Figure 2.

Morning-phased BBX19 and BBX18 are involved in regulating self-sustained circadian period. A, B, Increased expression of BBX18 or BBX19 lengthened the circadian period length. The full-length gene constructs of BBX18:BBX18 and BBX19:BBX19 were transformed into the wild-type plants to generate the overexpression transgenic lines. Period estimation for of individual CCA1:LUC rhythm (A) is plotted against their relative amplitude errors (RAEs) (B). RAE is used to define the limit of rhythmicity, a complete sine-fitting wave is defined as 0, and a value of 1 defines the weakest rhythm. Data represent mean ± se from three independent experiments. At least 24 individual seedlings were used for each analysis. Open bars indicate subjective day, and gray bars indicate subjective night. C, D, Circadian rhythm (C) and period estimate (D) of the bbx18 bbx19 double mutant under free-running conditions. The bbx18-2 bbx19-3, together with Col-0 and bbx19-3 seedlings were entrained under 12-h:12-h LD cycles for 2 weeks and then released to constant light (LL) at 22°C for 5 days. E, F, The daily expression of BBX18 and BBX19 proteins were regulated by the circadian clock, with a peak phase appeared in the morning. The CT phase angles for individual seedlings were plotted against their RAE values to indicate the peak position and the robustness of rhythmicity, respectively (F)