Time-resolved comparative molecular evolution of oxygenic photosynthesis

Area of Science:

• Biochemistry
• Evolutionary Biology
• Photosynthesis Research

Background:

• Oxygenic photosynthesis, catalyzed by photosystem II, produces O₂ from water.
• Cyanobacteria are the only prokaryotes performing water oxidation, leading to the assumption it's a late evolutionary innovation.
• The precise origin of water oxidation remains unclear.

Purpose of the Study:

• To investigate the evolutionary timeline of water oxidation.
• To compare the evolutionary rates of photosystem II gene duplication with ancient biological events.
• To determine if water oxidation predates early core gene duplications.

Main Methods:

• Phylogenetic analysis of gene duplication events in photosystem II (CP43/CP47 subunits).
• Comparative analysis of evolutionary rates with ATP synthase, RNA polymerase, and ribosome evolution.
• Ancestral sequence reconstruction and comparative structural biology of photosystem subunits.

Main Results:

• The core photosystem II gene duplication shows evolutionary rate patterns similar to ancient events like ATP synthase duplication and RNA polymerase divergence.
• Evidence suggests water oxidation originated before the ancestral core duplications in photosystem II.
• Evolutionary patterns align with those of fundamental bioenergetic and genetic machinery.

Conclusions:

• Photosynthetic water oxidation likely originated much earlier in life's history than previously assumed.
• The origin of water oxidation is closer to the origin of life and bioenergetics.
• Phylogenetic and phylogenomic species trees alone may underestimate the ancient origins of key biological processes.