Eva Selstam - The Role of Lipids in the Plastid Membrane

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My research deals with the properties of the chloroplast lipids and how they interact with proteins. One major objective is to understand the reason for the formation of the prolamellar body, a cubic membrane structure formed in etioplasts. Another is to elucidate the functions of the different lipids in the photosynthetic membrane.
Eva_selstam_portrait

Prolamellar body membranes in etioplasts of Arabidopsis.

The chloroplast and etioplast membranes differ in protein composition, but have the same characteristic lipid composition, with a large proportion of galactolipids and minor amounts of phospholipids and a sulpholipid. Approximately 50 % of the lipids are monogalactocyl diacylglycerols (MGDG), which form a reversed hexagonal phase with water, while the other lipids form a lamellar phase. This means that the plastid membranes have a lipid composition that is destabilised by high lateral pressure in the hydrophobic region. My interest is to find out if this physical property has an impact on the structure and function of the plastid membranes.
Recently we found that in a lipid mutant of Arabidopsis, where the content of MGDG has increased to over 60% of wild type level, the photosystem I protein complex was unstable. This instability was due to too high a concentrations of MGDG.
The ‘cubic’ prolamellar body membrane is also dependent on the lipid composition since, in a lipid phase diagram a cubic phase is stable between a lamellar and a reversed hexagonal phase. In light, the prolamellar body is transformed to a normal lamellar chloroplast membrane, the thylakoid. In vitro, we have been able to transform the prolamellar body and then reassemble it again. This means that we now can find out what factors are of vital importance for formation of the prolamellar body.

Svensk sammanfattning

Key publications

Williams, W.P., Selstam, E., Brain, T. Bras, W. & Bennett, P. 1998 X-ray diffraction studies of the struactural organisation of prolamellar bodies isolated from Zea mays. FEBS Lett 422:252-254

Selstam E, Schelin J, Brain, T & Williams, WP. 2002. The effects of low pH on the properties of protochlorophyllide oxidoreductase and the organisation of prolamellar bodies of maize (Zea mays). Eur. J. Biochem. 269:2336-2346.

Selstam E, Schelin J Williams, WP and Brain, T. 2007. Structural organisation of prolamellar bodies isolated from Zea mays. Parallel TEM, SAX and absorption spectra measurments on samples subjected to freeze-thaw, reduced pH and high-salt perturburation. Biochim. Biophys. Acta1768:2235-2245.

Ivanov AG, Hendrickson L, Krol M, Selstam E, Oquist G, Hurry V and Huner NPA. 2006 Digalactosyl-diacylglycerol deficiency impairs the capacity for photosyntetic intersys- tem electron transport and state transitionsin Arabidopsis thaliana due to photosystem I acceptor-side limitations. Plant Cell Physiol. 47:1146-1157.

Hendrickson L,Vlcková A, Selstam E, Huner N, Oquist G and Hurry V. 2006. Cold acclimation of the Arabidopsis dgd1 mutant results in recovery from photosystem I-limited photosynthesis. FEBS Lett 580:4959-4968.

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May 2013

Tuesday, May 21, 2013
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