Abstracts now available online - Euro Fed Lipid

Biosynthesis and function of galactolipids
Georg Hölzl, Nicole Gaude, Sandra Witt, Ernst Heinz and Peter Dörmann
Max Planck Institute of Molecular Plant Physiology, Golm, Germany
University of Hamburg, Germany
Chloroplasts are the site of photosynthesis and harbor a unique set of lipids, e.g. the
galactolipids (monogalactosyldiacylglycerol, MGDG; digalactosyldiacylglycerol, DGDG).
MGDG and DGDG are crucial for photosynthetic light reactions. Therefore, DGDG
deficiency caused by mutations in the two DGDG synthases DGD1 and DGD2 result in
reduction in chlorophyll and photosynthetic efficiency. Introduction of a bacterial
glucolipid synthase from Chloroflexus into the dgd1 mutant leads to the accumulation of
a novel lipid, glucosylgalactosyldiacylglycerol (GlcGalDG) in the chloroplasts, and to
complementation of growth and photosynthetic efficiency. Therefore, galactose in the
second position of the DGDG head group can to some extent be functionally replaced
by glucose.
DGDG accumulates in extraplastidial membranes after phosphate deprivation,
but also in the peribacteroid membranes surrounding nitrogen fixing Rhizobia in root
nodules of legumes. Similar to Arabidopsis, the model legume Lotus japonicus contains
two DGDG synthase genes, DGD1 and DGD2. cDNAs were obtained for the two DGDG
synthases, and used to generate transgenic Lotus plants with reduced expression of
DGD1 or DGD2 by RNAi technique. Data will be presented on the nodulation efficiency
of transgenic Lotus plants after inoculation with Sinorhizobium loti.