Photosynthetic energy conversion under extreme conditions—II: The significance of lipids under light limited growth in Antarctic sea ice diatoms

Mock, Thomas ORCID: https://orcid.org/0000-0001-9604-0362 and Kroon, Bernd M. A. (2002) Photosynthetic energy conversion under extreme conditions—II: The significance of lipids under light limited growth in Antarctic sea ice diatoms. Phytochemistry, 61 (1). pp. 53-60. ISSN 1873-3700

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Abstract

Low photosynthetic active radiation is a strong determinant in the development and growth of sea ice algae. The algae appear to have universal mechanisms to overcome light limitation. One important process, which is induced under light limitation, is the desaturation of chloroplast membrane lipids. In order to discover whether this process is universally valid in sea ice diatoms, we investigated three species coexisting in chemostats illuminated with 15 and 2 µmol photons m-2 s-1 at -1 °C. Growth under 2 µmol photons m-2 s-1 caused a 50% increase in monogalactosyldiacylglycerols (MGDG) thylakoid membrane related 20:5 n-3 fatty acids. This fatty acid supports the fluidity of the thylakoid membrane and therefore the velocity of electron flow, which is indicated by increasing rate constants for the electron transport between QA (first stable electron acceptor) and bound QB (second stable electron acceptor) (11.16±1.34 to 23.24±1.35 relative units). Two µmol photons m-2 s-1 furthermore resulted in higher amounts of non-lipid bilayer forming MGDG in relation to other bilayer forming lipids, especially digalactosydiacylglycerol (DGDG). The ratio of MGDG:DGDG increased from 3.4±0.3 to 5.7±0.3. The existence of bilayer thylakoid membranes with high proportions of non. bilayer forming lipids is only possible when sufficient thylakoid pigment-protein complexes are present. If more thylakoid pigment-protein complexes are present in membranes, as found under extreme light limitation, less bilayer forming lipids such as DGDG are required to stabilize the bilayer structure. Differences in protein contents between both light intensities were not found. Consequently pigment contents which nearly doubled under 2 µmol photons m-2 s-1 must be responsible in balancing the potential stability loss resulting from an increase in MGDG:DGDG ratio.

Item Type:	Article
Faculty \ School:	Faculty of Science > School of Environmental Sciences University of East Anglia Research Groups/Centres > Theme - ClimateUEA
UEA Research Groups:	Faculty of Science > Research Centres > Centre for Ecology, Evolution and Conservation Faculty of Science > Research Groups > Environmental Biology Faculty of Science > Research Groups > Centre for Ocean and Atmospheric Sciences
Depositing User:	Rosie Cullington
Date Deposited:	01 Jul 2011 08:44
Last Modified:	13 Apr 2023 13:40
URI:	https://ueaeprints.uea.ac.uk/id/eprint/33142
DOI:	10.1016/S0031-9422(02)00215-7

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