Figure 3.

UV-B Inhibits PIF4 Transcript Accumulation in a UVR8-Dependent Manner and Promotes PIF4 Degradation in a Temperature-Conditional Manner

(A) PIF4-HA abundance in 35S:PIF4-HA seedlings grown for 10 days in 16 hr light/8 hr dark cycles at 20°C, harvested before dawn and 2 hr after dawn following transfer to the stated conditions. Col-0 serves as a negative control. Ponceau stain of Rubisco large subunit (rbcL) serves as a loading control.

(B) Time course of plants grown and treated as in (A). Relative protein abundance was normalized to Ponceau staining of the Rubisco large subunit, then expressed as a value relative to pre-dawn levels (n = 3; ±SE). Asterisks denote a significant difference between UV-B- and white light (WL)-treated controls at their respective temperatures.

(C) PIF4 transcript abundance in Ler and uvr8-1 seedlings grown as in (A) and harvested at 4 hr (^∗significant UV-B-mediated decrease in transcript abundance when compared to 20°C, p < 0.05; ^∗∗significant UV-B-mediated decrease in transcript abundance when compared to 28°C, p < 0.05).

(D) Representative blot showing PIF4 abundance in Ler grown as in (A) at the 2 hr time point using anti-PIF4 antibody. Ponceau stain of Rubisco large subunit (rbcL) serves as a loading control.

(E and F) Time course of PIF4 transcript abundance. Seedlings were grown for 10 days in 8 hr light/16 hr dark cycles at 20°C. On day 11, plants were transferred to either (E) 20°C or (F) 28°C ± UV-B. UV-B treatment was maintained for the duration of the photoperiod and plants harvested at the times shown. All values are normalized to time 0. The mean of two biological repeats are shown ± SD.

See also Figures S2 and S3.