Characterization of photosynthesis in Arabidopsis ER-to-plastid lipid trafficking mutants
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Vascular plants use two pathways to synthesize galactolipids, the predominant lipid species in chloroplasts—a prokaryotic pathway that resides entirely in the chloroplast, and a eukaryotic pathway that involves assembly in the endoplasmic reticulum. Mutants deficient in the endoplasmic reticulum pathway, trigalactosyldiacylglycerol (tgd1-1 and tgd2-1) mutants, had been previously identified with reduced contents of monogalactosyldiacylglycerol and digalactosyldiacylglycerol, and altered lipid molecular species composition. Here, we report that the altered lipid composition affected photosynthesis in lipid trafficking mutants. It was found that proton motive force as measured by electrochromic shift was reduced by ~40 % in both tgd mutants. This effect was accompanied by an increase in thylakoid conductance attributable to ATPase activity and so the rate of ATP synthesis was nearly unchanged. Thylakoid conductance to ions also increased in tgd mutants. However, gross carbon assimilation in tgd mutants as measured by gas exchange was only marginally affected. Rubisco activity, electron transport rate, and photosystem I and II oxidation status were not altered. Despite the large differences in proton motive force, responses to heat and high light stress were similar between tgd mutants and the wild type.
Keywordstgd1-1 tgd2-1 Proton motive force Electrochromic shift Galactolipids Photosynthesis
Non-focusing optics spectrophotometer
Dark-interval relaxation kinetics
Proton motive force
Photosynthetic photon flux density
We thank Dr. David Kramer for his helpful advice on using the NoFOSpec and Dr. Sean E. Weise for his technical assistance with LI-6400. This project was funded by the National Science Foundation Grants IOS-0950574 to T.D.S. and MCB-0741395 to C.B.
- Aronsson H, Schöttler MA, Kelly AA, Sundqvist C, Dörmann P, Karim S, Jarvis P (2008) Monogalactosyldiacylglycerol deficiency in Arabidopsis affects pigment composition in the prolamellar body and impairs thylakoid membrane energization and photoprotection in leaves. Plant Physiol 148:580–592PubMedCrossRefGoogle Scholar
- Ivanov AG, Hendrickson L, Krol M, Selstam E, Oquist G, Hurry V, Huner N (2006) Digalactosyl-diacylglycerol deficiency impairs the capacity for photosynthetic intersystem electron transport and state transitions in Arabidopsis thaliana due to photosystem I acceptor-side limitations. Plant Cell Physiol 47:1146PubMedCrossRefGoogle Scholar
- Sewe KU, Reich R (1977) Effect of molecular polarization on electrochromism of carotenoids. 2. Lutein-chlorophyll complexes—origin of field-indicating absorption-change at 520 nm in membranes of photosynthesis. Zeitschrift Fur Naturforschung 32c:161–171Google Scholar
- Wang Z, Benning C (2011) Arabidopsis thaliana polar glycerolipid profiling by thin layer chromatography (TLC) coupled with gas-liquid chromatography (GLC). J Vis Exp 49:e2518. http://www.jove.com/details.stp?id=2518
- Wellburn AR, Lichtenthaler H (1984) Formulae and program to determine total carotenoids and chlorophylls a and b of leaf extracts in different solvents. Adv Photosynth Res 2:9–12Google Scholar