Photosystem I gene cassettes are present in marine virus genomes

Nature. 2009 Sep 10;461(7261):258-262. doi: 10.1038/nature08284. Epub 2009 Aug 26.


Cyanobacteria of the Synechococcus and Prochlorococcus genera are important contributors to photosynthetic productivity in the open oceans. Recently, core photosystem II (PSII) genes were identified in cyanophages and proposed to function in photosynthesis and in increasing viral fitness by supplementing the host production of these proteins. Here we show evidence for the presence of photosystem I (PSI) genes in the genomes of viruses that infect these marine cyanobacteria, using pre-existing metagenomic data from the global ocean sampling expedition as well as from viral biomes. The seven cyanobacterial core PSI genes identified in this study, psaA, B, C, D, E, K and a unique J and F fusion, form a cluster in cyanophage genomes, suggestive of selection for a distinct function in the virus life cycle. The existence of this PSI cluster was confirmed with overlapping and long polymerase chain reaction on environmental DNA from the Northern Line Islands. Potentially, the seven proteins encoded by the viral genes are sufficient to form an intact monomeric PSI complex. Projection of viral predicted peptides on the cyanobacterial PSI crystal structure suggested that the viral-PSI components might provide a unique way of funnelling reducing power from respiratory and other electron transfer chains to the PSI.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adhesins, Bacterial / chemistry
  • Adhesins, Bacterial / genetics
  • Amino Acid Sequence
  • Bacteriophages / genetics*
  • Bacteriophages / metabolism
  • Biodiversity
  • Genes, Bacterial / genetics
  • Genes, Viral / genetics*
  • Genome, Bacterial / genetics
  • Genome, Viral / genetics*
  • Geography
  • Lipoproteins / chemistry
  • Lipoproteins / genetics
  • Models, Molecular
  • Molecular Sequence Data
  • Oceans and Seas
  • Open Reading Frames / genetics
  • Oxidation-Reduction
  • Photosynthesis / genetics
  • Photosystem I Protein Complex / chemistry
  • Photosystem I Protein Complex / genetics*
  • Phylogeny
  • Polymerase Chain Reaction
  • Prochlorococcus / virology*
  • Protein Conformation
  • Seawater / microbiology*
  • Synechococcus / virology*
  • Viral Proteins / chemistry
  • Viral Proteins / genetics
  • Viral Proteins / metabolism
  • Water Microbiology


  • Adhesins, Bacterial
  • Lipoproteins
  • Photosystem I Protein Complex
  • PsaA protein, Streptococcus
  • Viral Proteins

Associated data

  • GENBANK/EU926752
  • GENBANK/EU926753
  • GENBANK/EU926754
  • GENBANK/EU926755
  • GENBANK/EU926756
  • GENBANK/EU926757
  • GENBANK/EU926758
  • GENBANK/EU926759
  • GENBANK/EU926760
  • GENBANK/EU926761
  • GENBANK/GQ268816