Thylakostasis: key factors in thylakoid membrane organization with emphasis on biogenesis and remodeling proteins in vascular plants.

The thylakoid membrane (TM), a defining feature for almost all oxygen-evolving photosynthetic organisms, serves as the structural foundation for light-driven energy conversion. In vascular plants, the TM evolved into a complex architecture composed of single-layered stroma thylakoids and stacked grana thylakoids, enabling the spatial organization of two photosystems (PSII and PSI) to optimize light capture and energy transfer. In addition, two membrane regions, one connecting these two compartments (grana margin) and the other corresponding to the curvature domain in grana, function in dissipating excess energy, balancing electron transfer, and maintaining functional PSII. Recent advances in electron microscopy imaging and proteome analysis of membrane subcompartments have provided new insights into the structure and dynamic adaptations of the TM in response to diverse environmental conditions. To describe the mechanisms that govern TM architecture, dynamics, and integrity, I am introducing the concept of "thylakostasis" (thylakoid homeostasis). Here, I provide an overview of the molecular components and processes central to thylakostasis, including the biosynthesis of lipids, chlorophyll, and proteins. I focus particularly on the membrane remodeling proteins whose functions have been elucidated recently, such as VIPP1, a member of the evolutionarily conserved PspA/ESCRT-III superfamily; FZL, a dynamin-like GTPase; and CURT1, a curvature-inducing protein unique to photosynthetic organisms. Together, these factors orchestrate TM biogenesis, remodeling, and adaptive flexibility that is essential for photosynthetic efficiency.