Fig. 3.

Regulation of electron transport pathways. A, Confocal microscopy images show different localization of functional NDH-1 complexes in Synechococcus 7942 grown in moderate light (60 μE m^− 2 s^− 1) and low light (6 μE m^− 2 s^− 1). The fluorescence of green fluorescence proteins (shown in green) revealed the distribution of NDH-1 complexes, whereas chlorophyll fluorescence (shown in red) indicates the location of thylakoid membranes. The reorganization of NDH-1 complexes in thylakoid membranes highly correlates with the direction of electron flow to respiratory pathway or photosynthetic pathway. For details, see [19]. B, Model of the regulation of electron transport pathways in cyanobacterial thylakoid membranes. Arrows indicate the directions of electron flow. Complexes related to photosynthesis are shown in green and respiratory components are indicated in blue. Different light intensities could trigger the variation of the redox state of PQ pool, and thereby lead to distinct pathways of electron transport.