Results of Dolezelova et al.6 and Kaushik et al.14

Figure 1 | Results of Dolezelova et al.6 and Kaushik et al.14 Results of
Dolezelova et al.6 and Kaushik et al.14. The vertical axis is the mean free-running
circadian period in hours under constant conditions (constant dark unless otherwise
stated); the horizontal axis is the experimental temperature in °C. These
experiments directly implicate a role for cryptochrome in temperature insensitivity
mechanisms. Dolezelova et al.6 generated a full CRY knockout mutant (CRY0)
revealing that these mutants behaved in an anomalously rhythmic manner in
constant light. This is a distinctly non-wild-type behaviour, which occurs due to
the lack of constant photic-input (because CRY is absent) to the circadian system
in such knockouts. Moreover, this circadian behaviour was revealed to be
anomalously temperature sensitive. However, in constant darkness, the circadian
system revealed a re-establishment of temperature insensitivity. This reveals
two independent mechanisms of temperature insensitivity in Drosophila – 1) a
light/cryptochrome-dependent mechanism, and 2) a “dark”/cryptochrome-independent
mechanism. The authors concluded that the results suggest a role for
CRY beyond the classical Drosophila model, and that the gene is involved in
core pacemaking. Further knockout studies (Kaushik et al) involved the longrunning
period mutant perL alongside the loss of function cryptochrome mutant
CRYb. The results revealed that whilst the CRYb retained temperature insensitivity,
the CRYb. mutant was capable of restoring the temperature-sensitive phenotype
of perL mutants. The authors suggest that the interaction of CRY and PER-TIM
are responsible for temperature insensitivity, and that conclude that “interaction
between CRY and PER-TIM complex is responsible for the loss of temperature
compensation in the perL strain”6.

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