What are grana in chloroplasts of vascular plants good for?

Abstract

All plants and green algae contain stacked grana thylakoid membranes in their chloroplasts, underscoring an evolutionary pressure to maintain this unique structural feature. Furthermore, numerous studies demonstrate that particular lateral and vertical dimensions of grana facilitate the function, regulation, and repair of the photosynthetic machinery responsible for energy conversion. In this review, we present an updated overview of our understanding concerning the structure of grana thylakoids, the forces that contribute to their formation, and their architectural dynamics. After establishing the structural foundation, we will continue reviewing the implications of grana formation on light harvesting, electron transport, and protein maintenance in the thylakoid membranes of vascular plants. Regarding light harvesting, this review will discuss the implications of grana formation on energy spillover, macromolecular crowding, lateral versus vertical excitation energy transfer, and state transition. With respect to electron transport, we will summarize recent findings regarding the functional connectivity of spatially separated photosystems facilitated by grana formation through small mobile electron carriers. Furthermore, we will explore how the dynamic responses of grana architecture regulate electron transport. Finally, we will address how grana formation contributes to the organization of protein repair and biogenesis within thylakoid membranes.