| Abstract Detail
Lipids Bates, Philip [1], Ohlrogge, John [2], Pollard, Mike [2]. The biosynthesis of phosphatidylcholine in pea leaves involves acyl-editing with newly synthesized and recycled acyl-chains. In pea leaves 95% of fatty acids (FA) synthesized in the plastid are exported for assembly of eukaryotic glycerolipids. It is often assumed that the major products of plastid FA synthesis (18:1 and 16:0) are first incorporated into 18:1/18:1 and 16:0/18:1 molecular species of eukaryotic phosphatidic acid (PA). PA is then converted to phosphatidylcholine (PC), the major eukaryotic phospholipid and major site of acyl desaturation, to produce PC molecular species dominated by 18:2, 18:3 and 16:0 acyl-chains. However, using in vivo [14C]acetate and [14C]glycerol pea leaf labeling and [14C]CO2 labeling of pea seedlings we demonstrate that acyl-editing is involved in the initial steps of eukaryotic glycerolipid synthesis. We could not detect a precursor-product relationship between PA and PC when tracking the nascent synthesized FA labeled from [14C]acetate at very early time points (30 sec). Furthermore, molecular species analysis of short time point [14C]acetate and [14C]CO2 labeled PC demonstrates that >90% of [14C]18:1 and [14C]16:0 acyl-chains esterified to PC are present as molecular species containing one labeled and one unlabeled acyl-chain (18:2, 18:3 or 16:0). [14C]Glycerol labeling at early time points revealed a different set of PC molecular species highly enriched with 18:2, 18:3 and 16:0 FA, but not 18:1. Thus we conclude that newly synthesized acyl-chains are not initially incorporated into the assumed PA molecular species. Instead, we propose that most nascent FA are esterified directly into PC through an acyl-editing mechanism. The acyl-chains removed from PC to allow for acyl-editing can be used for the net synthesis of eukaryotic glycerolipids through glycerol-3-phosphate acylation.
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1 - Michigan State University, Biochemistry and Molecular Biology, 362 Plant Biology Building, East Lansing, MI, 48824, USA
2 - Michigan State University, Plant Biology
Keywords:
Phosphatidylcholine
acyl editing
lipid remodeling
Lipids
eukaryotic lipids
lipid trafficing
phosphatidic acid
metabolic flux.
Presentation Type: Plant Biology Abstract
Session: P
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM
Number: P21003
Abstract ID:253 |
