| Further in vivo studies on the role of the molecular chaperone, Hsp93, in plastid protein import. | |
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MedLine Citation:
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PMID: 17376159 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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In Arabidopsis, Hsp93 is encoded by two genes, atHSP93-V and atHSP93-III. We identified two T-DNA mutants for atHSP93-III: one being a partial 'knockdown' (hsp93-III-1) and the other a complete 'knockout' (hsp93-III-2). Homozygotes for both mutants were indistinguishable from wild type. We crossed each mutant to an atHSP93-V knockout, and identified double mutants with strongly chlorotic phenotypes. This implied redundancy, which was confirmed by the complementation of mildly chlorotic hsp93-V plants by atHSP93-III over-expression. While the hsp93-V hsp93-III-1 mutant was doubly homozygous, the second double mutant was heterozygous for hsp93-III-2 (genotype: hsp93-V/hsp93-V; +/hsp93-III-2). Attempts to identify an hsp93-V hsp93-III-2 double homozygote were unsuccessful, indicating that the Hsp93 pool is essential for viability. Consistently, siliques of the second double mutant contained aborted seeds (because of a block in the zygote-embryo transition) and failed ovules (because of a moderate defect in female gametophytes). Double-mutant plants were chlorophyll-deficient, contained under-developed chloroplasts, and exhibited stunted growth. In import assays using a chimeric pre-protein (plastocyanin transit peptide fused to dihydrofolate reductase; PC-DHFR), a clear defect was observed in hsp93-V hsp93-III-1 chloroplasts. Interestingly, while denaturation or stabilization of the DHFR moiety had a strong effect on import efficiency in the wild type, no such effects were observed with double-mutant (or tic40) chloroplasts. This indicated that pre-protein unfolding is not rate-limiting for import into mutant chloroplasts, and suggested that (unlike the situation in mitochondria) the inner membrane import machinery does not contribute to pre-protein unfolding at the organellar surface. |
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Authors:
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Sabina Kovacheva; Jocelyn Bédard; Anthony Wardle; Ramesh Patel; Paul Jarvis |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't Date: 2007-03-21 |
Journal Detail:
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Title: The Plant journal : for cell and molecular biology Volume: 50 ISSN: 0960-7412 ISO Abbreviation: Plant J. Publication Date: 2007 Apr |
Date Detail:
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Created Date: 2007-04-20 Completed Date: 2007-08-13 Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 9207397 Medline TA: Plant J Country: England |
Other Details:
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Languages: eng Pagination: 364-79 Citation Subset: IM |
Affiliation:
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Department of Biology, University of Leicester, Leicester LE1 7RH, UK. |
Export Citation:
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APA/MLA Format Download EndNote Download BibTex |
| MeSH Terms | |
Descriptor/Qualifier:
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Animals Arabidopsis Proteins / genetics, physiology* Chlorophyll / metabolism Chloroplasts / metabolism, ultrastructure Heat-Shock Proteins / genetics, physiology* Immunoblotting Mice Microscopy, Electron, Transmission Molecular Chaperones / genetics, physiology* Mutation Phenotype Plants, Genetically Modified Plastids / metabolism* Protein Transport / genetics, physiology Recombinant Fusion Proteins / genetics, metabolism Reverse Transcriptase Polymerase Chain Reaction Seeds / cytology, genetics, metabolism Tetrahydrofolate Dehydrogenase / genetics, metabolism |
| Chemical | |
Reg. No./Substance:
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0/Arabidopsis Proteins; 0/Heat-Shock Proteins; 0/Molecular Chaperones; 0/Recombinant Fusion Proteins; 1406-65-1/Chlorophyll; EC 1.5.1.3/Tetrahydrofolate Dehydrogenase |
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