Abstract
The pex (period extender) gene is a negative regulator of kaiA gene, an essential gene for circadian clock. The expression of pex gene was induced by light-dark transition. This suggested that pex gene had a certain role in light-dark cycle. Previously we compared the phase of circadian rhythm in wild-type and pex-inactivated mutant cultivated in the continuous light condition, but the remarkable difference was not observed. In this time, we report that pex-inactivated mutant cultivated in light-dark cycles notably advanced in the phase for 3 hours compared with the one in wild type. Under this light-dark condition, the growth rate and the color of colonies were the same between the wild-type and the pex-inactivated mutant. It seemed to be concluded that pex gene was a gene in the input pathway which modulate the circadian phase.
