Malfunction of circadian clock in the non-photoperiodic-diapause mutants of the drosophilid fly, Chymomyza costata

The diel rhythmicity of adult eclosion was recorded in reciprocal F1 hybrids between the wild-type (Sapporo) and mutant (NPD) strains of Chymomyza costata and the functionality of central circadian clocks was checked in both strains by assessing diel and circadian patterns of the per gene mRNA abundance oscillations in fly heads using competitive polymerase chain reaction methodology. The previously detected mutations in the per coding region of the NPD strain (Shimada, Entomol. Sci. 2 (1999) 575) were found to be primarily neither responsible for the loss of the eclosion rhythm nor for the malfunction of the circadian clocks. While distinct diel and circadian rhythms in per mRNA abundance were found in the wild-type flies, the npd-mutants showed constant (arrhythmic) and low abundance of the per mRNA transcripts. Because the non-photoperiodism, arrhythmicity of adult eclosion and the malfunction of central circadian clocks all seem to result from a mutation in the autosomal npd locus, we hypothesize, that a product coded by this locus may represent a ‘point of contact’ between the circadian and photoperiodic time measurement systems in C. costata.