Presence Of Lipid Transfer Protein Research Articles

Role of Pea LTPs and Abscisic Acid in Salt-Stressed Roots.

Lipid transfer proteins (LTPs) are a class of small, cationic proteins that bind and transfer lipids and play an important role in plant defense. However, their precise biological role in plants under adverse conditions including salinity and possible regulation by stress hormone abscisic acid (ABA) remains unknown. In this work, we studied the localization of LTPs and ABA in the roots of pea plants using specific antibodies. Presence of LTPs was detected on the periphery of the cells mainly located in the phloem. Mild salt stress (50 mM NaCI) led to slowing plant growth and higher immunostaining for LTPs in the phloem. The deposition of suberin in Casparian bands located in the endoderma revealed with Sudan III was shown to be more intensive under salt stress and coincided with the increased LTP staining. All obtained data suggest possible functions of LTPs in pea roots. We assume that these proteins can participate in stress-induced pea root suberization or in transport of phloem lipid molecules. Salt stress increased ABA immunostaining in pea root cells but its localization was different from that of the LTPs. Thus, we failed to confirm the hypothesis regarding the direct influence of ABA on the level of LTPs in the salt-stressed root cells.

When nutrition and allergy collide: the rise of anaphylaxis to plant foods.

Interest in nutrition is increasing, but in the world of internet health gurus, whilst the nutritional benefits of fruits and vegetables are extolled, wheat is often vilified. This review will assess the positive nutritional effects of plant foods in relation to allergy prevention, the effectiveness of gluten-avoidance and the likelihood of anaphylaxis to fruits and vegetables. Although the numbers of people who report gluten sensitivity is rising, hard evidence of mass sensitivity to gluten is scant. Also, the avoidance of wheat containing foods could lead to nutritional imbalance and effects on the gut microbiome. The evidence that fruits and vegetables have a protective effect on the development of allergy is inconsistent, although fruit juices may promote beneficial changes to gut microflora. Fruits and vegetables can cause severe allergic reactions, especially due to the presence of lipid transfer proteins, but this is not just a Mediterranean phenomenon, and not limited to peaches. These findings emphasise the importance of a keeping an open mind about reported reactions to plant foods, to ensure the correct diagnosis is made and nutrition is optimised to prevent any adverse effects of avoidance on the gut microbiome.

EVOLUTION OF THE ALLERGENIC POTENTIAL IN PEACH AND NECTARINE FRUITS DURING RIPENING

According to recent epidemiological studies, in many countries food allergies increased strongly during recent decades. Allergies to fruits represent also an emerging problem and studies should be addressed to identify allergens, evaluate the allergenic potential of different species and varieties and, possibly, produce hypoallergenic fruits. In peach, the major allergen has been identified as a Lipid Transfer Protein (LTP) and in the present research the evolution of the allergenic potential of different peach and nectarine varieties has been monitored throughout ripening and in relation to postharvest treatments. Fruits of peach cv. 'Royal Gemm', 'Zorzi', of nectarine cv. 'Rita Star', 'Early Giant' and 'Maria Dorata', and of flat type (Platicarpa) were harvested in correspondence of commercial ripeness and allowed to ripen at room temperature or stored at 4°C for 3 weeks. Northern blot analyses were carried out on total RNA extracted from epicarp and mesocarp to study Pp-LTP1 gene expression. Immunological studies were performed by means of a polyclonal antibody raised against the purified protein. Expression analysis showed that Pp-LTP1 transcripts accumulated only in the epicarp. With the exception of cv. 'Rita Star' the strongest accumulations have been detected in epicarp of all varieties at harvest. With the exception of Platicarpa, a decreasing trend of expression was observed in fruits kept in air and at 4°C. Western blots revealed the presence of LTP only in epicarp of all studied varieties, but not in 'Rita Star', and showed that the protein markedly increased in full ripe fruits maintained in air. This might indicate the presence of a lag between gene transcription and accumulation of secreted functional LTP. According to these results, cv. 'Rita Star' appears to be a variety with a reduced allergenic potential.

Intracellular localization of a lipid transfer protein in Vigna unguiculata seeds

Lipid transfer proteins (LTP) facilitate transfer of lipids between membranes in vitro. Up to now, they have been found to be localized basically in the plant cell wall and in compartments linked to lipid metabolism, such as glyoxysomes. Accordingly, LTP are considered to be involved in the plant defence against pathogen microbes and lipid metabolism. We herein show, by immunoelectron microscopy, that besides the cell wall, LTP are localized in the lumen of organelles which we suggest to be the protein storage vacuoles, as well as in vesicles similar to the lipid‐containing ones and in the extracellular space of Vigna unguiculata seeds. To further characterize these organelles, we performed subcellular fractionation of membranes isolated from imbibed seeds on a sucrose‐density gradient. The analysis of these fractions revealed that the lightest membrane vesicles, derived probably from PSV, contain LTP, α‐TIP and K+ independent PPiase, but not γ‐TIP and K+ stimulated PPiase. The presence of LTP and vicilins (typical storage protein) in the lumen of these vesicles was confirmed by immunoelectron microscopy. Taken together, the data suggest that the intracellular LTP in the V. unguiculata seeds are localized in protein storage vacuoles and in lipid‐containing vesicles.

Effect of membrane phospholipid composition and fluidity on rat liver plasma membrane tyrosine kinase activity

1. 1. The effect of membrane phospholipid composition and fluidity on tyrosine kinase activity was investigated in rat liver plasma membranes. 2. 2. The phospholipid composition has been modified by in vitro enrichment of plasma membranes with different phospholipids in the presence of lipid transfer proteins and by partial delipidation with exogenous phospholipases A2, C and D and subsequent enrichment with phosphatidylglycerol. 3. 3. Phosphadidylglycerol and dioleoylglycerophosphocholine caused dramatic elevation of this activity, while phosphatidylserine and phosphatidylethanolamine were less effective. Enrichment with dipalmitoylglycerophosphocholine and sphingomyeline reduced tyrosine kinase activity.

Phospholipid dependence of rat liver microsomal acyl:CoA synthetase and acyl-CoA:1-acyl-sn-glycero-3-phosphocholine O-acyltransferase.

Investigations were performed on the influence of the phospholipid composition and physicochemical properties of the rat liver microsomal membranes on acyl-CoA synthetase and acyl-CoA:1-acyl-sn-glycero-3-phosphocholine O-acyltransferase activities. The phospholipid composition of the membranes was modified by incubation with different phospholipids in the presence of lipid transfer proteins or by partial delipidation with exogenous phospholipase C and subsequent enrichment with phospholipids. The results indicated that the incorporation of phosphatidylglycerol, phosphatidylserine and phosphatidylethanolamine induced a marked activation of acyl-CoA synthetase for both substrates used--palmitic and oleic acids. Sphingomyelin occurred as specific inhibitor for this activity especially for palmitic acid. Palmitoyl-CoA: and oleoyl-CoA: 1-acyl-sn-glycero-3-phosphocholine acyltransferase activities were found to depend on the physical state of the membrane lipids. The alterations in the membrane physical state were estimated using two different fluorescent probes--1,6-diphenyl-1,3,5-hexatriene and pyrene. In all cases of membrane fluidization this activity was elevated. On the contrary, in more rigid membranes obtained by incorporation of sphingomyelin and dipalmitoylphosphatidylcholine, acyltransferase activity was reduced for both palmitoyl-CoA and oleoyl-CoA. We suggest a certain similarity in the way of regulation of membrane-bound acyltransferase and phospholipase A2 which both participate in the deacylation-reacylation cycle.

Effect of lipid transfer protein on plasma lipids, apolipoproteins and metabolism of high-density lipoprotein cholesteryl ester in the rat

The role of human plasma lipid transfer protein (LTP) in lipoprotein metabolism was studied in the rat, a species without endogenous cholesteryl ester and triacylglycerol transfer activity. Partially purified human LTP was injected intravenously into rats. The plasma activity was between 1.5- and 4-fold that of human plasma during the experiments. 6 h after the injection of LTP, a significant increase in serum apoB, and no significant changes in serum total cholesterol, free cholesterol, triacylglycerols, apoA-I, apoE, or apoA-IV were noted. Cholesterol was increased in very-low density and low-density lipoproteins (VLDL and LDL) and decreased in large-sized apoE-rich HDL. ApoA-I-containing particles with a size smaller than in normal rats were present in serum of LTP-treated rats. The mean diameter of HDL particles decreased and apoE, normally present on large-sized HDL, was present on smaller sized particles. The metabolic fate of cholesteryl ester, originally associated with HDL, was studied by injection of [ 3H]cholesteryl linoleyl ether-labelled apoA-I-rich HDL in the absence and in the presence of LTP. The disappearance of [ 3H]cholesteryl linoleyl ether, injected as part of apoA-I-rich HDL, from serum was increased in the LTP-treated rats; the t 1 2 changed from 3.9 to 2.2 h, resulting in an increased accumulation of [ 3H]cholesteryl linoleyl ether in the liver. This can be explained by the redistribution of HDL [ 3H]cholesteryl linoleyl ether to VLDL and LDL in the presence of LTP, leading to the combined contribution of VLDL, LDL and HDL to the hepatic uptake. The present findings show profound effects of LTP on the chemical composition of HDL subspecies, the size of HDL and on the plasma turnover and hepatic uptake of cholesteryl esters originally present in apo A-I-rich HDL.

Phospholipid uptake by Plasmodium knowlesi infected erythrocytes

The uptake of phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylserine (PS) in Plasmodium knowlesi infected erythrocytes has been studied. Whereas uptake of phospholipids, in the absence of phospholipid transfer proteins, is negligible in control cells, the infected cells can incorporate considerable amounts of added phospholipids. The uptake is enhanced by the presence of lipid transfer proteins. Doubly labeled [ 3H]oleate, [ 14C]choline) PC does not undergo any appreciable remodelling following uptake, which strongly suggests that plasma PC is used as such for the biogenesis of the parasite membranes. Transport of extracellularly offered PS and PE towards the intraerythrocytic parasite and utilization of these lipids by the parasite are confirmed by the observation that these lipids are converted into respectively PE and PC. The extent and rate of these conversions depend on the way the phospholipids are introduced into the infected cells.

Changes in lipid and apolipoprotein composition of pig lipoproteins facilitated by rabbit lipid transfer protein

A lipid transfer protein has been purified from the lipoprotein-free fraction of rabbit plasma. Rabbit lipid transfer protein, which was purified 600–700-fold with a 4% recovery, has an apparent M r. of 68000 and facilitates the transfer of isotopically labelled cholesterol ester, triacylglycerol and phosphatidylcholine between low-density lipoprotein (LDL) and high-density lipoprotein (HDL). Rabbit lipid transfer protein, which appears to be very similar to the cholesteryl ester exchange protein previously purified from human plasma, was incubated with pig plasma at 37° C for up to 6 h. Analysis of very-low-density lipoprotein (VLDL, d < 1.006 g/ml), LDL ( d 1.019−1.063 g/ml) and HDL ( d 1.090−1.21 g/ml) after incubation showed that lipid transfer protein had a marked effect on the composition of the lipoprotein classes. The VLDL became enriched with cholesteryl ester and depleted of triacylglycerol. The LDL and HDL became enriched with triacylglycerol. In addition to these changes in lipid composition there were also changes in apolipoprotein composition. The most prominent change in apolipoprotein distribution was a marked increase in the apolipoprotein E content of LDL which was observed only after incubation in the presence of lipid transfer protein.

Incubation of human lipid transfer protein with plasma from normal-fed and cholesterol-fed rats: Effect on the distribution of constituents between lipoprotein fractions

1. 1. Samples of rat plasma, in which activity of lecithin-cholesterol acyltransferase was inhibited, were incubated in vitro at 37°C for 6 hr in the presence and absence of a partially purified preparation of human lipid transfer protein (LTP). 2. 2. After the incubation gel filtration chromatography was used to separate plasma lipoproteins into multiple fractions which were individually assayed to obtain a complete profile of all constituents across the whole lipoprotein spectrum. 3. 3. When plasma from both normal and cholesterol-fed rats was incubated in the absence of LTP there were no changes in the distribution of any of the lipoprotein constituents between different fractions. 4. 4. When, however, normal plasma was incubated in the presence of LTP there was an obvious transfer of cholesteryl esters from high density lipoproteins (HDL) to very low density lipoproteins (VLDL) and of triglyceride from VLDL to HDL. 5. 5. The presence of LTP in incubations of plasma from cholesterol-fed rats, by contrast, resulted in only minimal redistributions of constituents.