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Updated: Jul 28, 2026
10:18
Analysis of Protein Import into Chloroplasts Isolated from Stressed Plants
Published on: November 1, 2016
A role for initiation codon context in chloroplast translation.
D Esposito1, A J Hicks, D B Stern
1Department of Molecular Biology and Genetics and Boyce Thompson Institute for Plant Research, Cornell University, Tower Road, Ithaca, New York 14853, USA.
The Plant Cell
|October 12, 2001
Summary
Chloroplast protein synthesis relies on initiation codon context. Mutations disrupting fMet-tRNA base pairing impaired translation, suggesting this interaction is vital for chloroplast gene expression.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Chloroplast protein synthesis utilizes specific initiation codon contexts.
- Prokaryotic initiation involves potential base pairing with 16S rRNA or fMet-tRNA.
Purpose of the Study:
- To investigate the role of the -1 triplet (nucleotides upstream of the initiation codon) in chloroplast translation.
- To determine the in vivo relevance of proposed base pairing interactions in Chlamydomonas reinhardtii.
Main Methods:
- Site-directed mutagenesis of the -1 triplet in two chloroplast genes.
- Assessing mRNA stability and translation efficiency in vivo.
- Analyzing the impact of mutations on protein synthesis under varying temperatures.
Main Results:
- Chloroplast mRNA stability was unaffected by mutations.
- Specific -1 triplet mutations caused temperature-sensitive translation decreases, especially with an AUU initiation codon.
- Disruption of proposed fMet-tRNA anticodon loop base pairing negatively impacted translation.
Conclusions:
- The extended base pairing interaction with fMet-tRNA anticodon loop appears crucial for in vivo chloroplast translation.
- Base pairing with the 530 loop of 16S rRNA is unlikely to occur in vivo.
- Initiation codon context may compensate for the absence of Shine-Dalgarno sequences in chloroplast mRNAs.
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