Document Detail

Dual targeting of aminoacyl-tRNA synthetases to the mitochondrion and complex plastid in chlorarachniophytes.
MedLine Citation:
PMID:  23038770     Owner:  NLM     Status:  Publisher    
In plants, many nucleus-encoded proteins are targeted to both mitochondria and plastids, and this process is generally mediated by ambiguous N-terminal targeting sequences that are recognized by receptors on both organelles. In many algae, however, plastids were acquired by secondarily engulfing green or red algae, which were retained within the endomembrane system. Protein targeting to these secondary plastids is more complex, and because they do not reside directly in the cytoplasm, dual targeting could not function as it does in plant cells. Here we investigate dual targeting of aminoacyl-tRNA synthetases (aaRSs) in chlorarachniophytes, complex algae that possess secondary plastids and a relict nucleus derived from a green algal endosymbiont. Chlorarachniophytes have four genome-containing compartments, but almost all the aaRSs are nucleus-encoded and present in fewer than four copies (some as few as two), suggesting multiple targeting. We characterized the subcellular localization of two classes, HisRS (three copies) and GlyRS (two copies), using GFP fusion proteins. In both cases, one copy was dually targeted to mitochondria and plastids, but unlike plants this was mediated by translation initiation variants. We also found the periplastidal compartment (the relict green algal cytoplasm) lacks both GlyRS and a cognate tRNA, suggesting pre-charged host tRNAs are imported into this compartment. Leader analysis of other aaRSs suggests alternative translation is a common strategy for dual targeting in these complex cells. Overall, dual targeting to mitochondria and plastids is a shared feature of plastid-bearing organisms, but the increased complexity of trafficking into secondary plastids requires a different strategy.
Yoshihisa Hirakawa; Fabien Burki; Patrick J Keeling
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-10-4
Journal Detail:
Title:  Journal of cell science     Volume:  -     ISSN:  1477-9137     ISO Abbreviation:  J. Cell. Sci.     Publication Date:  2012 Oct 
Date Detail:
Created Date:  2012-10-5     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0052457     Medline TA:  J Cell Sci     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
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