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Food & Function Aug 2020Galactolipids, mainly monogalactosyl diglycerides and digalactosyl diglycerides are the main lipids found in the membranes of plants, algae and photosynthetic... (Review)
Review
Galactolipids, mainly monogalactosyl diglycerides and digalactosyl diglycerides are the main lipids found in the membranes of plants, algae and photosynthetic microorganisms like microalgae and cyanobacteria. As such, they are the main lipids present at the surface of earth. They may represent up to 80% of the fatty acid stocks, including a large proportion of polyunsaturated fatty acids mainly α-linolenic acid (ALA). Nevertheless, the interest in these lipids for nutrition and other applications remains overlooked, probably because they are dispersed in the biomass and are not as easy to extract as vegetable oils from oleaginous fruit and oil seeds. Another reason is that galactolipids only represent a small fraction of the acylglycerolipids present in modern human diet. In herbivores such as horses, fish and folivorous insects, galactolipids may however represent the main source of dietary fatty acids due to their dietary habits and digestion physiology. The development of galactolipase assays has led to the identification and characterization of the enzymes involved in the digestion of galactolipids in the gastrointestinal tract, as well as by microorganisms. Pancreatic lipase-related protein 2 (PLRP2) has been identified as an important factor of galactolipid digestion in humans, together with pancreatic carboxyl ester hydrolase (CEH). The levels of PLRP2 are particularly high in monogastric herbivores thus highlighting the peculiar role of PLRP2 in the digestion of plant lipids. Similarly, pancreatic lipase homologs are found to be expressed in the midgut of folivorous insects, in which a high galactolipase activity can be measured. In fish, however, CEH is the main galactolipase involved. This review discusses the origins and fatty acid composition of galactolipids and the physiological contribution of galactolipid digestion in various species. This overlooked aspect of lipid digestion ensures not only the intake of ALA from its main natural source, but also the main lipid source of energy for growth of some herbivorous species.
Topics: Amino Acid Sequence; Animals; Carboxylesterase; Carboxylic Ester Hydrolases; Digestion; Fatty Acids; Fishes; Galactolipids; Gastrointestinal Tract; Herbivory; Horses; Humans; Hydrolysis; Insecta; Lipase; Meat; Milk; Pancreas; Plant Leaves; Protein Conformation; Vegetables; alpha-Linolenic Acid
PubMed: 32687132
DOI: 10.1039/d0fo01040e -
Plant & Cell Physiology Jun 2018Monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG) together constitute approximately 80% of chloroplast lipids. Apart from facilitating the... (Review)
Review
Monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG) together constitute approximately 80% of chloroplast lipids. Apart from facilitating the photosynthesis light reaction in the thylakoid membrane, these two lipids are important for maintaining chloroplast morphology and for plant survival under abiotic stresses such as phosphate starvation and freezing. Recently it was shown that severe growth retardation phenotypes of the DGDG-deficient mutant dgd1 were due to jasmonate overproduction, linking MGDG and DGDG homeostasis with phytohormone production and suggesting MGDG as a major substrate for jasmonate biosynthesis. Induction of jasmonate synthesis and jasmonic acid (JA) signaling was also observed under conditions of phosphate starvation. We hypothesize that when DGDG is recruited to substitute for phospholipids in extraplastidic membranes during phosphate deficiency, the altered MGDG to DGDG ratio in the chloroplast envelope triggers the conversion of galactolipids into jasmonates. The conversion may contribute to rebalancing the MGDG to DGDG ratio rapidly to maintain chloroplast shape, and jasmonate production can reduce the growth rate and enhance predator deterrence. We also hypothesize that other conditions, such as suppression of dgd1 phenotypes by trigalactosyldiacylglycerol (tgd) mutations, may all be linked to altered jasmonate production, indicating that caution should be exercised when interpreting phenotypes caused by conditions that may alter the MGDG to DGDG ratio at the chloroplast envelope.
Topics: Chloroplasts; Cyclopentanes; Freezing; Galactolipids; Oxylipins; Phenotype; Phosphates; Photosynthesis; Plant Growth Regulators; Plants; Signal Transduction; Stress, Physiological
PubMed: 29727004
DOI: 10.1093/pcp/pcy088 -
Recent Patents on Food, Nutrition &... Jan 2009Galactolipids are a class of compounds widely found in the plant kingdom, including edible plants, and are an important part of the cell membranes. Galactolipids in... (Review)
Review
Galactolipids are a class of compounds widely found in the plant kingdom, including edible plants, and are an important part of the cell membranes. Galactolipids in plants consists mainly of monogalactosyldiacylglycerols and digalactosyldiacylglycerols containing one or two saturated and/or unsaturated fatty acids linked to the glycerol moiety. Several galactolipids have been shown to possess in vitro and/or in vivo anti-tumor promoting activity and anti-inflammatory activity. Recently, it has been demonstrated that the galactolipid, 1,2-di-O-alpha-linolenoyl-3-O-beta-D-galactopyranosyl-sn-glycerol (1), may be important for the anti-inflammatory activity of dog rose (Rosa canina), a medicinal plant with documented effect on anti-inflammatory diseases such as arthritis. This galactolipid also occurs in relative high concentrations in certain legumes (e.g., common bean, pea), leaf vegetables (e.g., kale, leek, parsley, perilla and spinach), stem vegetables (e.g., asparagus, broccoli, brussels sprouts), and fruit vegetables (e.g., chilli, bell pepper, pumpkin). Furthermore, compound 1 has been isolated from spinach and several medicinal plants by bioassay-guided fractionation as a galactolipid with possible cancer preventive effects. In this review, the bioactivity of galactolipids is discussed and their potential role in human diet as important nutraceuticals. Moreover, recent patents on the bioactivity of specific galactolipids and inventions making use of this knowledge are presented and discussed.
Topics: Anti-Inflammatory Agents; Antineoplastic Agents, Phytogenic; Biological Availability; Cell Membrane; Galactolipids; Plants, Medicinal; Vegetables
PubMed: 20653526
DOI: 10.2174/2212798410901010050 -
Trends in Plant Science Mar 2002Chloroplast membranes contain high levels of the galactolipids monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG). The isolation of the genes... (Review)
Review
Chloroplast membranes contain high levels of the galactolipids monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG). The isolation of the genes involved in the biosynthesis of MGDG and DGDG, and the identification of galactolipid-deficient Arabidopsis mutants has greatly facilitated the analysis of galactolipid biosynthesis and function. Galactolipids are found in X-ray structures of photosynthetic complexes, suggesting a direct role in photosynthesis. Furthermore, galactolipids can substitute for phospholipids, as suggested by increases in the galactolipid:phospholipid ratio after phosphate deprivation. The ratio of MGDG to DGDG is also crucial for the physical phase of thylakoid membranes and might be regulated.
Topics: Arabidopsis; Carbohydrate Sequence; Diglycerides; Galactolipids; Glycolipids; Molecular Sequence Data; Mutation; Phospholipids; Photosynthesis; Seeds; Thylakoids
PubMed: 11906834
DOI: 10.1016/s1360-1385(01)02216-6 -
Biochimica Et Biophysica Acta Dec 2002Myelination is a developmentally regulated process whereby myelinating glial cells elaborate large quantities of a specialized plasma membrane that ensheaths axons. The... (Review)
Review
Myelination is a developmentally regulated process whereby myelinating glial cells elaborate large quantities of a specialized plasma membrane that ensheaths axons. The myelin sheath contains an unusual lipid composition in that the glycolipid galactosylceramide (GalC) and its sulfated form sulfatide constitute a large proportion of the total lipid mass. These glycolipids have been implicated in a range of developmental processes such as cell differentiation and myelination initiation, but analyses of mice lacking UDP-galactose:ceramide galactosyltransferase (CGT), the enzyme required for myelin galactolipid synthesis, have more recently demonstrated that the galactolipids more subtly regulate myelin formation. The CGT mutants display a delay in myelin maturation and axo-glial interactions develop abnormally. By interbreeding the CGT mutants with mice that lack myelin-associated glycoprotein, it has been shown that these specialized myelin lipids and proteins act in concert to promote axo-glial adhesion during myelinogenesis. The analysis of the CGT mutants is helping to clarify the roles myelin galactolipids play in regulating the development, and ultimately the function of the myelin sheath.
Topics: Animals; Axons; Central Nervous System; Galactolipids; Galactosyltransferases; Ganglioside Galactosyltransferase; Intercellular Junctions; Myelin Sheath; Myelin-Associated Glycoprotein; Neuroglia; Neurons; Oligodendroglia
PubMed: 12417425
DOI: 10.1016/s0304-4165(02)00410-5 -
The Journal of General and Applied... Sep 2022Arabidopsis thaliana monogalactosyldiacylglycerol synthase 1 (AtMGD1) and digalactosyldiacylglycerol synthase 2 (AtDGD2) genes introduced into a Bacillus subtilis...
Arabidopsis thaliana monogalactosyldiacylglycerol synthase 1 (AtMGD1) and digalactosyldiacylglycerol synthase 2 (AtDGD2) genes introduced into a Bacillus subtilis chromosome with disrupted galE, which encodes UDP-glucose 4-epi merase, enabled the mutant to produce monogalactosyldiacylglycerol. When galE mutant cells are cultivated in galactose containing medium they show ab normal morphology. This phenotype is correlated with a decrease in the amount of glucolipids. Nucleoids of the ugtP and galE mutants were stained by propidium iodide, which does not permeate intact cell membranes, whereas nucleoids of wild type and of a pssA mutant we examined were not stained. Expression of the AtMGD1 gene in a ugtP galE double mutant restored cell membrane integrity. Expression of galactolipid synthase genes from a multi-copy plasmid, pDGHisN4, allowed higher production of galactolipids. Activation of the extracytoplasmic function sigma factors SigM, SigV, and SigX, in the ugtP mutant was decreased by expression of AtMGD1, and SigX activity was strongly repressed when both AtMGD1 and AtDGD2 genes were expressed in the mutant. We conclude that the number of sugars that bind to diacylglycerol - rather than the exact sugar species - is important for glycolipid function in B. subtilis.
Topics: Arabidopsis; Bacillus subtilis; Galactolipids; Sigma Factor
PubMed: 35370229
DOI: 10.2323/jgam.2021.08.002 -
Plant & Cell Physiology Jun 2019Etioplasts developed in angiosperm cotyledon cells in darkness rapidly differentiate into chloroplasts with illumination. This process involves dynamic transformation of...
Etioplasts developed in angiosperm cotyledon cells in darkness rapidly differentiate into chloroplasts with illumination. This process involves dynamic transformation of internal membrane structures from the prolamellar bodies (PLBs) and prothylakoids (PTs) in etioplasts to thylakoid membranes in chloroplasts. Although two galactolipids, monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG), are predominant lipid constituents of membranes in both etioplasts and chloroplasts, their roles in the structural and functional transformation of internal membranes during etioplast-to-chloroplast differentiation are unknown. We previously reported that a 36% loss of MGDG by an artificial microRNA targeting major MGDG synthase (amiR-MGD1) only slightly affected PLB structures but strongly impaired PT formation and protochlorophyllide biosynthesis. Meanwhile, strong DGDG deficiency in a DGDG synthase mutant (dgd1) disordered the PLB lattice structure in addition to impaired PT development and protochlorophyllide biosynthesis. In this study, thylakoid biogenesis after PLB disassembly with illumination was strongly perturbed by amiR-MGD1. The amiR-MGD1 expression impaired the accumulation of Chl and the major light-harvesting complex II protein (LHCB1), which may inhibit rapid transformation from disassembled PLBs to the thylakoid membrane. As did amiR-MGD1 expression, dgd1 mutation impaired the accumulation of Chl and LHCB1 during etioplast-to-chloroplast differentiation. Furthermore, unlike in amiR-MGD1 seedlings, in dgd1 seedlings, disassembly of PLBs after illumination was retarded. Because DGDG but not MGDG prefers to form the bilayer lipid phase in membranes, the MGDG-to-DGDG ratio may strongly affect the transformation of PLBs to the thylakoid membrane during etioplast-to-chloroplast differentiation.
Topics: Arabidopsis; Arabidopsis Proteins; Cell Membrane; Chloroplasts; Galactolipids; Galactosyltransferases; Thylakoids
PubMed: 30892620
DOI: 10.1093/pcp/pcz041 -
Plant Physiology and Biochemistry : PPB Nov 2021Membrane lipid remodeling helps in the efficient utilization of phosphorus (P) by replacing phospholipids with galactolipids during P deficiency. Previous studies have...
Membrane lipid remodeling helps in the efficient utilization of phosphorus (P) by replacing phospholipids with galactolipids during P deficiency. Previous studies have shown lipid remodeling in rice under P deficiency; however, main lipid classes did not show association with superior P-use-efficiency in rice genotypes. Here, diverse rice genotypes were extensively phenotyped in normal (NP) and low P (LP) conditions. Based on the phenotypic response to P deficiency, genotypes were identified as tolerant and sensitive. Further, bulks were generated differing in their physiological P-use-efficiency (PPUE) during LP condition. Shoot lipidome profiling of genotypes was performed and used to correlate the abundance of various lipid classes and their constituent species with the PPUE of the genotypes. Lipid remodeling was observed as a P-starvation-induced response in all the genotypes. However, neither total galacto- and phospholipids nor the lipid classes correlated with PPUE during P deficiency. However, the difference in PPUE in the two bulks correlated with specific lipid species of galactolipids (DGDG, MGDG). Further, DGDG34:3 had the highest Mol% among the differentially accumulated lipid species between the two bulks. Our study reveals the importance of specific galactolipids species in rice adaptation to P deficient soils and thus opens new targets for future research.
Topics: Galactolipids; Genotype; Membrane Lipids; Oryza; Phosphates; Plant Leaves
PubMed: 34628172
DOI: 10.1016/j.plaphy.2021.10.008 -
Proceedings of the National Academy of... Sep 2014The thylakoid membranes of oxygenic photosynthetic organisms are dominated by the galactolipids monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol...
The thylakoid membranes of oxygenic photosynthetic organisms are dominated by the galactolipids monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG). In cyanobacteria, MGDG is synthesized via monoglucosyldiacylglycerol (GlcDG). However, the putative epimerase involved in the conversion of GlcDG to MGDG has not been identified. Here we report the identification of the gene for the glucolipid epimerase (mgdE) by comparative genomic analysis. Knockout mutants of mgdE in Synechocystis sp. PCC 6803 lacked both MGDG and DGDG and accumulated GlcDG. The mutants did possess thylakoid membranes and showed normal maximal photosynthetic activity, albeit with reduced utilization of light energy. These results cast doubt on the long-standing belief that oxygenic photosynthesis is absolutely dependent on galactolipids.
Topics: Escherichia coli; Galactolipids; Mutation; Oxygen; Photosynthesis; Phylogeny; Racemases and Epimerases; Synechocystis; Thylakoids
PubMed: 25197079
DOI: 10.1073/pnas.1403708111 -
Journal of Bioenergetics and... Dec 1987Photosynthetic membranes of higher plant chloroplasts are composed primarily of polar, but uncharged, galactolipids unlike most mammalian membranes which contain large... (Review)
Review
Photosynthetic membranes of higher plant chloroplasts are composed primarily of polar, but uncharged, galactolipids unlike most mammalian membranes which contain large amounts of phosphatidylcholine. It is unclear what role(s) the galactolipids play in maintaining the differentiated thylakoid membranes, or in stabilizing the photosynthetically active enzyme complexes. Some of the membrane complexes show no lipid selectivity for maintaining structural or functional integrity. Others are poisoned or dissociated in the presence of high concentrations of a trace lipid class. The efficiency of energy transfer and the reconstitution of protein complexes into liposomes are dependent on the lipid class employed. The lipids are asymmetrically arranged along and across the thylakoid membranes but not as distinctly as the proteins.
Topics: Chloroplasts; Galactolipids; Glycolipids; Intracellular Membranes; Membrane Lipids; Photosynthesis; Plant Physiological Phenomena
PubMed: 3320041
DOI: 10.1007/BF00762303