The plastid outer envelope – a highly dynamic interface between plastid and cytoplasm
Open Access
- 1 January 2011
- journal article
- Published by Frontiers Media SA in Frontiers in Plant Science
- Vol. 2, 97
- https://doi.org/10.3389/fpls.2011.00097
Abstract
Plastids are the defining organelles of all photosynthetic eukaryotes. They are the site of photosynthesis and of a large number of other essential metabolic pathways, such as fatty acid and amino acid biosyntheses, sulfur and nitrogen assimilation, and aromatic and terpenoid compound production, to mention only a few examples. The metabolism of plastids is heavily intertwined and connected with that of the surrounding cytosol, thus causing massive traffic of metabolic precursors, intermediates, and products. Two layers of biological membranes that are called the inner (IE) and the outer (OE) plastid envelope membranes bound the plastids of Archaeplastida. While the IE is generally accepted as the osmo-regulatory barrier between cytosol and stroma, the OE was considered to represent an unspecific molecular sieve, permeable for molecules of up to 10 kDa. However, after the discovery of small substrate specific pores in the OE, this view has come under scrutiny. In addition to controlling metabolic fluxes between plastid and cytosol, the OE is also crucial for protein import into the chloroplast. It contains the receptors and translocation channel of the TOC complex that is required for the canonical post-translational import of nuclear-encoded, plastid-targeted proteins. Further, the OE is a metabolically active compartment of the chloroplast, being involved in, e.g., fatty acid metabolism and membrane lipid production. Also, recent findings hint on the OE as a defense platform against several biotic and abiotic stress conditions, such as cold acclimation, freezing tolerance, and phosphate deprivation. Moreover, dynamic non-covalent interactions between the OE and the endomembrane system are thought to play important roles in lipid and non-canonical protein trafficking between plastid and endoplasmic reticulum. While proteomics and bioinformatics has provided us with comprehensive but still incomplete information on proteins localized in the plastid IE, the stroma, and the thylakoids, our knowledge of the protein composition of the plastid OE is far from complete. In this article, we report on the recent progress in discovering novel OE proteins to draw a conclusive picture of the OE. A “parts list” of the plastid OE will be presented, using data generated by proteomics of plastids isolated from various plant sources.Keywords
This publication has 103 references indexed in Scilit:
- Inventory and Comparative Analysis of Rice and Arabidopsis ATP-binding Cassette (ABC) SystemsJournal of Molecular Biology, 2004
- Import Pathways of Chloroplast Interior Proteins and the Outer-Membrane Protein OEP14 Converge at Toc75Plant Cell, 2004
- The Roles of Toc34 and Toc75 in Targeting the Toc159 Preprotein Receptor to ChloroplastsJournal of Biological Chemistry, 2003
- Cell cycle-dependent modulation of FtsZ expression in synchronized tobacco BY2 cellsMolecular Genetics and Genomics, 2002
- Hydroperoxide lyase depletion in transgenic potato plants leads to an increase in aphid performanceProceedings of the National Academy of Sciences of the United States of America, 2001
- Insertion of OEP14 into the Outer Envelope Membrane Is Mediated by Proteinaceous Components of ChloroplastsPlant Cell, 2000
- The preprotein translocase of the mitochondrial inner membrane: function and evolutionJournal of Molecular Biology, 1999
- A High-Conductance Solute Channel in the Chloroplastic Outer Envelope from PeaPlant Cell, 1998
- Targeting of proteins to the outer envelope membrane uses a different pathway than transport into chloroplasts.Plant Cell, 1991
- The enzymology of lysine biosynthesis in higher plantsFEBS Letters, 1980