Plant-exuded choline is used for rhizobial membrane lipid biosynthesis by phosphatidylcholine synthase.
Phosphatidylcholine is a major lipid of eukaryotic membranes, but found in only few prokaryotes. Enzymatic methylation of phosphatidylethanolamine by phospholipid N-methyltransferase was thought to be the only biosynthetic pathway to yield phosphatidylcholine in bacteria. However, mutants of the microsymbiotic soil bacterium Sinorhizobium (Rhizobium) meliloti, defective in phospholipid N-methyltransferase, form phosphatidylcholine in wild type amounts when choline is provided in the growth medium. Here we describe a second bacterial pathway for phosphatidylcholine biosynthesis involving the novel enzymatic activity, phosphatidylcholine synthase, that forms phosphatidylcholine directly from choline and CDP-diacylglycerol in cell-free extracts of S. meliloti. We further demonstrate that roots of host plants of S. meliloti exude choline and that the amounts of exuded choline are sufficient to allow for maximal phosphatidylcholine biosynthesis in S. meliloti via the novel pathway.
Institute of Biotechnology, Technical University of Berlin, Seestrasse 13, D-13353 Berlin, Germany.
K E
KE
de Rudder
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C
Sohlenkamp
O
O
Geiger
D002794:Choline / Q000378:metabolism; D003567:Cytidine Diphosphate Diglycerides / Q000378:metabolism; D003568:Cytidine Monophosphate / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008274:Magnesium; D008345:Manganese; D008563:Membrane Lipids / Q000096:biosynthesis*; D008780:Methyltransferases / Q000378:metabolism*; D017830:Octoxynol; D010713:Phosphatidylcholines / Q000096:biosynthesis*; D050918:Phosphatidylethanolamine N-Methyltransferase; D012231:Rhizobium / Q000201:enzymology*; D013379:Substrate Specificity
D003567:Cytidine Diphosphate Diglycerides; D008563:Membrane Lipids; D010713:Phosphatidylcholines; D008345:Manganese; D017830:Octoxynol; D008780:Methyltransferases; D050918:Phosphatidylethanolamine N-Methyltransferase; D003568:Cytidine Monophosphate; D008274:Magnesium; D002794:Choline