CHLOROPLAST RIBOSOME ASSOCIATED supports translation under stress and interacts with the ribosomal 30S subunit
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- CHLOROPLAST RIBOSOME ASSOCIATED Supports Translation under Stress and Interacts with the Ribosomal 30S Subunit
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Chloroplast ribosomes, which originated from cyanobacteria, comprise a large (50S) and small (30S) subunit containing ribosomal RNAs (rRNAs) and various ribosomal proteins. Genes for many chloroplast ribosomal proteins, as well as proteins with auxiliary roles in ribosome biogenesis or functioning, reside in the nucleus. Here, we identified Arabidopsis thaliana CHLOROPLAST RIBOSOME ASSOCIATED (CRASS), a member of the latter class of proteins, based on the tight co-expression of its mRNA with transcripts for nucleus-encoded chloroplast ribosomal proteins. CRASS was acquired during the evolution of embryophytes and is localized to the chloroplast stroma. Loss of CRASS results in minor defects in development, photosynthetic efficiency, and chloroplast translation activity under controlled growth conditions, but these phenotypes are greatly exacerbated under stress conditions induced by the translational inhibitors lincomycin or chloramphenicol or by cold treatment. The CRASS protein comigrates with chloroplast ribosomal particles and co-immunoprecipitates with the 16S rRNA and several chloroplast ribosomal proteins, particularly the plastid ribosomal protein of the 30S subunit (PRPS)1 and PRPS5. The association of CRASS with PRPS1 and PRPS5 is independent of rRNA and is not detectable in yeast two-hybrid experiments, implying that either CRASS interacts indirectly with PRPS1 and PRPS5 via another component of the small ribosomal subunit or that it recognizes structural features of the multi-protein/rRNA particle. CRASS plays a role in the biogenesis and/or stability of the chloroplast ribosome that becomes critical under certain stressful conditions when ribosomal activity is compromised.
|Status||Udgivet - 2018|
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