Chapter 9: Regulatory Control of Antenna Function in Plants

This chapter first introduces photosynthetic light-harvesting antenna systems in the context of the evolutionary path of photosynthetic organisms from anoxygenic bacteria to cyanobacteria to algae and higher plants. The introduction continues by explaining the main regulatory mechanisms used by higher plants to adapt and acclimate to their environment. The focus of this chapter is the main regulatory “feedback” mechanism of higher plants, which involves the recently recognized role of the PsbS protein in thermal dissipation of excess energy in Photosystem II (PSII). A quantitative molecular model is presented to define this vital energy dissipation process. The model is based on the results of recent studies that have advanced our understanding and is focused on four major developments: (1) molecular control of the structure–function of the PsbS protein with respect to its role in dissipating excess light-energy; (2) molecular control of the content of all chlorophyll b containing light-harvesting proteins (Lhcbs) of the “peripheral” and “proximal” PSII antenna; (3) time and wavelength dependent resolution of the flow of energy in the PSII antenna system at cryogenic temperatures; and (4) assessment of the photoprotective capacity and physiological significance of PsbS-dependent energy dissipation. Our contemporary model of PSII antenna control takes into consideration the respective roles of the peripheral and core-inner antennae pigment–proteins of PSII. We conclude by outlining obvious plans for future further studies aimed at understanding and controlling the regulation of excess light acclimation in PSII.