Figure 1.

Continuous Light-Induced Second Positive Phototropism in the rpt2 Mutants and the RPT2 Overexpression Line.

(A) Time-course analysis of continuous light-induced phototropism. Two-day-old dark-grown seedlings (Columbia [Col; circles], rpt2-2 [triangles], rpt2-2 transgenic plants harboring 35S_pro:RPT2 [35S; squares], and rpt2-1 [diamonds]) were pretreated with (red symbols) or without (black symbols) overhead red light (RL) at 20 μmol m^–2 s^–1 for 2 min. The hypocotyls were then irradiated with unilateral blue light (BL) at 0.17 μmol m^–2 s^–1 for 6 h, during which time the hypocotyl curvatures were determined at 10-min intervals. The data shown are means ± se from eight seedlings.

(B) Effects of light irradiation on levels of RPT2. Dark-grown seedlings were pretreated with (top panel) or without (bottom panel) overhead red light for 2 min. After 2 h, seedlings were continuously irradiated with unilateral blue light at 0.17 or 0.0017 μmol m^–2 s^–1. The shoots were harvested at the indicated time points and used to prepare crude microsomal insoluble proteins. Proteins (6 μg) in each fraction were separated on 7.5% SDS-PAGE gels, followed by immunoblotting with anti-RPT2 and anti-PHOT1 antibodies. Time 0 corresponds to the onset of unilateral blue light treatment.

(C) Time-course analysis of continuous light-induced phototropism at 0.0017 μmol m^–2 s^–1. The data shown are means ± se from eight seedlings. Other details are as described in Figure 1A.

(D) Hypocotyl phototropism induced by strong blue light. Dark-grown seedlings were irradiated with unilateral blue light for 6 h at 1, 10, and 100 μmol m^–2 s^–1. The data shown are means ± se from 10 seedlings.