Daily Expression Patterns of Cycle and Clock Genes in the Head of the Silkworm, Bombyx Mori

ABSTRACT

Clock and cycle (Bmall) genes encode the basic helix-loop-helix-PAS (Period-Aryl-hydrocarbon receptor-Singleminded) proteins that function as transcription factors regulating the transcription/translation-based autoregulatory feedback in the circadian clock of many organisms. In the present study we examined the temporal pattern in the expression of mRNA of Clock (BmClk) and Cycle (BmCyc) genes in the head of Bombyx mori by Northern blot analysis. BmClk gene was co-expressed in the same tissues as those where BmCyc was expressed. In a daily light-dark cycle BmCyc did not show significant difference in expression. Surprisingly unlike the case of Drosophila melanogaster, the levels of BmClk transcript exhibited no prominent circadian oscillation in the moth head. This casts a doubt that the structure and regulatory mechanism of circadian clock may not be uniform among organisms.