Rapid evolutionary divergence of Photosystem I core subunits PsaA and PsaB in the marine prokaryote Prochlorococcus |
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Authors: | Georg WM van der Staay Seung Yeo Moon-van der Staay Laurence Garczarek Frédéric Partensky |
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Institution: | Observatoire Océanologique de Roscoff, CNRS-UPR 9042, Université Pierre et Marie Curie, BP 74, F-29682, Roscoff Cedex, France. |
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Abstract: | The nucleotide sequences of the genes coding for the subunits of the Photosystem I (PS I) core, PsaA and PsaB were determined
for the marine prokaryotic oxyphototrophs Prochlorococcus sp. MED4 (CCMP1378), P. marinus SS120 (CCMP1375) and Synechococcus sp. WH7803. Divergence of these sequences from those of both freshwater cyanobacteria and higher plants was remarkably high,
given the conserved nature of PsaA and PsaB proteins. In particular, the PsaA of marine prokaryotes showed several specific
insertions and deletions with regard to known PsaA sequences. Even in between the two Prochlorococcus strains, which correspond to two genetically different ecotypes with shifted growth irradiance optima, the sequence identity
was only 80.2% for PsaA and 88.9% for PsaB. Possible causes and implications of the fast evolution rates of these two PS I
core subunits are discussed.
This revised version was published online in June 2006 with corrections to the Cover Date. |
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Keywords: | cyanobacteria Photosystem I Synechococcus prochlorophyte Prochlorococcus |
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