Physiological and evolutionary implications of tetrameric photosystem I in cyanobacteria

Meng Li (1) , Alexandra Calteau (2) , Dmitry Semchonok (3) , Thomas Witt (1) , Jonathan Nguyen (1) , Nathalie Sassoon (4) , Egbert Boekema (3) , Julian Whitelegge (5) , Muriel Gugger (4) , Barry Bruce (1)

1 The University of Tennessee [Knoxville]
2 LABGeM - Analyse Bio-Informatique pour la Génomique et le Métabolisme
3 University of Groningen [Groningen]
4 Collection des Cyanobactéries
5 David Geffen School of Medicine [Los Angeles]

Photosystem I (PSI) is present as trimeric complexes in most characterized cyanobacteria and as monomers in plants and algae. Recent reports of tetrameric PSI have raised questions regarding its structural basis, physiological role, phylogenetic distribution and evolutionary significance. Here, we examined PSI in 61 cyanobacteria, showing that tetrameric PSI, which correlates with the psaL gene and a distinct genomic structure, is widespread among heterocyst-forming cyanobacteria and their close relatives. Physiological studies revealed that expression of tetrameric PSI is favoured under high light, with an increased content of novel PSI-bound carotenoids (myxoxanthophyll, canthaxanthan and echinenone). In sum, this work suggests that tetrameric PSI is an adaptation to high light intensity, and that change in PsaL leads to monomerization of trimeric PSI, supporting the hypothesis of tetrameric PSI being the evolutionary intermediate in the transition from cyanobacterial trimeric PSI to monomeric PSI in plants and algae.

Domains: Life Sciences [q-bio]

Meng Li, Alexandra Calteau, Dmitry Semchonok, Thomas Witt, Jonathan Nguyen, et al.. Physiological and evolutionary implications of tetrameric photosystem I in cyanobacteria. Nature Plants, 2019, 5 (12), pp.1309-1319. ⟨10.1038/s41477-019-0566-x⟩. ⟨pasteur-03016132⟩