Figure 5.

Fd-Dependent PQ Reduction Assay in Ruptured Chloroplasts.

(A) Increases in the chlorophyll fluorescence, by the addition of NADPH (250 µM) and Fd (5 µM) under a weak light (1.0 µmol photons m^–2 s^–1), were monitored in ruptured chloroplasts (20 µg chlorophyll mL^–1) from the wild type in the absence (– recTrx) or presence (+ recTrx) of reduced Trx m proteins. Ruptured chloroplasts were incubated with 5.0 µM of the prereduced Trx m before the measurement. The fluorescence levels were standardized by the Fm levels.

(B) Trx isoform-specific suppression effect on the Fd-dependent PQ reduction in ruptured chloroplasts from the wild type. Activity of Fd-dependent PQ reduction was evaluated using the equation (F – Fo)/(Fm – Fo) (Figure 5A; Supplemental Figures 4A and 4B). Each value represents the mean ± sd of four to six independent chloroplast preparations. Columns with the same letters are not significantly different between genotypes (Tukey–Kramer test, P < 0.05).

(C) Effect of the reduced Trx m on the Fd-dependent PQ reduction in ruptured chloroplasts from the crr2-2 and pgr5 mutants. Prereduced Trx m1 (5.0 µM) was added to ruptured chloroplasts before the measurement. WT, wild type.