Profiling Membrane Lipids in Plant Stress Responses

Abstract

A sensitive approach based on electrospray ionization tandem mass spectrometry has been employed to profile membrane lipid molecular species in Arabidopsis undergoing cold and freezing stresses. Freezing at a sublethal temperature induced a decline in many molecular species of phosphatidylcholine (PC), phosphatidylethanolamine (PE), and phosphatidylglycerol (PG) but induced an increase in phosphatidic acid (PA) and lysophospholipids. To probe the metabolic steps generating these changes, lipids of Arabidopsis deficient in the most abundant phospholipase D, PLD␣, were analyzed. The PC content dropped only half as much, and PA levels rose only half as high in the PLD␣-deficient plants as in wild-type plants. In contrast, neither PE nor PG levels decreased significantly more in wild-type plants than in PLD␣-deficient plants. These data suggest that PC, rather than PE and PG, is the major in vivo substrate of PLD␣. The action of PLD␣ during freezing is of special interest because Arabidopsis plants that are deficient in PLD␣ have improved tolerance to freezing. The greater loss of PC and increase in PA in wild-type plants as compared with PLD␣-deficient plants may be responsible for destabilizing membrane bilayer structure, resulting in a greater propensity toward membrane fusion and cell death in wild-type plants.Eukaryotic membranes contain diverse lipid molecular species, and the lipid composition changes in response to both internal and external cues. Knowing how lipid molecular species change and how the changes are generated is important to the understanding of membrane and cell functions. Detailed study of membrane lipid changes, however, has been technically challenging because of the complexity of lipid molecular species and analytical procedures. Recently, an approach based on electrospray ionization tandem mass spectrometry (ESI-MS/ MS) 1 has been developed to comprehensively analyze lipid composition in animal and yeast cells (1-9). It requires only simple sample preparation and small samples to identify and quantify lipid molecular species. Expansion of this approach to plants, which harbor unique lipids, such as galactosylglycerolipids, should greatly facilitate the understanding of lipid functions in plant growth, development, and stress responses.Plant stress caused by freezing has been an area of intensive research for many years, but the molecular and cellular mechanisms of freezing injury and tolerance are not well understood (10 -12). The best documented freezing injury occurs at the membrane level. One major form of freezing damage is due to the formation of lipid hexagonal II phase in regions where the plasma membrane and the chloroplast envelope are closely apposed (13,14). Changes in membrane lipid composition occur when plants are exposed to freezing temperatures (15). Lipid hydrolysis has been proposed to be mainly responsible for the change, but the role of lipid hydrolysis in freezing injury and tolerance is not clear.In plants, several lipolytic enzymatic activities have been described, ...

Lipid and oxylipin profiles during aging and sprout development in potato tubers (Solanum tuberosum L.)

“…Phospholipid and galactolipid analyses were performed by electrospray ionisation tandem mass spectrometry (ESI-MS/MS) using internal standards as described in [25], except that, for phospholipid analysis, 150 Al of extract were used, and for galactolipid analysis, 225 Al of extract were used. The extraction and analysis were performed on five independent samples of potato tubers at each time point.…”

“…Lipid profiling by ESI-MS/MS requires only simple sample preparation and small amounts of plant material. This technique has been used previously to profile membrane lipids in a plant stress response [25], and here it is utilized in a new application. Analysis of lipid extracts by ESI-MS/MS allowed the identification and quantification of the principal phospholipids and galactolipids during the storage of potato tubers.…”

Lipidomic Analysis of Toxoplasma gondii Reveals Unusual Polar Lipids

“…An automated electrospray ionization-tandem mass spectrometry approach was used and data acquisition and analysis and acyl group identification were carried out as described previously (16,17) with some modifications. An aliquot of extract (0.040 ml) was taken for mass spectrometry analysis.…”

Profiling and tandem mass spectrometry analysis of aminoacylated phospholipids in Bacillus subtilis

“…The loss of a neutral head group from positive (protonated or sodiated) molecular ions of phospholipids produced dehydroxyl-diacylglycerol cations ([DAG-OH] + ) as the most abundant fragments. This neutral loss feature is commonly used to search for phospholipids with certain head groups 34 . For instance, PE can be identified by a scan for the neutral loss of phosphoethanolamine (141 amu).…”

“…The amide-linked PE derivative cannot be identified by their PG counterparts’ dissociation into deprotonated aminoacyl ions. We therefore employed the neutral loss (NL) scanning methodology based on those commonly used for identifying phosphatidylethanolamine (NL of 141 amu head group), phosphatidylserine (NL of 185 amu head group), phosphatitylacid (NL of 115 amu ammoniated head group) and phosphatidylinositol (NL of 277 amu ammoniated head group) 34 . We also searched for precursors of the most abundant dehydroxyl-diacylglycerol cation (523 amu) which has the dominant fatty acyl composition of (30:0).…”