Requires Mg2+. Diacylglycerol cannot serve as an acceptor molecule for galactosylation as in the reaction catalysed by EC 2.4.1.46, monogalactosyldiacylglyerol synthase. When phosphate is limiting, phospholipids in plant membranes are reduced but these are replaced, at least in part, by the glycolipids digalactosyldiacylglycerol (DGDG) and sulfoquinovosyldiacylglycerol . While both DGD1 and DGD2 are increased under phosphate-limiting conditions, DGD2 does not contribute significantly under optimal growth conditions. DGD2 is responsible for the synthesis of DGDG molecular species that are rich in C16 fatty acids at sn-1 of diacylglycerol whereas DGD1 leads to molecular species rich in C18 fatty acids . The enzyme has been localized to the outer side of chloroplast envelope membranes.
Requires Mg2+. Diacylglycerol cannot serve as an acceptor molecule for galactosylation as in the reaction catalysed by EC 2.4.1.46, monogalactosyldiacylglyerol synthase. When phosphate is limiting, phospholipids in plant membranes are reduced but these are replaced, at least in part, by the glycolipids digalactosyldiacylglycerol (DGDG) and sulfoquinovosyldiacylglycerol [3]. While both DGD1 and DGD2 are increased under phosphate-limiting conditions, DGD2 does not contribute significantly under optimal growth conditions. DGD2 is responsible for the synthesis of DGDG molecular species that are rich in C16 fatty acids at sn-1 of diacylglycerol whereas DGD1 leads to molecular species rich in C18 fatty acids [3]. The enzyme has been localized to the outer side of chloroplast envelope membranes.
DGD1 seems to act preferentially on monogalactosyldiacylglycerol molecular species with 18-carbon fatty acids in the two positions of monogalactosyldiacylglycerol in vivo
DGD2 seems to act preferentially on monogalactosyldiacylglycerol molecular species with 16-carbon fatty acids in the sn-1 position and on 18-carbon fatty acid in the sn-2 position in vivo
disruption of the two digalactosyldiacylglycerol synthase genes DGD1 and DGD2 in Arabidopsis reveals the existence of an additional enzyme of galactolipid synthesis
a null-mutant of Arabidopsis, which lacks the DGDG synthase (DGD1) resulting in a 90% reduction in the amount of DGDG under normal growth conditions, accumulates digalactosyldiacylglycerol after phosphate deprivation up to 60% of the amount present in the wild-type. Extraplastidic biosynthesis of digalactosyldiacylglycerol induced by phosphate deprivation is a biochemical mechanism for plants to conserve phosphate
DGD1 seems to act preferentially on monogalactosyldiacylglycerol molecular species with 18-carbon fatty acids in the two positions of monogalactosyldiacylglycerol in vivo
DGD2 seems to act preferentially on monogalactosyldiacylglycerol molecular species with 16-carbon fatty acids in the sn-1 position and on 18-carbon fatty acid in the sn-2 position in vivo
disruption of the two digalactosyldiacylglycerol synthase genes DGD1 and DGD2 in Arabidopsis reveals the existence of an additional enzyme of galactolipid synthesis
a null-mutant of Arabidopsis, which lacks the DGDG synthase (DGD1) resulting in a 90% reduction in the amount of DGDG under normal growth conditions, accumulates digalactosyldiacylglycerol after phosphate deprivation up to 60% of the amount present in the wild-type. Extraplastidic biosynthesis of digalactosyldiacylglycerol induced by phosphate deprivation is a biochemical mechanism for plants to conserve phosphate
DGD1 associated with the outside of the outer envelope of chloroplasts. Does not require ATP for insertion and is not processed; DGD2 associated with the outside of the outer envelope of chloroplasts. DGD2 is processed and requires ATP for insertion
membrane, outer membrane protein. Insertion of digalactosyldiacylglycerol synthase 1 into the membrane is reduced by either nucleotide depletion or proteolysis of the chloroplasts DGD1 integration
gene 7942dgdA encodiung digalactosyldiacylglycerol synthase is essential. 7942dgdA can be knocked out only when genes for cyanobacterial or plant digalactosyldiacylglycerol synthases are expressed. Lack of digalactosyldiacylglycerol cannot be compensated by the other membrane lipids in Synechococcus elongatus PCC 7942 or by glucosylgalactosyldiacylglycerol synthesized by the beta-GlcT gene of Chloroflexus aurantiacus. Digalactosyldiacylglycerol has an indispensable role and the second galactose molecule is the key
Dgd1 mutants have a greater than 90% reduction in digalactosyldiacylglycerol content, reduced photosynthesis, and altered chloroplast morphology. Mutant plants show an extremely short inflorescence stem. Phloem cap cells are lignified and jasmonic acid-responsive genes are highly upregulated under normal growth conditions. The coronative insensitive1 Dgd1 and allene oxide synthase Dgd1 double mutants no longer exhibit the short inflorescence stem and lignification phenotypes but still have the same lipid profile and reduced photosynthesis as Dgd1 single mutants. Dgd1 mutants display increased levels of jasmonic acid, jasmonic acid-isoleucine, 12-oxo-phytodienoic acid, and arabidopsides. Jasmonic acid biosynthesis in Dgd1 mutants is initially activated through the increased expression of genes encoding 13-lipoxygenases and phospholipase A-Ig3 (At1g51440), and is sustained by further increases in 13-lipoxygenase and allene oxide cyclase mRNA and protein levels
The digalactosyldiacylglycerol (DGDG) synthase DGD1 is inserted into the outer envelope membrane of chloroplasts in a manner independent of the general import pathway and does not depend on direct interaction with monogalactosyldiacylglycerol synthase for DGDG biosynthesis
DGD2, an Arabidopsis gene encoding a UDP-galactose-dependent digalactosyldiacylglycerol synthase is expressed during growth under phosphate-limiting conditions
Disruption of the two digalactosyldiacylglycerol synthase genes DGD1 and DGD2 in Arabidopsis reveals the existence of an additional enzyme of galactolipid synthesis
Reduced bosynthesis of digalactosyldiacylglycerol, a major chloroplast membrane lipid, leads to oxylipin overproduction and phloem cap lignification in Arabidopsis
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2.4.1.241 digalactosyldiacylglycerol synthase
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