FIGURE 2.

Diversity of PSI-LHCI supercomplexes and PSI core subunits deriving from oxygenic photosynthesis organisms. (A) Different PSI-LHCI from oxygenic photosynthesis organisms. Light-harvesting antenna Lhcrs and the core subunit PsaO are appeared in red algae. In the second endosymbiosis event, the core subunits PsaS, PsaR and light-harvesting antenna FCPIs are appeared in diatoms, whereas PsaK and PsaO are not found in diatoms. The light-harvesting antenna Lhcas (8 or 10) and the core subunits PsaG, PsaH, and PsaO are appeared in green algae (C. reinhardtii and B. corticulans), except for the mini-PSI from Dunaliella salina which contains seven core subunits and four Lhcas. PsaX is lost in all photosynthetic eukaryotes. The peripheral light-harvesting antenna of PSI is simplified in bryophytes and vascular plants, and the core subunit PsaM of PSI is lost, but PsaN is appeared in plant PSI. LHCII binds to the PSI-LHCI supercomplex when the state transition occurs in green algae, bryophytes, and vascular plants. (B) Structure of the special PSI core subunits from different photosynthetic organisms: transmembrane core subunits—PsaX, PsaG, PsaK, PsaO, PsaR, and PsaN, and non-transmembrane core subunit —PsaS. Color codes used are as follows (PsaA, PsaB, PsaC, PsaD, PsaE, PsaF, PsaI, and PsaK are uniformly represented in gray because they are relatively conserved in the positions of different species): PsaX, purpleblue; PsaG, hot pink; PsaH, ruby; PsaK, light blue in panel (B); PsaM, yellow; PsaN, yellow-orange; PsaO, deep teal; PsaS, purple; PsaR, orange; FCPIs, green; LHCII, limon; lhcr/lhca, palegree.