Spatial and circadian regulation of cry in Drosophila

In Drosophila, cryptochrome (cry) encodes a blue-light photoreceptor that mediates light input to circadian oscillators and sustains oscillator function in peripheral tissues. The levels of cry mRNA cycle with a peak at approximately ZT5, which is similar to the phase of Clock (Clk) mRNA cycling in Drosophila. To understand how cry spatial and circadian expression is regulated, a series of cry-Gal4 trans-genes containing different portions of cry upstream and intron 1 sequences were tested for spatial and circadian expression. In fly heads, cry upstream sequences drive constitutive expression in brain oscillator neurons, a novel group of nonoscillator cells in the optic lobe, and peripheral oscillator cells in eyes and antennae. In contrast, cry intron 1 drives rhythmic expression in eyes and antennae, but not brain oscillator neurons. These results demonstrate that intron 1 is sufficient for high-amplitude cry mRNA cycling, show that cry upstream sequences are sufficient for expression in brain oscillator neurons, and suggest that cry spatial and circadian expression are regulated by different elements.