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 to
investigate 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 candidates
belong to the SPFH protein family, implicated in vesicular lipid transport and already
associated with thylakoid maintenance under hight light conditions, and the DedA protein
family, which has been associated with lipid rearrangement. Furthermore, the structural
prediction of proteins involved in the assembly of the ETC highlight structural differences in
the YidC translocase between the Gloeobacterales and thylakoid-bearing cyanobacteria that
may have facilitated the targeting of thylakoid-associated proteins.