Paul Jarvis

..Once inside the organelle, many chloroplast proteins engage one of four additional protein sorting mechanisms that direct targeting to the internal thylakoid membrane system...

..These results suggest some role for atToc75-IV during growth in the dark...

..Supporting this notion, yeast two-hybrid and bimolecular fluorescence complementation assays demonstrated the in vivo interaction of Tic40 with Tic110, a protein believed to recruit stromal chaperones to protein import sites...

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..Non-additive interactions amongst the mutations occurred in double mutants, suggesting that the three components may cooperate during chloroplast protein import...

..When both atToc159 and the major isoform of the other subtype, atToc132, were absent, an embryo-lethal phenotype resulted, demonstrating the essential role of Toc159 in the import mechanism...

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..Thus, the ubiquitin-proteasome system acts on plastids to control their development...

..This indicates that the N-terminal region of AtOEP80 is not essential for the targeting, biogenesis, or functionality of the protein, in contrast with atToc75-III, which requires a bipartite targeting sequence...

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..While the Group 2 proteins have been conserved over approximately 1.2 billion (1.2 × 10(9) ) years, they are not essential for normal development...

..These pathways appear to utilize similar TOC complexes equipped with different combinations of homologous GTPase receptors, providing preprotein recognition specificity...

..The data suggest that atToc33 is involved preferentially in the import of photosynthetic proteins and, by extension, that atToc34 is involved in the import of nonphotosynthetic chloroplast proteins...

..Other recent reports have elucidated an intriguing array of protein targeting routes leading to the envelope membranes themselves...

..GUN1 has recently been identified as a chloroplast-localized pentatricopeptide repeat protein that integrates information from several different signalling pathways...

..Furthermore, the D217N and D219N mutations did not affect atToc33 functionality in vivo. The data demonstrate that atToc33 belongs to a novel class of GTPases with unusual nucleotide-binding properties...

..Our results revealed that the converted SPAD values differ from photometric measurements of solvent-extracted chlorophyll by just ~6% on average...

..Compared to protoplastation, this isolation method has significant time and cost savings (approximately 80% and approximately 95%, respectively), and yields chloroplasts with a higher capacity to import proteins...

..Phylogenetic evidence suggests that several translocon subunits are of cyanobacterial origin, indicating that today's import machinery was built around a prokaryotic core...

..Recent studies have provided major new insights into one of these signalling mechanisms, and identified the chlorophyll precursor Mg-protoporphyrin IX as a key signalling molecule...

..These results demonstrate that Toc64/OEP64 is not essential for the efficient import of proteins into chloroplasts in Arabidopsis, and draw into question the functional significance of this component...

..Moreover, the chloroplasts of the sfr2 mutant show clear evidence of rapid damage after a freezing episode, suggesting a role for SFR2 in the protection of the chloroplast...

..Thus, the pH-dependent activation of the violaxanthin de-epoxidase and of the PsbS protein is impaired...

..The mutants complemented ppi1 with equal efficiency in respect of all criteria tested, including protein import efficiency and light stress tolerance. The data suggest that atToc33 phosphorylation may not play an important role in vivo...

..The data demonstrate that atToc33/atToc34 performs a central and essential role during plastid protein import, and indicate that the atToc34 isoform is relatively more important for plastid biogenesis in roots...

..Chloroplasts isolated using the method described here have been successfully used for proteomic analysis, as well as in studies on chloroplast protein import and other aspects of chloroplast biology...