Conservation and evolution of the ribosome across the photosynthetic lineage

Regulated biogenesis of photosynthetic proteins by the chloroplast ribosomes is central to plant development and environmental adaptation. Here, we describe changes to the ribosome that occurred during evolution of chloroplasts from cyanobacteria in the photosynthetic lineage based on structural, proteomic and bioinformatic analyses. We identify structural features common to oxygenic photosynthetic organisms and distinct from other bacteria, as well as the gain and loss of ribosomal proteins, rRNA modifications and hibernation factors upon endosymbiosis. We uncover structural variation among land plant lineages at sites that remodel the peptide exit tunnel and features associated with translation initiation. The data challenge the prevailing view of ribosomal features that are specific to the chloroplast by demonstrating that many originated earlier, in cyanobacteria, or later, during land plant evolution.