Expression of ClkDN.Scer\UAS in the fat body (under the control of Scer\GAL4to.PD) dampened the cycling of tim and a number of metabolic genes. These flies display locomotor activity rhythms similar to those of control flies. However, the phasing of the feeding rhythm in DD is different to that of control flies, with the trough limited to a small period during the day (CT4-6), and the peak appears in the early night time and lasts until the following day. Similar results are obtained when the CAFE assay is used to measure the feeding rhythm. The change in the feeding curve suggests that clock in metabolic tissues, most likely in the fat body, regulate the phase of the feeding rhythm.
Expression of ClkDN.Scer\UAS by the general olfactory receptor cell driver Scer\GAL4Or83b.2.642.T:Hsim\VP22 eliminates the olfactory rhythm. These flies display feeding rhythms on the third day in DD with a phase similar to that of control flies.
Expression of ClkDN.Scer\UAS in the fat body (under the control of Scer\GAL4to.PD) results in higher total food consumption. Comparison of the amount of food consumed in 2-hour blocks at different circadian times between control flies and flies lacking Clk in metabolic tissues reveals that the increase in feeding is more dramatic during the subjective night time. Flies lacking Clk in the olfactory neurons (expression of ClkDN.Scer\UAS under the control of Scer\GAL4Or83b.2.642.T:Hsim\VP22) exhibit decreased total food consumption compared to control flies.
Expression of ClkDN.Scer\UAS in the adult female fat body (Scer\GAL4yolk) disrupts the fat body clock and results in dramatically reduced survival in response to starvation in virgin female flies. However, male flies carrying ClkDN.Scer\UAS and Scer\GAL4yolk do not display increased sensitivity to starvation.
Flies carrying ClkDN.Scer\UAS under the control of the drug-inducible fat body driver Scer\GAL4S106-GS show increased sensitivity to starvation only when they are treated with mifepristone (RU486) from the first instar larval stage onwards.
Glycogen levels are extremely low in flies in which ClkDN.Scer\UAS is expressed under the control of Scer\GAL4to.PD or Scer\GAL4yolk. In contrast, male flies carrying Scer\GAL4yolk and ClkDN.Scer\UAS do not display such a phenotype. Lipid storage is only slightly decreased in these flies.
Expression of ClkDN.Scer\UAS in the fat body, under the control of Scer\GAL4to.PD in a cyc01 background fails to affect starvation sensitivity. Glycogen levesl are lower than those of cyc01 flies, but the decrease is less than that seen in heterozygous cyc01 flies with a disrupted fat body clock.
