Membrane phospholipids as a phosphate reserve: the dynamic nature of phospholipid-to-digalactosyl diacylglycerol exchange in higher plants.
It is well established that phosphate deficiency induces the replacement of membrane phospholipid with non-phosphorous lipids in extra-plastidial membranes (e.g. plasma membrane, tonoplast, mitochondria). The predominant replacement lipid is digalactosyl diacylglycerol (DGDG). This paper reports that the phospholipid-to-DGDG replacement is reversible, and that when oat seedlings are re-supplied with radio-labelled phosphate, it is initially recovered primarily in phosphatidylcholine (PC). Within 2 d, the shoot contains more than half of the lipid-associated radiolabel, reflecting phosphate translocation. Oat was also cultivated in different concentrations of phosphate and the DGDG/PC ratio in roots and phospholipase activities in isolated plasma membranes was assayed after different times of cultivation. The DGDG/PC ratio in root tissue correlated more closely with plasma membrane-localized phospholipase D, yielding phosphatidic acid (PA), than with plasma membrane-localized PA phosphatase, the activity that results in a decreased proportion of phospolipids. The lipid degradation data did not reflect a significant involvement of phospholipase C, although a putative phospholipase C analogue, non-specific phospholipase C4 (NPC4), was present in oat roots. The correlation between increased phospholipase D activity and DGDG/PC ratio is consistent with a model where phospholipid-to-DGDG replacement involves formation of PA that readily is removed from the plasma membrane for further degradation elsewhere.
Tjellström
Henrik
H
Department of Plant and Environmental Sciences, University of Gothenburg, Goteborg, Sweden.
Andersson
Mats X
MX
Larsson
Karin E
KE
Sandelius
Anna Stina
AS
D018554:Avena / Q000737:chemistry / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism*; D005308:Fertilizers; D038983:Galactolipids / Q000378:metabolism*; D010710:Phosphates / Q000378:metabolism*; D010712:Phosphatidic Acids / Q000378:metabolism*; D010713:Phosphatidylcholines / Q000378:metabolism; D010740:Phospholipases / Q000378:metabolism; D013431:Sulfates / Q000378:metabolism
D005308:Fertilizers; D038983:Galactolipids; D010710:Phosphates; D010712:Phosphatidic Acids; D010713:Phosphatidylcholines; D013431:Sulfates; C007388:digalactosyldiacylglycerol; D010740:Phospholipases