Figure 1.

Monitoring of NDH activity using chlorophyll fluorescence analysis. A, Schematic model of NDH function. The NDH complex functions in electron transport from an unidentified electron donor, possibly NAD(P)H or ferredoxin (Fd) to PQ. PQ reduction was monitored by chlorophyll fluorescence emitted from PSII. PQ reduction in the dark depends on NDH activity and can be monitored as a transient increase in chlorophyll fluorescence after AL illumination. PC, Plastocyanin; FNR, ferredoxin-NADP⁺ oxidoreductase. B, Analysis of the transient increase in chlorophyll fluorescence after turning off AL. The bottom curve indicates a typical trace of chlorophyll fluorescence in the wild type (WT). Leaves were exposed to AL (50 μmol photons m⁻² s⁻¹) for 5 min. AL was turned off and the subsequent change in chlorophyll fluorescence level was monitored. Insets are magnified traces from the boxed area. The fluorescence levels were normalized by F_m levels. ML, Measuring light; SP, saturating pulse of white light; crr6 + CRR6, crr6 complemented by introduction of the wild-type genomic CRR6.