Digalactosyl-diacylglycerol-deficiency lowers the thermal stability of thylakoid membranes

S.K.B. Krumova, S. Laptenok, L. Kovács, T. Toth, A. van Hoek, G. Garab, H. van Amerongen

Research output: Contribution to journalArticleAcademicpeer-review

39 Citations (Scopus)

Abstract

We investigated the effects of digalactosyl-diacylglycerol (DGDG) on the organization and thermal stability of thylakoid membranes, using wild-type Arabidopsis thaliana and the DGDG-deficient mutant, dgd1. Circular-dichroism measurements reveal that DGDG-deficiency hampers the formation of the chirally organized macrodomains containing the main chlorophyll a/b light-harvesting complexes. The mutation also brings about changes in the overall chlorophyll fluorescence lifetimes, measured in whole leaves as well as in isolated thylakoids. As shown by time-resolved measurements, using the lipophylic fluorescence probe Merocyanine 540 (MC540), the altered lipid composition affects the packing of lipids in the thylakoid membranes but, as revealed by flash-induced electrochromic absorbance changes, the membranes retain their ability for energization. Thermal stability measurements revealed more significant differences. The disassembly of the chiral macrodomains around 55°C, the thermal destabilization of photosystem I complex at 61°C as detected by green gel electrophoresis, as well as the sharp drop in the overall chlorophyll fluorescence lifetime above 45°C (values for the wild type—WT) occur at 4–7°C lower temperatures in dgd1. Similar differences are revealed in the temperature dependence of the lipid packing and the membrane permeability: at elevated temperatures MC540 appears to be extruded from the dgd1 membrane bilayer around 35°C, whereas in WT, it remains lipid-bound up to 45°C and dgd1 and WT membranes become leaky around 35 and 45°C, respectively. It is concluded that DGDG plays important roles in the overall organization of thylakoid membranes especially at elevated temperatures.
Original languageEnglish
Pages (from-to)229-242
JournalPhotosynthesis Research
Volume105
Issue number3
DOIs
Publication statusPublished - 2010

Keywords

  • light-harvesting-complex
  • excitation-energy transfer
  • charge separation kinetics
  • pigment-protein complexes
  • intact photosystem-i
  • arabidopsis-thaliana
  • circular-dichroism
  • dgd1 mutant
  • higher-plants
  • chlorophyll fluorescence

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