The Cytochrome b 6 f Complex: A Regulatory Hub Controlling Electron Flow and the Dynamics of Photosynthesis?

Chapter 22; Photosynthetic organisms must respond to several external stimuli to adjust their photosynthetic performances in order to keep a high capacity of carbon assimilation and avoid photodamage. They do so integrating processes occurring at different time scales starting from very fast light harvesting, down to slow changes of electron flow and protein composition of the photosynthetic apparatus. Central to these regulatory mechanisms is the cytochrome b(6)f complex, which regulates intersystem electron flow via photosynthetic control and modulates light harvesting capacity by acting as a redox sensor to trigger an acclimation process named state transitions. In this chapter we describe how the cytochrome b(6)f complex performs to regulate these different functions in both plants and microalgae, proposing new mechanisms of regulation, and critically discussing how these processes are compatible with the existing literature on the structure and function of this complex.