Figure 4.

BBX22 protein functions in the inhibition of hypocotyl elongation under SD conditions. A, The bbx22 mutant is hyposensitive to light only under SD conditions. Hypocotyl length was measured for 4-d-old seedlings grown under SD or LD conditions. * P < 0.01, Student’s t test; n = 38 to 76. B, BBX22 protein accumulates to a higher level in SD-grown Col plants (SD; white triangles, solid lines) compared with that in plants under LD conditions (white circles, dashed lines). BBX22 protein levels at different times of the day were determined by immunoblot analysis. Results are presented as values relative to that at dawn for 4-d-old seedlings grown under LD conditions. White bars indicate light periods and black bars indicate dark periods. n = 4. AUC, Areas under the SD or LD protein curves. C, bbx22 shows an increased growth rate during the dark period of SD conditions, with the most noticeable difference at day 4 after germination. Time 0 indicates dawn of day 4 after germination. Shaded and black areas indicate night (darkness), and white areas indicate day (lights on). Shaded areas around each growth trace (blue and red) show se. n = 29.