70 individual ipi. These means were then used to compute a nonlinear regression of ipi against the successive time periods for each court...
The developmental time of period mutants in Drosophila melanogaster was monitored under different environmental conditions. We observed that the pe? mutants, which have short 19 h circadian cycles, develop faster from eggs to adult than the wild-type: perL mutants, which have long 28 h circadian rhythms, complete development more slowly than the wild-type. These results suggest that endogenous timers may be involved in regulating the development time of D. melanogaster.
A number of insects produce acoustic signals during courtship. Genes involved in the control of the courtship song are particularly interesting from an evolutionary viewpoint because interspecific variation in this signal is potentially important as a reproductive isolation mechanism and, as a consequence, in the speciation process. The cacophony gene was identified by a mutation affecting the "lovesong" in Drosophila melanogaster. Phlebotomine sandflies (Diptera: Psychodidae) also produce acoustic stimuli during courtship and therefore cacophony can be used as an interesting molecular marker in evolutionary studies in these important disease vectors. In this paper we have studied the molecular evolution of the IVS6 region of cacophony in sandflies. We compared the level of divergence in the exon sequences encoding this conserved domain in Drosophila and Phlebotomines. We also analysed the high level of variation in an intron that is present in sandflies but that was lost in Drosophila during evolution. The available cacophony sequences were also used for a phylogenetic analysis of some species of the Neotropical genus Lutzomyia.
Huntington's disease (HD) is a fatal neurodegenerative disorder caused by expansion of a polyglutamine tract in the huntingtin protein (htt) that mediates formation of intracellular protein aggregates. In the brains of HD patients and HD transgenic mice, accumulation of protein aggregates has been causally linked to lesions in axo-dendritic and synaptic compartments. Here we show that dendritic spines -sites of synaptogenesis -are lost in the proximity of htt aggregates because of functional defects in local endosomal recycling mediated by the Rab11 protein. Impaired exit from recycling endosomes (RE) and association of endocytosed protein with intracellular structures containing htt aggregates was demonstrated in cultured hippocampal neurons cells expressing a mutant htt fragment. Dendrites in hippocampal neurons became dystrophic around enlarged amphisome-like structures positive for Rab11, LC3 and mutant htt aggregates. Furthermore, Rab11 overexpression rescues neurodegeneration and dramatically extends lifespan in a Drosophila model of HD. Our findings are consistent with the model that mutant htt aggregation increases local autophagic activity, thereby sequestering Rab11 and diverting spine-forming cargo from RE into enlarged amphisomes. This mechanism may contribute to the toxicity caused by protein misfolding found in a number of neurodegenerative diseases.
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