Figure 1.

Arabidopsis protoplasts maintain a robust free-running rhythm with approximately 24-h period for over 6 d. A and C, Bioluminescence traces from protoplast cells transfected with CCA1-LUC plasmids. B and D, Bioluminescence traces from protoplast cells transfected with GI-LUC plasmids. Protoplasts were prepared from rosette leaves of 25- to 35-d Arabidopsis plants of the appropriate wild-type (Col) or mutant (elf3-1, toc1-101, and ztl-3) genotypes grown under a 12-h-light/12-h-day cycle and transfected with the reporter plasmid indicated. After transfection protoplasts were transferred to constant red light (14 μmol m⁻² s⁻¹) at ZT9 (n = 6; mean ± SEM). Image acquisition was performed every 2 h for 6 d. Each data set was normalized to the mean expression level over the 24- to 144-h sampling schedule. White and gray regions indicate subjective light and dark period. Similar results were obtained in two independent trials.