Phospholipid and glycerolipid metabolism as potential diagnostic biomarkers for acute pancreatitis.

BACKGROUND: Acute pancreatitis (AP) is characterized as a systemic inflammatory condition posing challenges in diagnosis and prognosis assessment. Lipid metabolism abnormalities, especially triacylglycerol (TAG) levels, have been reported, indicating their potential as biomarkers in acute pancreatitis. However, the performance of the TAG cycle, including phospholipid and glycerolipid metabolism, in AP patients has not yet been reported. METHODS: This study enrolled 91 patients with acute biliary pancreatitis (ABP), 27 with hyperlipidaemic acute pancreatitis (HLAP), and 58 healthy controls (HCs), and their plasma phospholipid and glycerolipid levels were analyzed through liquid chromatography‒mass spectrometry. The phospholipid and glycerolipid contents of plasma collected from AP patients on the first, third, and seventh days of hospitalization were also measured. An orthogonal partial least squares discriminant analysis model served to differentiate the ABP, HLAP and HC groups, and potentially diagnostic lipids were evaluated via receiver operating characteristic curves in both the test and validation sets. Correlations between clinical data and lipids were conducted using Spearman's method. Clustering via the 'mfuzz' R package and the Kruskal‒Wallis H test were conducted to monitor changes during hospitalization. RESULTS: Compared with those in HCs, the levels of phosphatidylcholine (PC), phosphatidylethanolamine (PE), and phosphatidic acid (PA) were lower in AP patients, whereas the levels of phosphatidylinositol (PI) and phosphatidylglycerol (PG) showed the opposite trend. Interestingly, TAG levels were positively correlated with white blood cell counts in ABP patients, and TAGs containing 44-55 carbon atoms were highly correlated with plasma TAG levels in HLAP patients. Phospholipid levels exhibited an inverse correlation with AP markers, in contrast to glycerolipids, which demonstrated a positive correlation with these markers. Additionally, PE (O-16:0/20:4) and PE (18:0/22:6) emerged as potential biomarkers because of their ability to distinguish ABP and HLAP patients from HCs, showing area under the curve (AUC) values of 0.932 and 0.962, respectively. PG (16:0/18:2), PG (16:0/20:4), PE (P-16:0/20:2), PE (P-18:2/18:2), PE (P-18:1/20:3), PE (P-18:1/20:4), PE (O-16:0/20:4), and TAG (56:6/FA18:0) were significantly changed in ABP patients who improved. For HLAP patients, PC (18:0/20:3), TAG (48:3/FA18:1), PE (P-18:0/16:0), and TAG (48:4/FA18:2) showed different trends in patients with improvement and deterioration, which might be used for prognosis. CONCLUSIONS: Phospholipids and glycerolipids were found to be potential biomarkers in acute pancreatitis, which offers new diagnostic and therapeutic insights into this disease.

Probing Glycerolipid Metabolism using a Caged Clickable Glycerol-3-Phosphate Probe.

In this study, we present the probe SATE-G3P-N3 as a novel tool for metabolic labeling of glycerolipids (GLs) to investigate lipid metabolism in yeast cells. By introducing a clickable azide handle onto the glycerol backbone, this probe enables general labeling of glycerolipids. Additionally, this probe contains a caged phosphate moiety at the glycerol sn-3 position to not only facilitate probe uptake by masking negative charge but also to bypass the phosphorylation step crucial for initiating phospholipid synthesis, thereby enhancing phospholipid labeling. The metabolic labeling activity of the probe was thoroughly assessed through cellular fluorescence microscopy, mass spectrometry (MS), and thin-layer chromatography (TLC) experiments. Fluorescence microscopy analysis demonstrated successful incorporation of the probe into yeast cells, with labeling predominantly localized at the plasma membrane. LCMS analysis confirmed metabolic labeling of various phospholipid species (PC, PS, PA, PI, and PG) and neutral lipids (MAG, DAG, and TAG), and GL labeling was corroborated by TLC. These results showcased the potential of the SATE-G3P-N3 probe in studying GL metabolism, offering a versatile and valuable approach to explore the intricate dynamics of lipids in yeast cells.

Genome-wide association identifies a BAHD acyltransferase activity that assembles an ester of glucuronosylglycerol and phenylacetic acid.

Genome-wide association studies (GWAS) are an effective approach to identify new specialized metabolites and the genes involved in their biosynthesis and regulation. In this study, GWAS of Arabidopsis thaliana soluble leaf and stem metabolites identified alleles of an uncharacterized BAHD-family acyltransferase (AT5G57840) associated with natural variation in three structurally related metabolites. These metabolites were esters of glucuronosylglycerol, with one metabolite containing phenylacetic acid as the acyl component of the ester. Knockout and overexpression of AT5G57840 in Arabidopsis and heterologous overexpression in Nicotiana benthamiana and Escherichia coli demonstrated that it is capable of utilizing phenylacetyl-CoA as an acyl donor and glucuronosylglycerol as an acyl acceptor. We, thus, named the protein Glucuronosylglycerol Ester Synthase (GGES). Additionally, phenylacetyl glucuronosylglycerol increased in Arabidopsis CYP79A2 mutants that overproduce phenylacetic acid and was lost in knockout mutants of UDP-sulfoquinovosyl: diacylglycerol sulfoquinovosyl transferase, an enzyme required for glucuronosylglycerol biosynthesis and associated with glycerolipid metabolism under phosphate-starvation stress. GGES is a member of a well-supported clade of BAHD family acyltransferases that arose by duplication and neofunctionalized during the evolution of the Brassicales within a larger clade that includes HCT as well as enzymes that synthesize other plant-specialized metabolites. Together, this work extends our understanding of the catalytic diversity of BAHD acyltransferases and uncovers a pathway that involves contributions from both phenylalanine and lipid metabolism.

Low-Salt Diet Regulates the Metabolic and Signal Transduction Genomic Fabrics, and Remodels the Cardiac Normal and Chronic Pathological Pathways.

Low-salt diet (LSD) is a constant recommendation to hypertensive patients, but the genomic mechanisms through which it improves cardiac pathophysiology are still not fully understood. Our publicly accessible transcriptomic dataset of the left ventricle myocardium of adult male mice subjected to prolonged LSD or normal diet was analyzed from the perspective of the Genomic Fabric Paradigm. We found that LSD shifted the metabolic priorities by increasing the transcription control for fatty acids biosynthesis while decreasing it for steroid hormone biosynthesis. Moreover, LSD remodeled pathways responsible for cardiac muscle contraction (CMC), chronic Chagas (CHA), diabetic (DIA), dilated (DIL), and hypertrophic (HCM) cardiomyopathies, and their interplays with the glycolysis/glucogenesis (GLY), oxidative phosphorylation (OXP), and adrenergic signaling in cardiomyocytes (ASC). For instance, the statistically (p < 0.05) significant coupling between GLY and ASC was reduced by LSD from 13.82% to 2.91% (i.e., -4.75×), and that of ASC with HCM from 10.50% to 2.83% (-3.71×). The substantial up-regulation of the CMC, ASC, and OXP genes, and the significant weakening of the synchronization of the expression of the HCM, CHA, DIA, and DIL genes within their respective fabrics justify the benefits of the LSD recommendation.

In Vivo Monitoring of Glycerolipid Metabolism in Animal Nutrition Biomodel-Fed Smart-Farm Eggs.

Although many studies have examined the biochemical metabolic pathways by which an egg (egg yolk) lowers blood lipid levels, data on the molecular biological mechanisms that regulate and induce the partitioning of hepatic glycerolipids are missing. The aim of this study was to investigate in vivo monitoring in four study groups using an animal nutrition biomodel fitted with a jugular-vein cannula after egg yolk intake: CON (control group, oral administration of 1.0 g of saline), T1 (oral administration of 1.0 g of pork belly fat), T2 (oral administration of 1.0 g of smart-farm egg yolk), and T3 (oral administration of T1 and T2 alternately every week). The eggs induced significant and reciprocal changes in incorporating 14C lipids into the total glycerolipids and releasing 14CO2, thereby regulating esterification and accelerating oxidation in vivo. The eggs increased phospholipid secretion from the liver into the blood and decreased triacylglycerol secretion by regulating the multiple cleavage of fatty acyl-CoA moieties' fluxes. In conclusion, the results of the current study reveal the novel fact that eggs can lower blood lipids by lowering triacylglycerol secretion in the biochemical metabolic pathway of hepatic glycerolipid partitioning while simultaneously increasing phospholipid secretion and 14CO2 emission.

Structures, functions, and syntheses of glycero-glycophospholipids.

Biological membranes consist of integral and peripheral protein-associated lipid bilayers. Although constituent lipids vary among cells, membrane lipids are mainly classified as phospholipids, glycolipids, and sterols. Phospholipids are further divided into glycerophospholipids and sphingophospholipids, whereas glycolipids are further classified as glyceroglycolipids and sphingoglycolipids. Both glycerophospholipids and glyceroglycolipids contain diacylglycerol as the common backbone, but their head groups differ. Most glycerolipids have polar head groups containing phosphate esters or sugar moieties. However, trace components termed glycero-glycophospholipids, each possessing both a phosphate ester and a sugar moiety, exist in membranes. Recently, the unique biological activities of glycero-glycophospholipids have attracted considerable attention. In this review, we describe the structure, distribution, function, biosynthesis, and chemical synthetic approaches of representative glycero-glycophospholipids-phosphatidylglucoside (PtdGlc) and enterobacterial common antigen (ECA). In addition, we introduce our recent studies on the rare glycero-glyco"pyrophospho"lipid, membrane protein integrase (MPIase), which is involved in protein translocation across biomembranes.

Exploring the fates and molecular changes of different diacylglycerol-rich lipids during in vitro digestion.

This study aimed to support the pursuit of healthy oils and investigate the relationships between lipid compositions and digestion fates of diacylglycerol (DAG)-rich lipids using an in vitro digestion model. Soybean-, olive-, rapeseed-, camellia-, and linseed-based DAG-rich lipids (termed SD, OD, RD, CD, and LD, respectively) were selected. These lipids exhibited identical lipolysis degrees (92.20-94.36 %) and digestion rates (0.0403-0.0466 s-1). The lipid structure (DAG or triacylglycerol) was a more important factor affecting the lipolysis degree than other indices (glycerolipid composition and fatty acid composition). For RD, CD and LD with similar fatty acid compositions, the same fatty acid had different release levels, probably due to their different glycerolipid compositions (causing different distributions of the fatty acid in UU-DAG, USa-DAG and SaSa-DAG; U: unsaturated fatty acids, Sa: saturated fatty acids). This study provides insights into the digestion behaviors of different DAG-rich lipids and supports their food or pharmaceutical applications.

Molecular Mechanism for Hepatic Glycerolipid Partitioning of n-6/n-3 Fatty Acid Ratio in an Obese Animal Biomodels.

The n-6/n-3 metabolic pathway associated with hepatic glycerolipid portioning plays a key role in preventing obesity. In this nutrition metabolism study, we used in vivo monitoring techniques with 40 obese male Sprague-Dawley strain rats attached with jugular-vein cannula after obesity was induced by a high-fat diet to determine the molecular mechanism associated with hepatic glycerolipid partitioning involving the n-6/n-3 metabolic pathway. Rats were randomly assigned to four groups (10 animals per group), including one control group (CON, n-6/n-3 of 71:1) and three treatment groups (n-6/n-3 of 4:1, 15:1 and 30:1). They were fed with experimental diets for 60 days. Incorporation rates of [14C]-labeling lipid into glycerolipid in the liver were 28.87−37.03% in treatment groups fed with diets containing an n-6/n-3 ratio of 4:1, 15:1 and 30:1, which were significantly (p < 0.05) lower than that in the CON (40.01%). However, 14CO2 emission % of absorbed dose showed the opposite trend. It was significantly (p < 0.05) higher in a treatment groups (n-6/n-3 of 4:1, 15:1 and 30:1, 30.35−45.08%) than in CON (27.71%). Regarding the metabolic distribution of glycerolipid to blood from livers, phospholipid/total glycerolipid (%) was significantly (p < 0.05) lower in CON at 11.04% than in treatment groups at 18.15% to 25.15%. Moreover, 14CO2/[14C]-total glycerolipid (%) was significantly (p < 0.05) higher in treatment groups at 44.16−78.50% than in CON at 39.50%. Metabolic distribution of fatty acyl moieties flux for oxidation and glycerolipid synthesis in the liver were significantly (p < 0.05) better in order of 4:1 > 15:1 > 30:1 than in the CON. Our data demonstrate that n-6/n-3 of 4:1 could help prevent obesity by controlling the mechanism of hepatic partitioning through oxidation and esterification of glycerolipid in an obese animal biomodel.

Evaluation of changes in egg yolk lipids during storage based on lipidomics through UPLC-MS/MS.

A comprehensive UPLC-MS/MS-based lipidomics analysis of egg yolk at different storage periods was performed. Through the analysis, 836 lipid species from 27 subclasses were detected, including 159 significantly different lipid species. Glycerolipids (GL) and glycerophospholipids (GP) were the most abundant lipids, followed by fatty acyls (FA), sphingolipids (SP), sterol lipids (ST), and prenol lipids (PR). PCA and OPLS-DA showed that egg yolk lipids changed significantly with prolonged storage. Moreover, glycerophospholipid metabolism and glycerolipid metabolism were key metabolic pathways, as phosphatidic acid (PA), lysophosphatidic acid (LPA), and diglyceride (DG) were key lipid metabolites in the related metabolic pathways of egg yolk during storage. Furthermore, egg yolk quality changed the most when stored up to 21 days. Our study establishes a foundation for the quality control and the lipid oxidation mechanism of eggs during storage.

Flavonoids from Sedum aizoon L. inhibit Botrytis cinerea by negatively affecting cell membrane lipid metabolism.

Botrytis cinerea is a highly destructive and widespread phytopathogen in fruits. The widespread use of chemical antifungal agents on fruits has aided in disease control while their long-term use has resulted in the emergence of resistant fungal strains. Flavonoids have a specific antifungal effect. The inhibitory effect and underlying mechanism of flavonoids from Sedum aizoon L. (FSAL) on B. cinerea were determined in this study. The results showed that the minimum inhibitory concentration of FSAL against B. cinerea was 1.500 mg/mL. FSAL treatment caused leakage of macromolecules such as nucleic acids, led to accumulation of malondialdehyde and relative oxygen species, and disrupted the ultrastructure of B. cinerea. The transcriptome results indicated that compared with the control group, there were 782 and 1330 genes identified as being substantially upregulated and downregulated, respectively, in the FSAL-treated group. The identified genes and metabolites were mostly involved in redox processes and glycerolipid and amino acid metabolism pathways. FSAL offer a promising choice for food prevention and safety. KEY POINTS: • FSAL negatively affects the glycerolipid metabolism of B. cinerea • FSAL minimum inhibitory concentration against B. cinerea was 1.500 mg/mL • FSAL could be utilized as a new prevention strategy for gray mold in fruits.

LYSOPHOSPHATIDIC ACID ACYLTRANSFERASE 2 (LPAT2) is required for de novo glycerolipid biosynthesis, growth, and development in vegetative and reproductive tissues of Arabidopsis.

The Kennedy pathway is a highly conserved de novo glycerolipid biosynthesis pathway in prokaryotes and eukaryotes. In Arabidopsis, LYSOPHOSPHATIDIC ACID ACYLTRANSFERASE 2 (LPAT2) was assumed to catalyze a crucial reaction step of the endoplasmic reticulum (ER)-localized Kennedy pathway because of lethality in the lpat2-1 knockout mutant. However, whether this lethal phenotype was due to the essential role of the Kennedy pathway or LPAT2 as the key enzyme of the Kennedy pathway was unclear. By creating non-lethal LPAT2-knockdown mutants in Arabidopsis, we found that LPAT2 is required for phospholipid content and plant development in vegetative and reproductive growth. Functional in vivo reporter assays revealed that LPAT2 was ubiquitously expressed and localized to the ER, where de novo phospholipid biosynthesis takes place. Intriguingly, our lipid analysis revealed that LPAT2 suppression had different effects among the organs examined: phospholipid levels were decreased both in leaves and flowers and the effect was more pronounced in flowers, a non-photosynthetic organ enriched with phospholipids. Although seed size was reduced in the LPAT2 suppression lines, no remarkable effect was observed in the lipid content of mature siliques. Our results show that LPAT2 is involved in the ER-localized Kennedy pathway, and suggest that its contribution to de novo phospholipid biosynthesis may have organ selectivity.

Lipidomic analysis reveals the effect of passive smoking on facial skin surface lipid in females.

BACKGROUND: Smoking has toxic effects on the skin and can damage it. However, few studies have focused on the lipid profile changes of facial skin surface lipids (SSL) by passive smoking. METHOD: A cross-sectional analytical study was conducted on middle-aged females volunteered from Henan, China to participate in the study. A total of 20 passive smoking females and 20 non-passive smoking females were recruited for this study. The components of skin surface lipids were measured by ultra-performance liquid chromatography quadrupole time of flight mass spectrometry (UPLC-QTOF-MS). Multivariate data analysis and enrichment analysis were used to investigate the differences in facial SSL between passive and non-passive smoking females. RESULT: There were 1247 lipid entities identified in facial SSL between passive and non-passive smoking females. Significant differences in composition of facial SSL were observed between the two groups. After multivariate data analysis suggested, 28 significantly different lipids were identified and classified into four classes in SSL of the female cheeks. As well as 32 significantly different lipids were obtained in SSL of the female foreheads, which included three classes of lipids. Subsequent analysis revealed that the content of fatty acids (FA) in passive smoking females was significantly reduced and the content of glycerolipids (GL) and sphingolipids (SP) increased, compared with the control group. CONCLUSION: These results indicated that an increase in GLs and SPs of facial lipids and a decrease in FAs in passive smoking females. These changes in lipids might be associated with oxidative stress and interference with signaling pathways by substances in smoke. And passive smoking affected facial SSL and changed the content and metabolism of skin lipids.

Dynamic Changes in Membrane Lipid Metabolism and Antioxidant Defense During Soybean (Glycine max L. Merr.) Seed Aging.

Seed viability depends upon the maintenance of functional lipids; however, how membrane lipid components dynamically change during the seed aging process remains obscure. Seed storage is accompanied by the oxidation of membrane lipids and loss of seed viability. Understanding membrane lipid changes and their effect on the cell membrane during seed aging can contribute to revealing the mechanism of seed longevity. In this study, the potential relationship between oxidative stress and membrane lipid metabolism was evaluated by using a non-targeted lipidomics approach during artificial aging of Glycine max L. Merr. Zhongdou No. 27 seeds. We determined changes in reactive oxygen species, malondialdehyde content, and membrane permeability and assessed antioxidant system activity. We found that decreased non-enzymatic antioxidant contents and catalase activity might lead to reactive oxygen species accumulation, resulting in higher electrolyte leakage and lipid peroxidation. The significantly decreased phospholipids and increased glycerolipids and lysophospholipids suggested that hydrolysis of phospholipids to form glycerolipids and lysophospholipids could be the primary pathway of membrane metabolism during seed aging. Moreover, the ratio of phosphatidylcholine to phosphatidylethanolamine, double bond index, and acyl chain length of phospholipids were found to jointly regulate membrane function. In addition, the observed changes in lipid metabolism suggest novel potential hallmarks of soybean seed aging, such as diacylglycerol 36:4; phosphatidylcholine 34:2, 36:2, and 36:4; and phosphatidylethanolamine 34:2. This knowledge can be of great significance for elucidating the molecular mechanism underlying seed aging and germplasm conservation.

Metabolism-secretion coupling in glucose-stimulated insulin secretion.

Pancreatic ß-cells in the islets of Langerhans secrete insulin in response to blood glucose levels. Precise control of the amount of insulin secreted is of critical importance for maintaining systemic carbohydrate homeostasis. It is now well established that glucose induced production of ATP from ADP and the KATP channel closure elevate cytosolic Ca2+, triggering insulin exocytosis in ß-cells. However, for full activation of insulin secretion by glucose, other mechanisms besides Ca2+ elevation are needed. These mechanisms are the targets of current research and include intracellular metabolic pathways branching from glycolysis. They are metabolic pathways originating from the TCA cycle intermediates, the glycerolipid/free fatty acid cycle and the pentose phosphate pathway. Signaling effects of these pathways including degradation (removal) of protein SUMOylation, modulation of insulin vesicular energetics, and lipid modulation of exocytotic machinery may converge to fulfill insulin secretion, though the precise mechanisms have yet to be elucidated. This mini-review summarize recent advances in research on metabolic coupling mechanisms functioning in insulin secretion.

Multi-Omics Characterization of a Glycerolipid Metabolism-Related Gene Enrichment Score in Colon Cancer.

Background: Glycerolipid metabolism is involved in the genesis and progression of colon cancer. The current study aims at exploring the prognostic value and potential molecular mechanism of glycerolipid metabolism-related genes in colon cancer from the perspective of multi-omics. Methods: Clinical information and mRNA expression data of patients with colon cancer were obtained from The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases. Single-sample gene set enrichment analysis (ssGSEA) was applied to calculate the glycerolipid metabolism-related gene enrichment score (GLMS). Univariable and multivariable Cox regression analyses were used to study the prognostic value of GLMS in TCGA-COAD and GSE39582 cohorts. The molecular mechanism of the prognostic factor was investigated via immune cell infiltration estimation and correlation analysis of cancer hallmark pathways. Single-cell transcriptomic dataset GSE146771 was used to identify the cell populations which glycerolipid metabolism targeted on. Results: The GLMS was found to be associated with tumor location and consensus molecular types (CMSs) of colon cancer in TCGA-COAD cohort (P < 0.05). Patients in the low-GLMS group exhibited poorer overall survival (OS) in TCGA cohort (P = 0.03; HR, 0.63; 95% CI, 0.42-0.94), which was further validated in the GSE39582 dataset (P < 0.001; HR, 0.57; 95% CI, 0.43-0.76). The association between the GLMS and OS remained significant in the multivariable analysis (TCGA cohort: P = 0.04; HR, 0.64; 95% CI, 0.42-0.98; GSE39582 cohort: P < 0.001; HR, 0.60; 95% CI, 0.45-0.80). The GLMS was positively correlated with cancer hallmark pathways including bile acid metabolism, xenobiotic metabolism, and peroxisome and negatively correlated with pathways such as interferon gamma response, allograft rejection, apoptosis, and inflammatory response (P < 0.05). Increased immune infiltration and upregulated expression of immune checkpoints were observed in patients with lower GLMS (P < 0.05). Single-cell datasets verified the different distribution of GLMS in cell subsets, with significant enrichment of GLMS in malignant cells and Tprolif cells. Conclusion: We demonstrated that GLMS was a potential independent prognostic factor for colon cancer. The GLMS was also correlated with several cancer hallmark pathways, as well as immune microenvironment.

Lipid profile variations in high olecic acid peanuts by following different cooking processes.

High oleic acid (OA) peanut seed (PS), contains a higher ratio of oleic acid (C18:1) compared to general PS, which is favored by consumers due to its health benefits. However, comprehensive lipid metabolite profiles of high-OA PS, once they have been processed via domestic cooking methods, have never been produced. To establish a scientific guide for the selection of the most appropriate processing method for high-OA PS, lipidomics was performed to identify 706 lipid metabolites in high-OA PS following boiling, baking and frying, between the three groups, 75, 175 and 242 lipid metabolites were differentially expressed respectively. Additionally, 46 glycerolipids with C18:1 molecular were observed in the lipid profiles of the treatment groups compared to the raw sample. Further evaluation of seven lipid peroxides and six antioxidant status of each testing group suggested that boiled PS retained the highest levels of lipids and antioxidant activity. Following these findings, boiling appears to be an appropriate processing method when attempting to conserve the beneficial substances found in the PS. Finally, the levels of major free fatty acids present in high-OA PS, were jointly quantified by conventional methods (GC-MS) and lipidomic analysis. FA/C16:0 levels were similar, FA/C18:0, FA/C18:1 displayed opposite results, FA/C18:2 levels increased following frying and FA/C18:3 levels were down regulated once the PS was boiled. This indicates that GC-MS is a potential method of validation for the results of lipidomic analysis. Conclusively, this in depth understanding of lipid content in relation to domestic cooking methods has provided a foundation for the processing of high-OA peanut products.

Functional divergence of a pair of Arabidopsis phospho-base methyltransferases, PMT1 and PMT3, conferred by distinct N-terminal sequences.

In seed plants, phospho-base N-methyltransferase (PMT) catalyzes a key step in the biosynthesis pathway of phosphatidylcholine (PC), the most abundant phospholipid class. Arabidopsis thaliana possesses three copies of PMT, with PMT1 and PMT3 play a primary role because the pmt1 pmt3 double mutant shows considerably reduced PC content with a pale seedling phenotype. Although the function of PMT1 and PMT3 may be redundant because neither of the parental single mutants showed a similar mutant phenotype, major developmental defects and possible functional divergence of these PMTs underlying the pale pmt1 pmt3 seedling phenotype are unknown. Here, we show the major developmental defect of the pale seedlings in xylem of the hypocotyl with partial impairments in chloroplast development and photosynthetic activity in leaves. Although PMT1 and PMT3 are localized at the endoplasmic reticulum, their tissue-specific expression pattern was distinct in hypocotyls and roots. Intriguingly, the function of PMT3 but not PMT1 requires its characteristic N-terminal sequence in addition to the promoter because truncation of the N-terminal sequence of PMT3 or substitution with PMT1 driven by the PMT3 promoter failed to rescue the pale pmt1 pmt3 seedling phenotype. Thus, PMT3 function requires the N-terminal sequence in addition to its promoter, whereas the PMT1 function is defined by the promoter.

Analysis of XBP1 Contribution to Hyperosmolarity-Induced Lipid Synthesis.

The unfolded protein response (UPR) is a complex network of intracellular pathways that transmits signals from ER lumen and/or ER bilayer to the nuclear compartment in order to activate gene transcription. UPR is activated by the loss of ER capacities, known as ER stress, and occurs to restore ER properties. In this regard, glycerolipid (GL) synthesis activation contributes to ER membrane homeostasis and IRE1α-XBP1, one UPR pathway, has a main role in lipogenic genes transcription. Herein, we describe the strategy and methodology used to evaluate whether IRE1α-XBP1 pathway regulates lipid metabolism in renal epithelial cells subjected to hyperosmolar environment. XBP1s activity was hindered by blocking IRE1α RNAse activity and by impeding its expression; under these conditions, we determined GL synthesis and lipogenic enzymes expression.

The specific glycerolipid composition is responsible for maintaining the membrane stability of Physcomitrella patens under dehydration stress.

Land colonization is a major event in plant evolution. Little is known about the evolutionary characteristics of lipids during this process. Here, we proved that Physcomitrella patens, a bryophyte that appeared in the early evolution of terrestrial plants, has short-term desiccation resistance. The maintenance of membrane integrity is related to its specific glycerolipid composition and key genes for lipid metabolism. We analyzed 414 types of lipid molecules, and found that phospholipids accounted for 61.7%, mainly PC and PI; glycolipids accounted for only 26.5%, with a special MGDG molecular map. The most abundant MDGD, that is, MGDG34:6, contained rare 15- and 19-carbon acyl chains; the level of neutral lipids was higher. This was consistent with the results observed by TEM, with fewer lamellae and obvious lipid droplets. Slight dehydration accumulated a large number of TAG molecules, and severe dehydration degraded phospholipids and caused membrane leakage, but PA and MGDG fluctuated less. The key genes of lipid metabolism, DGAT and PAP, were actively transcribed, suggesting that PA was one of the main DAG sources for TAG synthesis. This work proves that Physcomitrella patens adopts high-constitutive PC and PI similar to plant seeds, abundant TAG, and its own specific MGDG to resist extreme dehydration. This result provides a new insight into the lipid evolution of early terrestrial plants against unfavorable terrestrial environments.

Role of Lipids of the Evergreen Shrub Ephedra monosperma in Adaptation to Low Temperature in the Cryolithozone.

Lipids are the fundamental components of cell membranes and they play a significant role in their integrity and fluidity. The alteration in lipid composition of membranes has been reported to be a major response to abiotic environmental stresses. Seasonal dynamics of membrane lipids in the shoots of Ephedra monosperma J.G. Gmel. ex C.A. Mey. growing in natural conditions of permafrost ecosystems was studied using HPTLC, GC-MS and ESI-MS. An important role of lipid metabolism was established during the autumn-winter period when the shoots of the evergreen shrub were exposed to low positive (3.6 °C), negative (-8.3 °C) and extremely low temperatures (-38.4 °C). Maximum accumulation of phosphatidic acid (PA), the amount of which is times times greater than the sum of phosphatidylcholine and phosphatidylethanolamine (PC + PE) was noted in shoots of E. monosperma in the summer-autumn period. The autumn hardening period (3.6 °C) is accompanied by active biosynthesis and accumulation of membrane lipids, a decrease of saturated 34:1 PCs, 34:1 PEs and 34:1 PAs, and an increase in unsaturated long-chain 38:5 PEs, 38:6 PEs, indicating that the adaptation of E. monosperma occurs not at the level of lipid classes but at the level of molecular species. At a further decrease of average daily air temperature in October (-8.3 °C) a sharp decline of PA level was registered. At an extreme reduction of environmental temperature (-38.4 °C) the content of non-bilayer PE and PA increases, the level of unsaturated fatty acids (FA) rises due to the increase of C18:2(Δ9,12) and C18:3(Δ9,12,15) acids and the decrease of C16:0 acids. It is concluded that changes in lipid metabolism reflect structural and functional reorganization of cell membranes and are an integral component of the complex process of plant hardening to low temperatures, which contributes to the survival of E. monosperma monocotyledonous plants in the extreme conditions of the Yakutia cryolithozone.