Translational selection shapes codon usage in the GC-rich genome of Chlamydomonas reinhardtii

In unicellular species codon usage is determined by mutational biases and n atural selection. Among prokaryotes, the influence of these factors is diff erent if the genome is skewed towards AT or GC, since in AT-rich organisms translational selection is absent. On the other hand, in AT-rich unicellula r eukaryotes the two factors are present. In order to understand if GC-rich genomes display a similar behavior, the case of Chlamydomonas reinhardtii was studied. Since we found that translational selection strongly influence s codon usage in this species, we conclude that there is not a common patte rn among unicellular organisms. (C) 2001 Federation of European Biochemical Societies. Published by Elsevier Science B.V. All rights reserved.