Unravelling the function of the novel gene, day, in Drosophila melanogaster

Circadian rhythms in biological outputs are seen in numerous phyla that live in cyclical environments. Regulation of these behaviours has been examined in the fruit fly Drosophila melanogaster, with many of its genes sharing mammalian homologs. One component of the molecular clockwork of particular interest is the light activated cryptochrome (cry) gene; cry has been shown to be important for a number of light driven behavioural outputs, including but not limited to: entrainment, response to brief light pulses, sensitivity to magnetic stimulus and negative geotaxis. A yeast two hybrid screen (hybrigenics) revealed cry associating with a novel gene primarily in darkness; the gene CG15803 displayed a light dependent binding to CRY and was re-named DAY (Dark Active in Yeast). The goal of this research was to characterise DAY and examine the consequences of DAY-CRY binding on behavioural rhythmicity, as well as further examine the influence of cry’s C-terminus in regulating its function. This was accomplished using unique transgenic constructs aimed at: removing day, cloning tagged versions of day cDNA for protein work, creating day promoter lines which give information on its cellular location and examining behaviour of cry C-terminus mutants. Using this methodology uncovered a number of phenotypes for flies lacking day and hints at a possible role for day in regulating cry in one particular clock cell. The mutation of the C-terminus of cry’s revealed some residues important for regulation of cry.