Functional analysis of the period and timeless circadian molecular mechanism within the diptera

In D. melanogaster the period (per) and timeless (tim) genes form a feedback loop that rhythmically inhibits their own transcription. This mechanism creates a twenty four hour clock that regulates many of the flies behavioural and molecular circadian cycles. The conservation of at least per as part of this molecular mechanism in mammals suggests that clock gene functions are well conserved across the animal kingdom. However analysis of per and tim functions in Antherea pernyi and Musca domestica illustrated that the function of the genes did not comply with the D. melanogaster feedback model, and that the genes functions may have diverged significantly within the insects.;To further test this divergence of function, analysis of the per and tim function was performed on D. virlis and D. pseudoobscura and extended in Musca. The functional analysis confirmed that Musca PER does not obeying the D. melanogaster circadian clock model. In particular it does not cycle in abundance or subcellular localisation. Furthermore the timing cycles of per and tim transcripts are significantly different between D. virilis and D. pseudoobscura and D. melanogaster. Furthermore unusual PER and TIM cycles in D. virilis suggest that it may have a quite different method of generating a twenty four hour cycle. All of which suggests that the genetic mechanisms behind the molecular clocks of the insects have undergone widespread changes over evolutionary history, and may mean that they are a target for change during speciation events.