Abstract
We previously reported that we tried to make bioluminescence reporters of nuclear clock genes to monitor circadian rhythmicities in the activities of the clock gene promoters in the unicellular green alga Chlamydomonas and that we encountered the problem. Two luciferase bioluminescence reporter strains having promoter regions of the clock genes ROC15 and ROC75, respectively, whose mRNA levels oscillate with an 8-hour phase-angle-difference, showed the circadian rhythms of luciferase mRNA levels oscillating with a phase-angle-difference similar to that of endogenous ROC15 and ROC75 mRNAs. But contrary to our expectations, they showed the bioluminescence rhythms with the same phase. Here, we report the results of analyses of the luciferase protein levels in the two clock gene reporter strains, and of effects of culture conditions and host strains on the bioluminescence rhythm. These analyses revealed that circadian rhythmicities of luciferase reporters are regulated at posttranscriptional steps in Chlamydomonas.
