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Efficient translation in chloroplasts requires element(s) upstream of the putative ribosome binding site from atpI
Author(s) -
Baecker Joshua J.,
Sneddon John C.,
Hollingsworth Margaret J.
Publication year - 2009
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.3732/ajb.0800259
Subject(s) - biology , chloroplast , translation (biology) , gene , ribosomal binding site , genetics , untranslated region , eukaryotic translation , five prime untranslated region , ribosome , translational efficiency , genome , reporter gene , gene expression , computational biology , rna , messenger rna
Thousands of proteins make up a chloroplast, but fewer than 100 are encoded by the chloroplast genome. Despite this low number, expression of chloroplast‐encoded genes is essential for plant survival. Every chloroplast has its own gene expression system with a major regulatory point at the initiation of protein synthesis (translation). In chloroplasts, most protein‐encoding genes contain elements resembling the ribosome binding sites (RBS) found in prokaryotes. In vitro, these putative chloroplast ribosome binding sequences vary in their ability to support translation. Here we report results from an investigation into effects of the predicted RBS for the tobacco chloroplast atpI gene on translation in vivo. Two reporter constructs, differing only in their 5′‐untranslated regions (5′UTRs) were stably incorporated into tobacco chloroplast genomes and their expression analyzed. One 5′UTR was derived from the wild‐type (WT) atpI gene. The second, Holo‐substitution (Holo‐sub), had nonchloroplast sequence replacing all wild‐type nucleotides, except for the putative RBS. The abundance of reporter RNA was the same for both 5′UTRs. However, translation controlled by Holo‐sub was less than 4% that controlled by WT. These in vivo experiments support the idea that translation initiation in land plant chloroplasts depends on 5′UTR elements outside the putative RBS.