MBE Advance Access first published online on August 4, 2008
This version published online on August 22, 2008
Molecular Biology and Evolution, doi:10.1093/molbev/msn168
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Research Article |
Clues about the genetic basis of adaptation emerge from comparing the proteomes of two Ostreococcus ecotypes (Chlorophyta, Prasinophyceae)
1 UPMC Univ Paris 06, UMR 7628, MBCE, Observatoire Océanologique, F-66651, Banyuls/mer, France
2 CNRS, UMR 7628, MBCE, Observatoire Océanologique, F-66651, Banyuls/mer, France
3 Université de Perpignan Via Domitia, Laboratoire de Mathématiques, Physiques et Systèmes (EA 4217), 52 Avenue Paul Alduy, 66 860 Perpignan Cedex, France
* corresponding author: gwenael.piganeau{at}obs-banyuls.fr, Fax: 00 33 4 68 88 73 98, Tel: 00 33 4 68 88 73 43
Received for publication March 12, 2008. Revision received June 16, 2008. Accepted for publication July 21, 2008.
We compared the proteomes of two picoplanktonic Ostreococcus unicellular green algal ecotypes to analyse the genetic basis of their adaptation to their ecological niches. We first investigated the function of the species-specific genes using gene ontology databases and similarity searches. Although most species-specific genes had no known function, we identified several species-specific functions involved in various cellular processes, which could be critical for environmental adaptations. Additionally, we investigated the rate of evolution of orthologous genes, and its distribution across chromosomes. We show that faster evolving genes encode significantly more membrane or excreted proteins, consistent with the notion that selection acts on cell surface modifications that is driven by selection for resistance to viruses and grazers, keystone actors of phytoplankton evolution. The relationship between GC content and chromosome length also suggests that both strains have experienced recombination since their divergence, and that lack of recombination on the two outlier chromosomes could explain part of their peculiar genomic features, including higher rates of evolution.
Key Words: picoeukaryotes genome comparison GC content selection adaptation
The corrected version of this article is now available.