Membrane lipid properties in photosynthetic responses to environmental changes

Oxygenic photosynthesis relies on multisubunit protein complexes embedded in the thylakoid membrane, which is distinguished by its unique lipid composition consisting of galactolipids and sulfolipids together with phosphatidylglycerol rather than typical phospholipids. Emerging structural and biophysical evidence indicates that these lipids are involved in dynamic regulation of photosynthesis. Lipids act as structural cofactors to stabilize the assembly of photosystem complexes and also as modulators of membrane properties such as fluidity, polymorphism, and thickness, which directly impact photosynthetic processes. These physical properties of the thylakoid membrane are regulated according to environmental conditions. Fatty acid unsaturation modifies lipid bilayer fluidity and thereby mitigates the effects of temperature on membranes. The ratio of non-bilayer-forming to bilayer-forming lipids contributes to lipid phase transitions required for environmental responses of thylakoid proteins. Furthermore, changes in thylakoid membrane thickness regulate protein-protein assembly, such as the aggregation of light-harvesting complex II through hydrophobic mismatch, thereby modulating the light-harvesting system. In this review, we integrate recent findings to highlight the role of thylakoid lipids as modulators of photosynthetic protein interactions and their conformational and functional states, providing key insights into the functional regulation of the photosynthetic apparatus in response to environmental changes.