Cytoplasmic Membrane to Thylakoids: Evolution of Membrane Biogenesis and Photosystem II assembly in early- diverging Cyanobacteria

Cyanobacteria are prokaryotic microorganisms that perform oxygenic photosynthesis, producing oxygen as a byproduct, through an electron transport chain (ETC) embedded in specialized intracellular membranes known as thylakoids. While most Cyanobacteria possess thylakoid membranes, the Gloeobacterales—the earliest-diverging clade within Cyanobacteria—lack thylakoid structures, indicating that their photosynthetic ETC is embedded within specialized regions of the plasma membrane. In thylakoid-bearing cyanobacteria, thylakoid membrane biogenesis provides the structural and regulatory framework for ETC assembly, ensuring spatial and temporal coordination of photosynthetic complex integration.
By combining membrane biogenesis mechanisms and phylogenetic reconstruction, we aim toinvestigate the evolutionary emergence of thylakoid membranes. We performed a
phylogenomic analysis of the genes involved in membrane dynamics, identifying three
candidate proteins associated with membrane trafficking that may contribute to thylakoid
biogenesis based on their taxonomic distribution and structural predictions. These candidatesbelong to the SPFH protein family, implicated in vesicular lipid transport and alreadyassociated with thylakoid maintenance under hight light conditions, and the DedA proteinfamily, which has been associated with lipid rearrangement. Furthermore, the structuralprediction of proteins involved in the assembly of the ETC highlight structural differences inthe YidC translocase between the Gloeobacterales and thylakoid-bearing cyanobacteria thatmay have facilitated the targeting of thylakoid-associated proteins.