Multiple evolutionary origins of prochlorophytes, the chlorophyll b-containing prokaryotes

Nature. 1992 Jan 16;355(6357):265-7. doi: 10.1038/355265a0.


Prochlorophytes are prokaryotes that carry out oxygenic photosynthesis using chlorophylls a and b, but lack phycobiliproteins as light-harvesting pigments. These characteristics distinguish them from cyanobacteria, which contain phycobiliproteins, but no chlorophyll b. Three prochlorophyte genera have been described: Prochloron, Prochlorothrix and Prochlorococcus. The prochlorophytes share their pigment characteristics with green plant and euglenoid chloroplasts, which has led to a debate on whether these chloroplasts may have arisen from an endosymbiotic prochlorophyte rather than a cyanobacterium. Molecular sequence data, including those presented here based on a fragment of the rpoC1 gene encoding a subunit of DNA-dependent RNA polymerase, indicate that the known prochlorophyte lineages do not include the direct ancestor of chloroplasts. We also show that the prochlorophytes are a highly diverged polyphyletic group. Thus the use of chlorophyll b as a light-harvesting pigment has developed independently several times in evolution. Similar conclusions have been reached in parallel studies using 16S ribosomal RNA sequences.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Anabaena / genetics
  • Biological Evolution*
  • Chlorophyll / metabolism*
  • Cloning, Molecular
  • Cyanobacteria / enzymology
  • Cyanobacteria / genetics*
  • DNA-Directed RNA Polymerases / genetics*
  • Molecular Sequence Data
  • Photosynthesis
  • Phylogeny
  • Plants / enzymology
  • Plants / genetics
  • Polymerase Chain Reaction
  • Sequence Homology, Nucleic Acid


  • Chlorophyll
  • chlorophyll b
  • DNA-Directed RNA Polymerases

Associated data

  • GENBANK/Z11152
  • GENBANK/Z11153
  • GENBANK/Z11154
  • GENBANK/Z11155
  • GENBANK/Z11159
  • GENBANK/Z11160
  • GENBANK/Z11161