RNA interference of timeless gene does not disrupt circadian locomotor rhythms in the cricket Gryllus bimaculatus

Molecular studies revealed that autoregulatory negative feedback loops consisting of so-called clock genes constitute the circadian clock in Drosophila However this hypothesis is not fully supported in other Insects and is thus to be examined In the cricket Gryllus bimaculatus we have previously shown that period (per) plays an essential role in the rhythm generation In the present study we cloned cDNA of the clock gene timeless (rim) and investigated its role in the cricket circadian oscillatory mechanism using RNA interference Molecular structure of the cricket tim has rather high similarity to those of other insect species Real-time RT-PCR analysis revealed that rim mRNA showed rhythmic expression in both LD and DD similar to that of per peaking during the (subjective) night When injected with rim double-stranded RNA (dstim) tim mRNA levels were significantly reduced and its circadian expression rhythm was eliminated After the dstim treatment however adult crickets showed a clear locomotor rhythm in DD with a free-running period significantly shorter than that of control crickets injected with Discosoma sp Red2 (DsRed2) dsRNA These results suggest that in the cricket rim plays some role in fine-tuning of the free-running period but may not be essential for oscillation of the circadian clock (C) 2010 Elsevier Ltd All rights reserved