Figure 2.

Physiological responses to sunflecks perceived by UVR8. A to F, Hypocotyl length of mutant and wild-type plants relative to control plants in shade plotted against the UV-B photon flux density received under sunfleck conditions (A) or against the duration of the sunfleck (B–F). Seedlings were grown under deep shade for 3 d, followed by 5 d of deep shade interrupted daily by a sunfleck at midday. In A, 30-min sunflecks were provided by canopies of different height or unfiltered sunlight. In B, sunflecks of the indicated duration were provided by full sunlight. Data are means ± se of at least three biological replicates (B, C, E, and F, the same Col-0 control was used to aid the comparison). Significant differences (regression analysis) in slope of response are indicated. G to I, CHS expression (G) and CHS protein abundance (H and I). Seedlings were grown outdoors under a dense canopy for 7 d, transferred at midday to sunfleck conditions, and harvested 2 h later. CHS level in seedlings of the Col-0 wild type and of the uvr8, rup1 rup2, phyA, phyB, cry1, and cry2 mutants. Data are means ± se of at least three biological replicates and the significance of the interaction between uvr8 (G) or the indicated photoreceptor mutant (H) and sunfleck is indicated (regression analysis). I, Representative protein gel blots show the effects of uvr8 (upper panel) or cry1 (lower panel). The uvr8-7 allele (Ws) was used in A, D, and G, whereas the uvr8-6 allele (Col-0) was used in E, H, and I.