Figure 2.

Brassinosteroid (BR) signal increases in the dark. (a) Phenotypes of 7-day-old 35Spro:BZR1-HA and phyB-78 35Spro:BZR1-HA seedlings, and the corresponding (b) protein gel blot. The numbers indicate the ratio of dBZR1 to pBZR1. (c) qRT-PCR analysis of GER1, PRE5 and PRE6 in Ws-2 and phyB-77 seedlings grown under red light for 5 days with a photon fluence rate of 80 μmol m⁻² s⁻¹ at 22°C. (d, e) Protein gel blots showing the abundance of the phosphorylated (pBZR1) and dephosphorylated (dBZR1) forms of BZR1 in different light conditions. (d) Seedlings (7 days old) expressing BZR1pro:BZR1-HA were subjected to various conditions: L, continuous light; LD, continuous light followed by transfer to dark for 6 h; BL, brassinolide treatment; LDL, transfer to darkness for 6 h and subsequently to light for 6 h with a photon fluence rate of 80 μmol m⁻² s⁻¹ at 22°C. (e) 35Spro:BZR1-HA seedlings were grown in continuous light for 7 days with a photon fluence rate of 103 μmol m⁻² s⁻¹, and were transferred to darkness for 1–24 h, as indicated. In both panels, actin was used as an equal loading control and the numbers indicate the ratio of dBZR1 to pBZR1. (f) qRT-PCR analysis of the expression of CHALCONE SYNTHASE (CHS), ACS5, GER1, PRE5, PRE6 and CPD in 10-day-old plants grown under continuous light (cL), light followed by darkness for 12 h (LD12) or light transferred to darkness for 12 h and back to light for 12 h (LD12 → L12). The photon fluence rate during light treatment was 103 μmol m⁻² s⁻¹. Error bars in (c) and (f) are standard deviations (n = 3).