Chloroplasts belong to a diverse family of plant organelles termed plastids . Chloroplasts are responsible for photosynthesis and many essential biosynthetic functions. As photosynthesis is the only significant mechanism of energy-input into the biosphere, chloroplasts are extremely important, not just to plants but to animals and mankind alike. Development of chloroplasts (and other plastids) depends on the import of thousands of nucleus-encoded proteins from the cytosol. Such protein import is mediated by multiprotein complexes in the plastid envelope membranes termed TOC and TIC (for Translocon at the Outer/Inner envelope membrane of Chloroplasts) [1,2].
The outer membrane of chloroplasts (like those of bacteria and mitochondria) contains β-barrel channel proteins. One of these proteins, Toc75, forms the main translocation pore of the TOC complex [2,3]. Recent work in bacteria and mitochondria identified Omp85-type proteins (BamA in bacteria; Sam50 in mitochondria) as important mediators of the assembly of β-barrel proteins. However, little is known about the corresponding mechanisms in chloroplasts: an Omp85-type protein called OEP80 is proposed to be involved, but there is presently only limited evidence to support this hypothesis . To address this hypothesis in an in vivo context, Arabidopsis plants that are OEP80-deficient will be characterized in detail. The aim will be to elucidate the role of the OEP80 protein, and to investigate the mechanisms underlying the assembly of Toc75 and other β-barrels in chloroplasts.
1. Jarvis, P. and López-Juez, E. (2013) Biogenesis and homeostasis of chloroplasts and other plastids. Nat. Rev. Mol. Cell Biol. 14:787-802.
2. Jarvis, P. (2008) Targeting of nucleus-encoded proteins to chloroplasts in plants (Tansley Review). New Phytol. 179:257-285.
3. Baldwin, A., Wardle, A., Patel, R., Dudley, P., Park, S.K., Twell, D., Inoue, K. and Jarvis, P. (2005) A molecular-genetic study of the Arabidopsis Toc75 gene family. Plant Physiol. 138: 715-733.
4. Huang, W. et al. (2011) In vivo analyses of the roles of essential Omp85-related proteins in the chloroplast outer envelope membrane. Plant Physiol. 157: 147-159.
This project would suit candidates with a strong background in one or more of the following areas: biological sciences, molecular biology, cell biology, biochemistry, genetics.
Ling, Q. and Jarvis, P. (2015) Regulation of chloroplast protein import by the ubiquitin E3 ligase SP1 is important for stress tolerance in plants. Curr. Biol. 25:2527-2534.
Ling, Q., Huang, W., Baldwin, A. and Jarvis, P. (2012) Chloroplast biogenesis is regulated by direct action of the ubiquitin-proteasome system. Science 338: 655-659.
Jarvis, P. and López-Juez, E. (2013) Biogenesis and homeostasis of chloroplasts and other plastids. Nat. Rev. Mol. Cell Biol. 14: 787-802.
Huang, W. et al. (2011) In vivo analyses of the roles of essential Omp85-related proteins in the chloroplast outer envelope membrane. Plant Physiol. 157: 147-159.
Jarvis, P. (2008) Targeting of nucleus-encoded proteins to chloroplasts in plants (Tansley Review). New Phytol. 179: 257-285.