Degradation Of Membrane Lipids Research Articles

Remodeling of membrane lipids associated with ABA-induced desiccation tolerance in Physcomitrium patens

Pretreatment of Physcomitrium patens with abscisic acid (ABA) has been shown to induce desiccation tolerance. While previous research suggests that ABA-induced production of proteins and soluble sugars contributes to desiccation stress tolerance, additional mechanisms underlying this tolerance remain unclear. In this study, we found that ABA pretreatment led to increased levels of digalactosyl diacylglycerol (DGDG), phosphatidylcholine (PC), and phosphatidylinositol (PI), along with a decrease in monogalactosyl diacylglycerol (MGDG). These changes elevated the MGDG/DGDG and PC/phosphatidylethanolamine (PE) ratios, potentially stabilizing membranes and enhancing desiccation tolerance. Furthermore, ABA pretreatment effectively prevented membrane lipid degradation during desiccation and subsequent rehydration. These findings highlight ABA's role in desiccation tolerance through membrane lipid modulation, providing new insights into stress tolerance mechanisms in bryophytes.

Transcriptomic and metabolomic analysis of quality deterioration of postharvest okra fruit at different storage temperatures

Okra fruit have short postharvest potential and are susceptible to chilling injury (CI). To increase our understanding of the metabolism of okra fruit we have analyzed the transcriptomic and metabolomic changes of the fruit stored at 4, 10, and 22 ℃ for six days. Compared with 0 d, storage at 22 °C for 6 days, senescence and lignification of fruit were associated with upregulation of genes related to abscisic acid (ABA) synthesis and signal transduction (ZEP, NCED, AAO, PYR/PYL, PP2C), lignin synthesis (HCT, 4CL, CCR, CAD, F5H, COMT), and cellulose synthesis (CesA). Chilling injury of okra at 4 ℃ may be caused by the activation of the α-linolenic acid metabolic pathway and flavonoid synthesis pathway, compromised membrane integrity, and higher reactive oxygen species levels. Storage at 10 ℃ resulted in the downregulation of ABA synthesis, signal transduction, and lignin synthesis genes, inhibition of α-linolenic acid pathway metabolites, and the expression of membrane lipid degradation genes (PLD, PLA, lipase, DGK, LOX). Conversely, there was an upregulation of antioxidant enzymes (APX, AO, POD, Grx, MDHAR) and genes involved in the flavonoid synthesis pathway (C4H, CHS, CHI, F3H, ANS), and with their corresponding metabolites (pinocembrin, butin, epiafzelechin, catechin). These changes were associated with slower fruit senescence, indicating that 10 ℃ better maintained the physiological quality of okra fruit after harvest. Based on these findings, a network model was established to control the postharvest quality of okra fruit under different temperature treatments. This study explored the regulatory mechanism of okra at different temperatures at the molecular level and laid a theoretical foundation for improving the quality of postharvest okra and extending its shelf life.

Integrating Transcriptome and Metabolome Analysis Unveils the Browning Mechanism of Leaf Response to High Temperature Stress in Nicotiana tabacum

During the process of flue-curing and processing, leaves from cash crops such as tea and tobacco frequently undergo a phenomenon of browning, leading to reduced quality and significant economic losses. Despite a variety of approaches developed to suppress browning, little is known about the role that flue-curing of postharvest leaves with stems plays in delaying browning. This study investigated the impact of leaf-with-stem (LWS) flue-curing on the browning of tobacco and its underlying mechanisms. Physiological results indicated that LWS flue-curing effectively delayed browning by enhancing antioxidant capacity and maintaining reactive oxygen species (ROS) levels during the yellowing stage. Comprehensive transcriptome and metabolome analyses showed that LWS flue-curing significantly influenced various metabolic pathways. Specifically, 196, 218, and 402 metabolites, and 65, 131, and 718 genes exhibited significant changes at the 38 °C, 40 °C, and 42 °C stages, respectively, inhibiting membrane lipid degradation and enhancing the supply of reducing hydrogen through the oxidative pentose-phosphate pathway. Additionally, hormone signaling pathways were found to be associated with LWS flue-curing. These findings highlight the complex interplay of metabolic pathways and signaling networks in attenuating browning, providing valuable insights for minimizing postharvest leaf browning during flue-curing and processing.

MeJA enhances antioxidant activity and reduces membrane lipid degradation by maintaining energy charge levels in crystal grapes

Methyl jasmonate (MeJA) has shown promising applications in mitigating fruit quality deterioration. However, whether pre-harvest spraying of MeJA enhances post-harvest grape antioxidant enzyme activities and inhibits membrane lipid degradation by regulating energy metabolism has not been reported. In this study, the effect of 50 μmol L–1 MeJA treatment on energy metabolism was investigated in “crystal” grapes stored for 32 d. Its roles in the antioxidant properties and membrane lipids were also investigated. The results showed that MeJA treatment reduced the decay, weight loss, and browning index, inhibited the accumulation of soluble solids, improved the appearance of the fruit, and had a protective effect on crystal grapes. Compared with the fruit, MeJA-treated fruit stalks had higher adenosine triphosphate and adenosine diphosphate content and energy charge, as well as higher hydrogen ion ATPase, calcium ion ATPase, cytochrome C oxidase, and succinate dehydrogenase activities. During storage, MeJA stimulated glutathione production by activating dehydroascorbate reductase and monodehydroascorbate reductase activities, thereby maintaining total antioxidant capacity, free radical scavenging ability, ferrous reducing ability in the fruit. In addition, MeJA treatment inhibited the increase of phospholipase D, lipoxygenase, palmitic acid, and stearic acid; promoted the accumulation of phosphatidylcholine, linoleic acid, and arachidonic acid; and increased the unsaturated fatty acid/saturated fatty acid ratio. Therefore, MeJA maintained a higher energy charge level in grape stalks to varying degrees, slowed down the energy deficit, and inhibited oxidative stress and membrane lipid peroxidation processes in grapes, thereby reducing fruit deterioration and maintaining better fruit quality during storage.

Quantitative analyses of major enzyme activities in postharvest fruit

AbstractThe quantitative determination of major enzyme activities in postharvest fruit is a necessary biochemical experiment to investigate the physiological and metabolic mechanisms of fruit ripeness, senescence, and stress responses. However, it is necessary to choose appropriate methods to stably extract and determine target analytes from complex plant matrices due to the dynamic changes in enzyme activities of postharvest fruit during storage. Here, we outline sensitive and accurate methods for measuring fruit enzyme activities associated with key physiological processes including respiration, reactive oxygen species scavenging, membrane lipid degradation, energy synthesis, cell walls degradation, and disease resistance. This manuscript aims to provide guidance for future research in postharvest biology.

Enhancing shelf life of bell peppers through preharvest fertigation with calcium and potassium thiosulfate: A focus on antioxidant and cell wall degradation enzymes

In this study, the effectiveness of preharvest fertigation using calcium thiosulfate (CaTS) and potassium thiosulfate (KTS) to enhance the shelf life of bell peppers was investigated. The nutrient solution was enriched with KTS (either 0.26 or 0.53 mM of a commercial formulation) or CaTS (0.66 mM of a commercial formulation), and compared to a commercial source-based nutrient solution as a control. Fruit quality attributes and the activity of key enzymes involved in oxidative stress defense, enzymatic browning, cell wall degradation, and membrane lipid degradation were investigated for 30 days of storage. Results showed that CaTS and KTS treatments preserved protein (a secondary energy reserve) and proline content, and enhanced the fruit's PSII activity throughout storage. Despite increased phenylalanine ammonia-lyase activity, CaTS and KTS fertigation did not affect polyphenol oxidase activity. CaTS and KTS fertigation increased the activity of five (out of seven) antioxidant enzymes and impaired the activity of one (out of two) cell wall hydrolytic enzyme. CaTS was the most effective treatment, followed by KTS (0.53 mM), in causing these promotive effects. In conclusion, preharvest application of CaTS (0.66 mM) and KTS (0.53 mM) prolonged the postharvest life and delayed senescence of bell pepper fruits by preserving fruit weight, firmness, and photosynthetic performance, as well as enhancing the antioxidant defense system.

Metabolomics and transcriptomic profiles reveal membrane lipid metabolism being an important factor of sliced taro browning

Cut-surface browning poses a prominent concern when it comes to the storage and consumption of sliced taro. This study evaluated the browning development of sliced taro during cold storage and investigated the underlying browning mechanisms through metabolomics and transcriptomic analyses. Metabolomics analysis revealed a consistent increase in the abundance of metabolites, specifically linolenic acid and its derivatives, as well as hydroperoxides, during the aggravated browning process, suggesting the degradation of membrane lipids, as linolenic acid is a major structural composition of cell membranes. Transcriptomic analysis showed that differentially expressed genes having upregulated expression during the browning process were enriched in the α-Linolenic acid metabolism pathway. Weighted gene co-expression network analysis identified two highly correlated modules with taro slice browning during storage, and genes showing a positive correlation were also enriched in the α-Linolenic acid metabolism pathway. Taken together, these findings indicate that the degradation of membrane lipids during taro browning and the loss of membrane compartmentalization might be key factors contributing to sliced taro browning. Additionally, the upregulation of LOX genes and increased protein activity, along with elevated levels of MDA during browning development, further validate the correlation between membrane lipid peroxidation and taro browning. Overall, this study contributes to our knowledge of the browning mechanisms in fresh-cut foods, providing valuable insights for future research and potential strategies for mitigating browning in sliced taro under cold storage conditions.

Acidic electrolyzed-oxidizing water treatment mitigated the disease progression in Phomopsis longanae Chi-infected longans by modulating ROS and membrane lipid metabolism

Postharvest harmful pathogenic infestation leads to rapid decay in longan fruit. Compared with P. longanae-infected longans, AEOW alleviated fruit disease severity and diminished the O2-. production rate and MDA content. It also increased APX, CAT, and SOD activities, delayed the decrease in the levels of GSH and AsA, as well as the reducing power and DPPH radical scavenging ability, which resulted in a decline in membrane lipid peroxidation in P. longanae-infected longans. Additionally, AEOW reduced LOX, lipase, PI-PLC, PC-PLC, and PLD activities, maintained higher levels of PC, PI, IUFA, USFAs, and U/S, while reducing levels of PA, DAG, SFAs, and CMP. These effects alleviated membrane lipid degradation and peroxidation in P. longanae-infected longans. Consequently, AEOW effectively maintained membrane integrity via improving antioxidant capacity and suppressing membrane lipid peroxidation. This comprehensive coordination of ROS and membrane lipid metabolisms improved fruit resistance and delayed disease development in longans.

The Role of MaWRKY70 in Regulating Lipoxygenase Gene Transcription during Chilling Injury Development in Banana Fruit.

Banana is a typical cold-sensitive fruit; it is prone to chilling injury (CI), resulting in a quality deterioration and commodity reduction. However, the molecular mechanism underlying CI development is unclear. In this study, cold storage (7 °C for 5 days) was used to induce CI symptoms in bananas. As compared with the control storage (22 °C for 5 days), cold storage increased the CI index and cell membrane permeability. Moreover, we found that the expression levels of the WRKY transcription factor MaWRKY70 were increased consistently with the progression of CI development. A subcellular localization assay revealed that MaWRKY70 was localized in the nucleus. Transcriptional activation analyses showed that MaWRKY70 processed a transactivation ability. Further, an electrophoretic mobility shift assay (EMSA) and dual-luciferase reporter (DLR) assays showed that MaWRKY70 was directly bound to the W-box motifs in the promoters of four lipoxygenase (LOX) genes associated with membrane lipid degradation and activated their transcription. Collectively, these findings demonstrate that MaWRKY70 activates the transcription of MaLOXs, thereby acting as a possible positive modulator of postharvest CI development in banana fruit.

EjCML19 and EjWRKY7 synergistically function in calcium chloride-alleviated chilling injury of loquat fruit

The regulatory function of calcium chloride (CaCl2) in chilling injury (CI) has been proven in loquat fruit. Nevertheless, its physiological and molecular mechanisms are relatively still unclear. In this work, the CaCl2 treatment reduced the CI in loquat fruit, with a lower internal browning index, firmness, and higher extractable juice in comparison with the control. Moreover, CaCl2 application impacted the contents of phenolic acids in cold-stored loquat fruit. Transcriptome analysis identified a total of 5416 differently expressed genes (DEGs), and the key DEGs were enriched in many metabolic pathways, including phenylpropanoid biosynthesis, biosynthesis of secondary metabolites, plant hormone signal transduction, phenylalanine metabolism, membrane lipid degradation, starch and sucrose metabolism. The fold change and the expression intensity of EjCML19 and EjWRKY7 in loquat fruit during cold storage were higher, and EjCML19 could interact with EjWRKY7 in yeast cells. The qRT-PCR analysis found that CaCl2 induced the transcription of EjCML19 and EjWRKY7 but down-regulated browning-related genes EjRBOHC and EjPPO in loquat fruit. The genes (EjRBOHC and EjPPO) contain W-box elements in their promoters, implying that they might be target genes of EjWRKY7. Therefore, EjCML19 and EjWRKY7 were selected and cloned from loquat fruit to explore their regulatory role of EjRBOHC and EjPPO. Further investigation revealed that EjWRKY7 negatively modulated the expression of EjRBOHC and EjPPO by binding to their promoters. EjCML19 enhanced EjWRKY7-mediated transcriptional repression of EjPPO in loquat fruit under cold stress. Taken together, EjCML19 and EjWRKY7 synergistically regulated the transcription of browning-related genes, which functioned a positive role in CaCl2-alleviated chilling injury in loquat fruit under refrigeration.

Salicylic acid treatment delayed the browning development in the pericarp of fresh longan by regulating the metabolisms of ROS and membrane lipid

Longans is popular among consumers because of its rich nutritional value, but it is prone to pericarp browning as it is harvested in the high-temperature season. This work was to investigate the effects of salicylic acid (SA) on the metabolisms of reactive oxygen species (ROS) and membrane lipid and their relationship with pericarp browning of postharvest longans. ‘Fuyan’ longans were soaked in the solution of 0.3 g L-1 SA for 5 min, then stockpiled at 28 °C. The results showed that, the pericarp browning index in SA-treated fruit was 42% lower than that in the control fruit at day 5 of storage. Meanwhile, SA treatment reduced the damage severity of cell membrane structure, and maintained a low level of cell membrane permeability, which was 25% lower than that in the control fruit at day 5 of storage. Additionally, compared to the control fruit, SA-treated longans displayed higher levels of pericarp L*, flavonoid, chlorophyll, carotenoid, total phenolics, and anthocyanin, higher activities of pericarp superoxide dismutase, catalase, and ascorbate peroxidase, higher values of pericarp reducing power and 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging ability, and higher amounts of pericarp ascorbic acid and glutathione, but lower levels of pericarp ROS and malondialdehyde. Moreover, SA-treated samples exhibited lower activities of pericarp phospholipase, lipase, and lipoxygenase, lower levels of pericarp phosphatidic acid and saturated fatty acids (SFA), but higher values of pericarp phosphatidylcholine, phosphatidylinositol, and unsaturated fatty acids (USFA), higher index of USFA, and higher ratio of USFA to SFA. These findings corroborated that SA delayed-browning occurrence in the pericarp of fresh longans was because SA enhanced the capacity to remove ROS, and reduced ROS accumulation and the membrane lipid degradation, thus maintaining the cellular membrane structure, reducing the degradation of pigments, and allowing the fresh longans to maintain a better appearance. Consequently, SA could be an effective means for suppressing pericarp browning and improving the commercial value of fresh longans.

Effects of Organic Ligands on the Antibacterial Activity of Reduced Iron-Containing Clay Minerals: Higher Extracellular Hydroxyl Radical Production Yet Lower Bactericidal Activity.

Reduced iron-containing clay (RIC) minerals have been documented to exhibit antibacterial activity through a synergistic action of extracellular membrane attack and intracellular oxidation of cellular components. However, the relative importance between extracellular and intracellular processes has remained elusive. Here, metal-chelating organic ligands (lactate, oxalate, citrate, and ethylene diaminetetraacetic acid (EDTA)) were amended to the bactericidal assays such that the importance of the two processes could be evaluated. Reduced nontronite (rNAu-2) was used as a model clay mineral to produce extracellular hydroxyl radical (•OH) upon oxygenation. The presence of Fe-chelating ligands increased •OH yield by 3-5 times. Consequently, bacterial cell membrane attack was enhanced, yet the antibacterial activity of RIC diminished. Additional experiments revealed that the ligands inhibited soluble metal ions from adsorption onto the bacterial cell membrane and/or penetration into the cytoplasm. Consequently, intracellular Fe concentration for the ligand-treated group was nearly 2 orders of magnitude lower than that for no-ligand control, which greatly decreased intracellular accumulation of reactive oxygen species (ROS) and increased cell survival. These results highlight that destruction of intracellular contents (proteins and DNA) is more important than oxidative degradation of membrane lipids and cell envelope proteins in causing bacterial cell death by RIC.

Methylcyclopropene treatment retards the yellowing in pak choi (Brassica rapa subsp. Chinensis) through modulating the programmed cell death during storage at 20°C

The deterioration of post-harvest quality in plants has been shown to be connected with the occurrence of programmed cell death (PCD). Our previous research indicated that 5 μL L−1 1-Methylcyclopropene (1-MCP) delays the yellowing of post-harvest pak choi leaves. However, whether 1-MCP alleviates pak choi yellowing through regulating PCD process, and the regulatory mechanism of 1-MCP on PCD are still unclear. Results showed that 5 μL L−1 1-MCP could retard the PCD process of pak choi as proved by the maintenance of lower cytochrome C content and caspase-3 activity. The results of cell mortality and trypan blue staining further confirmed this view. Forty-five differentially expressed genes (DEGs) involving PCD of pak choi were identified in the transcriptome data. The treatment suppressed the over-accumulation of reactive oxygen species (ROS) (superoxide anion O2·− and hydrogen peroxide H2O2), lipid membrane oxidation, ethylene production, and expression of their related genes (BcRBOHC, BcRBOHD, BcLOX1/3/5, BcACO, BcACO4 and BcEIN3)) during senescence. This relationship was also connected to the preservation of higher level in antioxidant capacity of antioxidase and antioxidants (ascorbate-glutathione (AsA-GSH)), as well as high expression of their related genes (BcSOD, BcAPX, and BcGR) in 1-MCP-treated pak choi. Moreover, 1-MCP down-regulated the transcript of genes involved in PCD, regulated the expression of genes associated with mitochondrial membrane transport, respiration and signaling, and chloroplast membrane transport and REDOX, thereby contributing to the inhibition of PCD. The correlation analysis revealed that pak choi yellowing was positively related with the process of PCD. Taken together, the present study indicated that 1-MCP could delay the yellowing of pak choi through mitigating PCD process, involving the regulation of ROS metabolism, membrane lipid degradation, antioxidant status and ethylene production.

Non-thermal effects of microwave irradiation alleviates postharvest chilling injury of peach fruit by retarding phenolic accumulation and enhancing membrane stability

Postharvest chilling injury (CI) of fruit, including peaches, is a huge challenge to horticultural product preservation. Microwave irradiation can be used as a physiological regulator due to the thermal effects; however, its non-thermal effects on the CI of postharvest fruit remain unclear. Thus, the physiological attributes and metabolisms involving phenolics, fatty acids, and sugars were compared between ‘Zhongtao No.9’ peaches treated with microwave irradiation at 45.5 W for different durations and control. Microwave treatment especially at 45.5 W for 7 min without inducing thermal effects could significantly inhibit internal browning caused by CI, concomitant with reduced total phenolic content. Moreover, the maintenance of membrane stability was indicated by a boosted double bond index, which may be attributed to the inhibition of membrane lipid degradation, and sucrose accumulation. In summary, the non-thermal effects of microwave irradiation contribute to CI alleviation through restraining phenolic content and maintaining membrane stability in peach fruit.

The stability of cell structure and antioxidant enzymes are essential for fresh-cut potato browning

In this study, the browning degrees of fresh-cut potatoes of different cultivars were investigated. Fresh-cut potatoes of the ‘Huangjin’ cultivar exhibited a higher browning index and sensory quality deterioration over time compared with ‘Minshu’ potatoes. ‘Huangjin’ exhibited a higher activity of browning-related enzymes such as polyphenol oxidase, tyrosinase, peroxidase, phenylalanine ammonia-lyase, phospholipase D (PLD), and lipoxygenase (LOX) than ‘Minshu’. Furthermore, ‘Minshu’ exhibited lower H2O2 and malonaldehyde (MDA) contents, lower membrane lipid degradation and peroxidation, and delayed browning, attributable to its low PLD and LOX activities. The ultrastructure of ‘Minshu’ cells remained intact 7 h after cutting, while that of ‘Huangjin’ cells was severely damaged, and ‘Minshu’ cells exhibited more Golgi complexes and black particles than ‘Huangjin’ cells. Moreover, ‘Huangjin’ cells exhibited numerous multivesicular bodies, which were nonexistent in ‘Minshu’ cells. The results show that ‘Minshu’ potatoes feature a lower browning-related enzyme activity than ‘Huangjin’, and a tough cell structure to resist post-cut browning.

Exogenous melatonin ameliorates yellowing of postharvest pak choi (Brassica rapa subsp. chinensis) by modulating chlorophyll catabolism and antioxidant system during storage at 20 °C

The objective of this study was to investigate the regulatory mechanism of melatonin (MT) treatment on leaf yellowing of pak choi during storage at 20 °C. Results showed that 500 μmoL L−1 MT alleviated the yellowing process of pak choi as proved by the maintenance of high level of leaf colour, chlorophyll content and chlorophyll fluorescence parameters (Fo, Fm and Fv/Fm), and the market life of pak choi was extended by 2 d compared to the control. The weight loss and respiration rate were effectively alleviated by MT treatment. MT treatment restrained chlorophyll breakdown by down-regulating the activity of chlorophyll-degrading enzymes (chlorophyllase CLH, pheophytinase PPH and Mg-dechelatase MDS) and expression of their related genes (BcCLH, BcPPH1/2, BcSGR, BcHCAR, BcNYC1 and BcCAO). Meanwhile, MT suppressed the over-accumulation of reactive oxygen species (ROS) (superoxide anion O2·− and hydrogen peroxide H2O2), and lipid membrane oxidation and associated gene (BcLOX) expression during senescence, thus helping to keep green colour of pak choi. This relationship was also connected to the maintenance of higher level in antioxidant ability of antioxidase (superoxide dismutase SOD, ascorbate peroxidase APX, peroxidase POD and catalase CAT) and antioxidants (ascorbate-glutathione (AsA-GSH)), as well as high expression of their related genes (BcSOD, BcPOD, BcCAT, BcGPX and BcAPX) in pak choi treated with MT. In conclusion, these findings suggested that MT could delay the yellowing of pak choi, involving the regulation of chlorophyll metabolism, ROS metabolism, membrane lipid degradation, and antioxidant capacity. The results provide a possible target for delaying the yellowing of green vegetables.

CaCl2 mitigates chilling injury in loquat fruit via the CAMTA5-mediated transcriptional repression of membrane lipid degradation genes

Loquat fruit is vulnerable to chilling injury (CI) under long-term low temperature storage. The application of calciumchloride (CaCl2) can alleviate CI in loquat fruit, however, the molecular mechanisms remain unclear. In this study, the loquat fruit were immersed in 1 % CaCl2 solution for 10 min and then stored at 1 ± 1 ℃ for 35 d. The results showed that CaCl2 treatment suppressed the increases in internal browning index, electrolyte leakage, and malonaldehyde content in loquat fruit under chilling stress. The internal browning index in CaCl2-treated loquat fruit was 33.34 % lower than that in the control at the end of storage. Meanwhile, CaCl2 treatment delayed the phospholipids degradation, and retained high level of unsaturated/saturated fatty acid ratio, which was 15.21 % higher than that in the control fruit at the end of storage. The CaCl2 treatment also decreased the enzymatic activities and gene expressions of phospholipase D (PLD), phospholipase C (PLC), and lipoxygenase (LOX) in loquat fruit during cold storage. Moreover, a calmodulin-binding transcription activator (CAMTA) transcription factor (TF), EjCAMTA5, was cloned from loquat fruit. The EjCAMTA5 expression was up-regulated by cold stress and CaCl2 treatment. Further investigation revealed that EjCAMTA5 directly bound to the promoters of EjPLC6-like and EjLOX5 to repress their transcription. Taken together, these findings implied that CaCl2 application could activate the EjCAMTA5-mediated transcriptional repression of EjPLC6-like and EjLOX5 genes, which contributed to delaying the degradation of membrane lipid and maintaining the integrity of cell membrane, thereby inhibiting the occurrence of browning in loquat fruit under chilling stress.

Effect of Drought Stress on Degradation and Remodeling of Membrane Lipids in Nostoc flagelliforme.

Nostoc flagelliforme is a kind of terrestrial edible cyanobacteria with important ecological and economic value which has developed special mechanisms to adapt to drought conditions. However, the specific mechanism of lipidome changes in drought tolerance of N. flagelliforme has not been well understood. In this study, the ultra-high-performance liquid chromatography and mass spectrometry were employed to analyze the lipidome changes of N. flagelliforme under dehydration. A total of 853 lipid molecules were identified, of which 171 were significantly different from that of the control group. The digalactosyldiacylglycerol/monogalactosyldiacylglycerol (DGDG/MGDG) ratio was increased. The amount of wax ester (WE) was sharply decreased during drought stress, while Co (Q10) was accumulated. The levels of odd chain fatty acids (OCFAs) were increased under dehydration, positively responding to drought stress according to the energy metabolism state. In conclusion, the lipidomic data corroborated that oxidation, degradation, and biosynthesis of membrane lipids took place during lipid metabolism, which can respond to drought stress through the transformation of energy and substances. Besides, we constructed a lipid metabolic model demonstrating the regulatory mechanism of drought stress in N. flagelliforme. The present study provides insight into the defense strategies of cyanobacteria in lipid metabolic pathways.

Links between autophagy and lipid droplet dynamics.

Autophagy is a catabolic process in which cytoplasmic components are delivered to vacuoles or lysosomes for degradation and nutrient recycling. Autophagy-mediated degradation of membrane lipids provides a source of fatty acids for the synthesis of energy-rich, storage lipid esters such as triacylglycerol (TAG). In eukaryotes, storage lipids are packaged into dynamic subcellular organelles, lipid droplets. In times of energy scarcity, lipid droplets can be degraded via autophagy in a process termed lipophagy to release fatty acids for energy production via fatty acid β-oxidation. On the other hand, emerging evidence suggests that lipid droplets are required for the efficient execution of autophagic processes. Here, we review recent advances in our understanding of metabolic interactions between autophagy and TAG storage, and discuss mechanisms of lipophagy. Free fatty acids are cytotoxic due to their detergent-like properties and their incorporation into lipid intermediates that are toxic at high levels. Thus, we also discuss how cells manage lipotoxic stresses during autophagy-mediated mobilization of fatty acids from lipid droplets and organellar membranes for energy generation.

Integrated proteome and lipidome analysis of naturally aged safflower seeds varying in vitality.

Seed ageing has an important effect on germination and productivity. During natural ageing, seed vigour decreases rapidly but, to date, the molecular mechanisms underlying this decrease have not been fully elucidated. Using omics, some of the details regarding seed vigour decline during natural ageing might be elucidated through integrated analysis. Safflower seed germination and physio-biochemical changes during natural ageing (stored for 4, 16 and 28 months) were determined. Proteome and lipidome profiling during natural seed ageing was performed, and the differentially expressed proteins and lipid metabolite species analysed. The surface and internal structures of cotyledons were observed. An integrating analysis of the proteome and lipidome was also carried out. Natural seed ageing significantly decreased safflower seed germination and vigour. 4,184 proteins and 1,193 lipids were quantified, both of which show huge differences among the different naturally aged seeds. The surface of the cotyledons collapsed and cracked, and the oil bodies become looser during natural ageing. The total content of DAG and PA increased, while the content of TAG and PL (PC, PE, PS, PI and PL) significantly decreased during seeds ageing. Two lipase genes (HH-026818-RA and HH-025320) likely participated in this degradation of lipids. We conclude that the enzymes that participate in glycerolipid metabolism and fatty acid degradation probably lead to the degradation of oil bodies (TAG) and membrane lipids (PC, PE, PS, PI, PG) and, ultimately, destroy the structure, causing a decline in seed vigour during natural seed ageing.