Chloroplast redox signals: How photosynthesis controls its own genes

The photosynthetic apparatus of higher plants and algae is composed of plastid- and nuclear-encoded com-ponents, therefore the expression of photosynthesis genes needs to be highly coordinated. Expression is regulated by various factors, one of the most import-ant of which is light. Photosynthesis functions as a sensor for such light signals, and the redox state of photosynthetic electron transport components and redox-active soluble molecules act as regulating para-meters. This provides a feedback response loop in which the expression of photosynthesis genes is coupled to the function of the photosynthetic process, and high-lights the dual role of photosynthesis in energy fixation and the reception of environmental information. In higher plants and algae, photosynthesis takes place i