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Consequences of Reduction in Concentration of Reaction Centers on the Structure and Function of the Photosynthetic Membrane.

Background

In plant chloroplasts all light-harvesting outer antenna proteins (LHC) are encoded by the nuclear genome, whilst the majority of proteins that form the photosynthetic reaction center complexes (RC) are encoded by the chloroplast genome (1,2). The underlying reasons for this division of the antenna and RC proteins between the genomes remain the subject of much debate (2,3). A carefully orchestrated interaction between the two genomes is required for the response to changes in light quality and quantity because the amounts of RCs and LHCs must be carefully balanced to achieve optimal photosynthetic efficiency and photoprotection. The latter is achieved by formation of non-photochemical energy dissipation in LHCII complexes, NPQ, as well as by the repair of damaged RCII component – D1 protein (4,5).

Aim

The key objective of this PhD project will be to down regulate the expression of D1 protein and other chloroplast-produced proteins of photosystems by chronically treating plants with the chloroplast gene expression inhibitor lincomycin (6) in order to dramatically decrease the amount of RC complexes. This novel method will enable to produce plants (wild type and various antenna mutants) with dramatic increase in LHC/RC ratio (6) and create the membrane almost entirely built of LHC complexes. The consequences of this alteration on the structure and functions of the thylakoid membrane as well as possible practical applications of the isolated “natural light harvesting membrane” will be in focus of this project.

The Ruban laboratory possesses a spectrum of instrumental and biochemical approaches that study the physiology, biochemistry and structure of the whole plant, cell, chloroplast, photosynthetic membrane and individual proteins and pigments. You will receive an extensive training in plant growth in a controlled environment; plant physiology techniques based on chlorophyll fluorescence measurements (PAM) and oxygen evolution; low-temperature and time-resolved fluorescence spectroscopy; analytical and preparatory biochemistry of membrane proteins, pigments and lipids (SDS gel electrophoresis, isoelectric focusing, FPLC, HPLC, westerns); electron microscopy techniques (freeze-fracture (7), thin sections, negative staining), confocal fluorescence microscopy and computational modeling.

Eligibility

In order to qualify for funding from Ciência sem Fronteiras, applicants must be Brazilian nationals and are required to have at least an upper second class degree and a masters degree in a related discipline from a top university anywhere in the world. For more information visit the Ciência sem Fronteiras eligibility pages.

International students must provide evidence of proficient English language skills, see our entry requirements page for further information.

NB If you are interested in self-funding please contact Dr Ruban by e-mail (a.ruban@qmul.ac.uk) to discuss your eligibility for this project.

Application process

Potential candidates should contact Dr Ruban by e-mail (a.ruban@qmul.ac.uk) and submit their CV (including details of two referees) and a cover letter explaining their eligibility and interest in this project.

Applications to Queen Mary and Ciência sem Fronteiras are accepted all year round but we encourage you to contact Dr Ruban as soon as possible.

If you are successful we will give you an offer on the condition that you are given a funding award from Ciência sem Fronteiras. When you have received a conditional offer, apply directly to Ciência sem Fronteiras.

References

  1. Eberhard, S., G. Finazzi, and F. A. Wollman. 2008. The dynamics of photosynthesis. Annu. Rev. Genet. 42:463–515.2.
  2. Ruban, A. (2013) The Photosynthetic Membrane: Molecular Mechanisms and Biophysics of Light Harvesting. Wiley-Blackwell, Chichester, ISBN: 978-1-1199-6053-9.
  3. Allen, J. F., W. B. M. de Paula, ..., J. Nield. 2011. A structural phylogenetic map for chloroplast photosynthesis. Trends Plant Sci. 16: 645–655.
    10.1016/j.tplants.2011.10.004
  4. Ruban, A.V., Johnson, M.P. and Duffy, C.D.P. (2012) Photoprotective molecular switch in photosystem II. Biochim. Biophys. Acta, 1817, 167-181.
    10.1016/j.bbabio.2011.04.007
  5. Ohad, I., D. J. Kyle, and C. J. Arntzen. 1984. Membrane protein damage and repair: removal and replacement of inactivated 32-kilodalton polypeptides in chloroplast membranes. J. Cell Biol. 99:481–485.
  6. Belgio, E., Johnson, M.P., Jurić, S. and Ruban, A.V. (2012) Higher plant photosystem II light harvesting antenna, not the reaction center, determines the excited state lifetime - both the maximum and the non-photochemically quenched. Biophys. J., 102, 2761-2771.
    10.1016/j.bpj.2012.05.004
  7. Johnson, M.P., Goral,T.K., Duffy, C.D.P., Brain, A.P.R., Mullineaux, C.W. and Ruban, A.V. (2011) Photoprotective energy dissipation involves the reorganization of photosystem II light harvesting complexes in the grana membranes of higher plant chloroplasts. Plant Cell, 23, 1468-1479.
    10.1105/tpc.110.081646
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