Temporal and spatial expression of the period gene in the reproductive system of the codling moth

The authors examined patterns of spatial and temporal expression of Drosoph ila per gene homologue in the codling moth, Cydia pomonella. Since sperm re lease in moths is regulated in a circadian manner by an autonomous clock th at is independent from the brain, the authors investigated per expression i n male reproductive system along with its expression in moth heads. per mRN A is rhythmically expressed with the same phase and amplitude in both tissu es under light-dark (LD) conditions. The levels of per mRNA are low during the day, start to increase before lights-off, reach the peak in dark, and d ecrease after Lights-on. Ln constant darkness (DD), cycling of per mRNA con tinued in heads with severely blunted amplitude. No cycling of per mRNA was detected in testis in DD. In situ hybridization and immunocytochemistry re vealed distinct spatial patterns of per expression in the moth reproductive system. There is no expression of per in cells forming the wall of testes or in sperm bundles. However, per mRNA and protein are rhythmically express ed in the epithelial cells forming the wall of the upper vas deferens (UVD) and in the cells of the terminal epithelium, which are involved in the cir cadian gating of sperm release. Increase in per mRNA in the UVD coincides w ith sperm accumulation in this part of the insect reproductive system.