The Arabidopsis Protein CONSERVED ONLY IN THE GREEN LINEAGE20 is Required for Plastid 50S Ribosome Biogenesis

Biogenesis of plastid ribosomes is assisted by auxiliary factors which process and modify ribosomal RNAs (rRNA) or are involved in ribosome assembly. In comparison to bacterial and mitochondrial ribosomes, plastid ribosome biogenesis is less well understood and only few auxiliary factors have been described, so far. In this study, we report the functional characterization of CGL20 (CONSERVED ONLY IN THE GREEN LINEAGE20) in Arabidopsis thaliana (AtCGL20), a small proline-rich protein targeted to mitochondria and chloroplasts. Its absence is accompanied with a general reduction in chloroplast protein content that leads to a virescent growth phenotype.