Changes In Fatty Acid Composition Research Articles

Multiple caleosins have overlapping functions in oil accumulation and embryo development.

Caleosins are lipid droplet- and endoplasmic reticulum-associated proteins. To investigate their functions in oil accumulation, expression levels of caleosins in developing seeds of Arabidopsis thaliana were examined and four seed-expressed caleosins (CLO1, CLO2, CLO4, and CLO6) were identified. The four single mutants showed similar minor changes of fatty acid composition in seeds. Two double mutants (clo1 clo2 and clo1×clo2) demonstrated distinct changes of fatty acid composition, a 16-23% decrease of oil content, and a 10-13% decrease of seed weight. Moreover, a 40% decrease of oil content, further fatty acid changes, and misshapen membranes of smaller lipid droplets were found in seeds of quadruple CLO RNAi lines. Notably, ~40% of quadruple CLO RNAi T1 seeds failed to germinate, and deformed embryos and seedlings were also observed. Complementation experiments showed that CLO1 rescued the phenotype of clo1 clo2. Overexpression of CLO1 in seedlings and BY2 cells increased triacylglycerol content up to 73.6%. Transcriptome analysis of clo1 clo2 developing seeds showed that expression levels of some genes related to lipid, embryo development, calcium signaling, and stress responses were affected. Together, these results suggest that the major seed-expressed caleosins have overlapping functions in oil accumulation and show pleiotropic effects on embryo development.

Laktasyonun İlk 30 Gününde Koyun ve Keçi Sütündeki Yağ Asidi Profili ile Bazı Sağlık İndekslerinin Karşılaştırılması

Fatty acid composition in milk has a vital importance in the early lactation period when lambs are milking. In this study, the change in milk fatty acid composition of Akkaraman ewe and Hair goats fed under the same conditions in the first 30 days of lactation was investigated. 10 Akkaraman ewe and 10 Hair goats were used in 2-5 parities. Ewe and goats were born in February. The animals were kept to the same feeding indoor, while experiment was going on. In addition to 1 kg of barley per animal, wheat straw was given ad libitum. Individual milk samples were taken from each animal on 0th, 1st, 3rd, 7th, 15th and 30th of lactation days. While C16:1, C18:3n3 were found more in goat milk (p

Stability and Change in Fatty Acids Composition of Soybean, Corn, and Sunflower Oils during the Heating Process

This work has been undertaken to investigate the effect of heat treatment on the edible oils (soybean, sunflower, and corn) used in frying and cooking, in particular on the fatty acid composition. The heating process was maintained at 150, 180, 210, and 240°C. At each temperature, the variation of the fatty acid composition was determined after 12, 24, 36, 48, and 60 h of treatment by using an improved analytical gas chromatography method. This study showed that the oils, which had undergone a temperature of 150 to 180°C, kept some thermal stability and preserved their fatty acid composition at different treatment periods. At the temperature (180°C), two new fatty acids (C8:0 and C12:0) appeared, which could be explained by the transformation of the other fatty acids during the heating process by different chemical reactions. However, the composition of the three oils was significantly affected at 210°C and 240°C. Two trans-fatty acids (C18:1 9t and C18:2tt) were generated proportionally to heat treatment during the heating process for the three oils, providing information on their oxidative state. The results showed that sunflower oil was most affected by the heating temperature than soybean and corn oil. Therefore, more attention should be paid to the heat treatment used and the heating period to preserve the quality of edible oils.

Insight into the effect of frozen storage on the changes in volatile aldehydes and alcohols of marinated roasted beef meat: Potential mechanisms of their formation

This study aimed to evaluate the effect of frozen storage on the changes in volatile aldehydes (VAs), volatile alcohols (VCs), lipid oxidation, and fatty acid composition of marinated roasted beef meat. Thirty VAs and VCs were identified in all meat samples by using headspace solid-phase microextraction-gas chromatography-mass spectrometry. The total concentrations of VAs increased with storage periods up to four months and gradually decreased. Whereas the total concentrations of VCs decreased with prolonged storage periods. The contents of thiobarbituric acid reactive substances and hexanal increased with prolonged storage periods in all samples until four months and then gradually decreased except the hexanal contents in the control sample (BS1), which showed an increase up to six months. Saturated and monounsaturated fatty acids decreased after storage in all samples except the control. By contrast, polyunsaturated fatty acids increased with prolonged storage in all samples. The correlation analysis showed the positive correlation of flavor compounds with fatty acids, E-nose, and sensory notes.

Dietary plant oil supplemented with arachidonic acid and eicosapentaenoic acid affects the fatty acid composition and eicosanoid metabolism of Atlantic salmon (Salmo salar L.) during smoltification

This study sought to investigate whether a “natural diet” (mimicking the fatty acid composition of freshwater aquatic insects eaten by salmon parr) during the freshwater (FW) life stage of pre-smolt Atlantic salmon (Salmo salar L.) affected red blood cells and gill fatty acid composition as well as eicosanoid metabolism in gill during smolting at different temperatures. Before being transferred to seawater (SW), salmon parr were fed with a modified (MO) diet containing vegetable oils (rapeseed, palm, and linseed oils) supplemented with eicosapentaenoic acid (EPA) and arachidonic acid (ARA) to completely replace the fish oil (FO). Fatty acid composition in red blood cells and gill tissues was determined before SW transfer and six weeks after. Additionally, the expression of genes associated with eicosanoid metabolism and Na+/K+-ATPase (NKA) activity in salmon gill was examined at different temperatures before SW transfer and 24 h after. The results showed the changes in fatty acid composition, including sum monounsaturated fatty acids (MUFAs), docosahexaenoic acid (DHA), ARA, EPA, and sum n-6 polyunsaturated fatty acids (n-6 PUFA) in both red blood cells and gill tissues at the FW stage were consistent with the fatty acid profiles of the supplied MO and FO fish diets; however sum EPA and DHA composition exhibited opposite trends to those of the FO diet. The proportion of ARA, EPA, and n-6 PUFA increased, whereas sum MUFAs and DHA decreased in the red blood cells and gill tissues of MO-fed fish compared to those fed with the FO diet at FW stage. Additionally, 5-lipoxygenase-activating protein (Flap) expression was downregulated in MO-fed fish prior to SW transfer. During the process of SW transfer at different temperatures, the MO diet remarkably suppressed NKAα1a expression in MO-fed fish both at 12 and 16 °C. The MO diet also upregulated phospholipase A2 group IV (PLA2g4) expression in gills at 8, 12, and 16 °C, but suppressed phospholipase A2 group VI (PLA2g6) expression in gills at 12 °C compared to FO-fed fish at 12 °C and MO-fed fish at 8 °C. The MO diet also upregulated Cyclooxygenase 2 (Cox-2) expression at 8 °C compared to FO-fed fish and increased Arachidonate 5-lipoxygenase (5-Lox) expression in MO-fed fish at 16 °C compared to both FO-fed fish at 16 °C and MO-fed fish at 8 °C. Our study also determined that both SW transfer water temperatures and diets during the FW period jointly influenced the mRNA expression of PLA2g4, PLA2g6, and Lpl, whereas 5-Lox was more sensitive to dietary changes. In conclusion, the MO diet affected the fatty acid composition in gill and in red blood cells. When transferred to SW, dietary ARA supplementation could promote the bioavailability for eicosanoid synthesis in gill mainly via PLA2g4 activation, and potentially inhibit the stress and inflammatory response caused by different water temperatures through dietary EPA supplementation.

Critical assessment of metabolism and related growth and quality traits in trout fed spirulina-supplemented plant-based diets

Nowadays in aquaculture, the nutrition of carnivorous fish species requires the development of sustainable plant-based diets. Supplementation with microorganisms such as spirulina could offer an alternative to full plant-based diets that are inappropriate for carnivorous species such as rainbow trout. However, the benefits and drawbacks of spirulina supplementation on fish performance and metabolism need to be assessed to substantiate spirulina as an appropriate ingredient. The objective of this work was to determine the metabolic utilization of a plant-based diet supplemented with two levels of spirulina (5% and 15%) and to compare it to a full plant-based (PB) and a commercial-like (COM) diet for trout. Spirulina supplementation induced both a decrease in feed intake and an increase in feed efficiency while maintaining growth and a putative reorientation of lipid deposition from viscera to muscle. Fatty acid changes, including an increase in saturated fatty acids, a decrease in monounsaturated fatty acids, and color changes with an increase in b* index (yellow), suggested a slight alteration of the nutritional and visual quality of fish fed a spirulina diet. 1H NMR metabolomics profiling was used to measure metabolites in experimental feeds and in fish plasma, liver, and muscle. Two specific compounds of the spirulina ingredient were identified and determined to have opposed metabolic fates: i) a quinone-like compound was found to accumulate in liver and ii) β-hydroxybutyrate was found to be completely metabolized. The main metabolites modulated by spirulina in plasma and tissues were involved in energy and amino acid metabolisms. Spirulina supplementation almost suppressed the accumulation of glucose and essential amino acids in fish plasma and muscle induced by the PB diet. However, these compounds, as well as betaine, were found to accumulate in the liver of fish fed spirulina-supplemented diets. An alteration of liver metabolism due to the specific fatty acid profile and quinone-like compound of spirulina is suspected. A correlative approach of fish performance, quality traits, and metabolomic data in plasma and liver suggests that the maintenance of growth rate and feed efficiency using spirulina supplementation of a PB diet requires not only the supply of a well-balanced protein but also the redirection of lipid metabolism. However, observed changes in fatty acid composition and color suggest further alterations of the phospholipid metabolism. This work thus provides a contrasted fate of spirulina supplementation of a PB diet with both expected positive effects and unexpected negative effects that must be investigated further.

Milk Fat Depression and Trans-11 to Trans-10 C18:1 Shift in Milk of Two Cattle Farming Systems

Milk fat depression (MFD) syndrome, a consistent decrease in milk fat content, is related to important changes in fatty acid composition due to feed imbalances and the consequent ruminal metabolism alteration. Milk produced in two different farming systems was compared: Holstein Friesian fed with unified in intensive production and Podolica raised on a pasture in an extensive system. Milk chemical characteristics and fatty acid composition were determined comparing milk with a normal fat level (>3.8%) to milk with a low fat level (<3.2%) in each breeding system. Holstein Friesian milk showed the decrease in trans-11 and increase in trans-10 C18:1 (shift from trans-11 to trans-10 C18:1) in low fat with respect to normal fat milk with a consequent decrease in the trans-11/trans-10 C18:1 ratio. Even conjugated linoleic acid (CLA), C18:2 cis-9, trans-11, was lower while CLA trans-10, cis-12 was higher in low fat milk than in normal fat milk from Holstein Friesian. These changes, that are indicators of MFD syndrome, were not found in Podolica milk between fat levels. Holstein Friesian milk showed less short-chain fatty acids (9.48 % vs. 11.05%, p < 0.001), trans vaccenic acid (C18:1 trans-11, 0.51% vs. 3.39%, p < 0.001), rumenic acid (CLA C18:2 cis-9, trans-11, 0.32% vs. 1.45%, p < 0.001) and total CLA (0.53% vs. 1.91%, p < 0.001) contents than Podolica milk. Further losses of these human healthy nutrients in low fat Friesian milk reduced the nutritional quality of the milk, while the milk from animals raised on the pasture was of better quality even when the level of fat was low.

Effects of Repeated Heating on Fatty Acid Composition of Plant-Based Cooking Oils.

Several polyunsaturated fatty acids are considered to have beneficial health effects, while saturated fatty acids and industrial trans fatty acids (TFAs) are linked to negative health consequences. Given the increased formation of TFAs during heating, many studies already investigated compositional changes in oils after prolonged heating or at extremely high temperatures. In contrast, our aim was to measure changes in fatty acid composition and in some health-related indices in edible oils after short-time heating that resembles the conventional household use. Potatoes were fried in palm, rapeseed, soybean, sunflower and extra virgin olive oils at 180 °C for 5 min, and samples were collected from fresh oils and after 1, 5 and 10 consecutive heating sequences. Regardless of the type of oil, the highest linoleic acid and alpha-linolenic acid values were measured in the fresh samples, whereas significantly lower values were detected in almost all samples following the heating sequences. In contrast, the lowest levels of TFAs were detected in the fresh oils, while their values significantly increased in almost all samples during heating. Indices of atherogenicity and thrombogenicity were also significantly higher in these oils after heating. The present data indicate that prolonged or repeated heating of vegetable oils should be avoided; however, the type of oil has a greater effect on the changes of health-related indices than the number of heating sequences.

Repeated restraint stress modifies fatty acid and amino acid metabolism in the mouse skin.

In modern society, stress caused by relationships and emotions is one of the greatest social problems. Similar to humans, domestic and captive animals live under various stresses. Several stresses have been associated with skin disorders, such as atopic dermatitis, but there is a lack of reliable and objective indicators for the characterization of this association. This study aimed to define the changes in fatty acid composition and amino acid concentration in the skin following repeated restraint stress in ICR mice. Mice subjected to 30 min of daily restraint stress for 8 days showed changes in the composition of saturated fatty acids, such as an increase in palmitic acid content, which are the substrates of Δ-9 desaturase. Conversely, unsaturated fatty acids decreased with stress treatment, which appeared to be a result of these fatty acids being the substrate of Δ-6 desaturase. Changes in fatty acid composition after stress treatment may be one of the factors that cause skin inflammation. The water-retention capacity may have been lowered by stress treatment because histidine and leucine, which are natural moisturizing factors, were significantly decreased. The collagen content in the skin gradually decreased after repeated stress treatment. Our results indicate that repeated restraint stress may impact skin health through changes in both the fatty acid composition and amino acid concentration in mice.

Comparative analysis of nutritional composition of seeds of wild-type soybean and lines overexpressing GmWRI1a

Context With the widespread use of transgenic soybeans (Glycine max (L. ) Merr.), their nutritional assessment for human food and animal feed is an important aspect of safety evaluation. WRINKLED 1 (WRI1) is a transcriptional activator of genes involved in fatty acid synthesis. Aims We aimed to evaluate the effect of overexpression of GmWRI1a in soybean on the nutritional profile of soybean seeds. Methods Using molecular biology techniques, we identified three transgenic soybean lines stably overexpressing GmWRI1a (GmWRI1a-OE). We quantified the nutritional and anti-nutritional components in seeds of GmWRI1a-OE and wild-type (DN50) soybean, and compared them on the basis of the principle of substantial equivalence. Key results The GmWRI1a and Bar genes were stably inherited in the three GmWRI1a-OE lines, and GmWRI1a protein content was higher in transgenic soybean seeds than in wild-type seeds. Overexpression of GmWRI1a resulted in changes in fatty acid composition, a significant increase in oil content, and a significant decrease in stachyose content in seeds. Contents of other nutritional components (proximates, amino acids and isoflavones) and anti-nutritional factors (phytic acid, trypsin inhibitors and raffinose) in seeds were not significantly different between the wild-type and GmWRI1a-OE lines. Conclusions Contents of nutritional and anti-nutritional components of GmWRI1a-OE seeds were all within the reference ranges reported for commercially available soybeans and, therefore, are substantially equivalent to those of wild-type seeds. Implications GmWRI1a-OE soybean seeds are a high-quality product for health-conscious consumers.

Comparative Assessment of Toxicity in Brassica Juncea L. And Changes in Fatty Acid Composition of Oil When Grown Under Two Regimes of Simulated F- Contamination

Comparative Assessment of Toxicity in Brassica Juncea L. And Changes in Fatty Acid Composition of Oil When Grown Under Two Regimes of Simulated F- Contamination

Enhancement of physicochemical characteristics of palm olein and winged bean (Psophocarpus tetragonolobus) seed oil blends

Incorporation of oils from non-conventional sources into palm olein through the blending process generates a sustainable source of novel oleins with improved physicochemical and functional properties. The objective of this study was to evaluate the effects of blending winged bean (Psophocarpus tetragonolobus) seed oil (WBSO) and palm olein (POo) on the physicochemical properties of the blends. Blends of WBSO (25, 50 and 75% w/w) with POo were prepared and changes in fatty acid (FA) and triacylglycerol (TAG) compositions, iodine value (IV), cloud point and thermal behaviour were studied. Reductions in palmitic (C16:0) and oleic (C18:1) acids with concomitant increases in linoleic (C18:2) and behenic (C22:0) acids were observed as the amount of WBSO increased in the blends. Blending WBSO and POo at 75:25 increased the unsaturated FA content from 56% in palm olein to 64% in the blend, producing the highest IV of 70.5 g I2/100g. At higher WBSO ratios, triunsaturated and diunsaturated TAG species within the blends increased while disaturated TAG species decreased. The lowest cloud point (8.8 °C) was obtained in the oil blend containing 50% WBSO, while the cloud point further increased with increasing amount of WBSO in the blends. This was possibly attributed to increased trisaturated TAG with very long-chained saturated FA (C20 to C24) inherently present in WBSO within the blends. Thermal behaviour analysis by differential scanning calorimetry of the oil blends showed higher onset temperatures for crystallisation with increasing proportions of WBSO in POo, with melting thermograms correspondingly showing decreasing onset melting temperatures. These findings showed that blending WBSO with POo enhanced the physicochemical characteristics of the final oil blends, resulting in higher unsaturation levels and improved cloudiness resistance.

Effect of Industrial Refining Process on Fatty Acid, Sterol, Volatile Compound Profile and 3-MCPD Ester Content of Canola and Corn Oils

The study reports the changes in fatty acid and sterol composition; as well as volatile and 3-MCPD ester content of two commercial vegetable oils at different steps of refining process. Canola and corn oils were collected from neutralization, bleaching, winterization and deodorization stages of a chemical refining plant and oil samples were evaluated for fatty acid, sterol, volatile compounds and 3-MCPD ester contents. Results have shown that total sterol contents decreased throughout the process by 15.22% and 42.57% for canola and corn oils, respectively. Total volatiles of canola oil decreased gradually during refining, however corn oil had significant increases at bleaching step. 3-MCPD ester contents were between 0.19-0.26 mg kg-1 for corn and 0.20-0.48 mg kg-1 for canola oils. Deodorization was found to be the most influential refining stage for formation of 3-MCPD esters.

Basal resources of river food webs largely affect the fatty acid composition of freshwater fish

1.Overfishing, altered flow regimes, loss of connectivity, pollution and other direct human disturbances have had a significant impact on freshwater fish biodiversity. While direct effects of these disturbances are well documented, some can also lead to changes in the nutritional composition at the base of freshwater food webs and may affect fish growth and reproduction. Thus far, little is known about how changes in the nutritional composition at the base of freshwater food webs are reflected in fish production and fatty acid composition.2.We conducted a field study in subalpine rivers in Austria to examine how variations in the food quality of basal food sources affect the biochemical composition of freshwater fish. Basal food sources (terrestrial leaves and periphyton), the abundant fish taxa brown trout (Salmo trutta) and European bullhead (Cottus gobio) and their macroinvertebrate prey were collected and their stable carbon isotopes (δ13C) and fatty acid (FA) compositions were measured.3.Our results show that periphyton was the major source of dietary carbon for fish and most invertebrates, except shredders, and a high-quality food for all consumers that provides long-chain polyunsaturated FA (LC-PUFA). In contrast, submerged leaves contained very low content of LC-PUFA and were low-quality food for consumers.4.Changes in periphyton FA across these river ecosystems were tracked in macroinvertebrate FA profiles and in the FA composition of muscle tissues in both fish species. In contrast, the FA composition of fish brain remained unaltered across the study streams.5.The docosahexaenoic acid (DHA, 22:6ω3) content in muscle tissues of S. trutta remained stable and did not correspond to changes of periphyton FA, indicating strong regulation of DHA in this species which is independent of aquatic food sources. In contrast, muscle DHA and eicosapentaenoic acid (EPA, 20:5ω3) content of C. gobio significantly declined when periphyton quality decreased, reflecting the strong impact of the nutritional quality of periphyton on the FA composition of this bottom-dwelling fish.6.Reduced nutritional quality of periphyton led to reduced LC-PUFA in muscle tissues of bottom-dwelling bullhead and even piscivorous brown trout, suggesting that changes of FA composition at the base of river food webs cannot be compensated by intermediate consumers, such as benthic invertebrates, that also convey dietary FA to fishes. This study highlights how subtle human disturbance to streams can affect freshwater fish species through changes to the nutritional quality of their basal food sources.

Changes in fatty acid composition of fatty fractions of dry‐cured beef during different drying temperature and chilled storage

Dry-cured beef is a traditional meat product of the Kazakh nomads in the Xinjiang Uygur Autonomous Region in northwestern China. In order to determine the effect of high temperature and short time drying on the fatty fractions of dry-cured beef. The beef of Xinjiang was used as the raw material and dried beef was dried at different drying temperatures. After being cooled down to room temperature, the meat samples were stored in a refrigerator at 4℃. Sampling occurred on days 0, 15, 30, and 60 for analysis of changes in pH, Water activities (aw), thiobarbituric acid reaction substrate (TBARS) value, and the lipid content and fatty acid composition of total intramuscular lipids, phospholipids, triglycerides, and free fatty acids (FAAs). The results showed that with prolonged storage time, the pH value increased slightly but this increase was not significant (p > .05). The aw value decreased slightly but this decrease was not significant (p > .05). The TBARS values increased by the greatest amount during treatment at 60°C from 0–60 days. After 60 days at 4°C, the TBARS values of the samples had increased from 0.237 to 0.813. The preferential hydrolysis of polyunsaturated fatty acids (PUFA) in the phospholipids was observed, and this resulted in the percentage of PUFA in the phospholipids decreasing markedly and the free fatty acids increasing significantly during storage. Therefore, there is a dynamic relationship between the fat content and the fatty acid composition, the phospholipids, and the free fatty acids during the storage of dry-cured beef treated at different temperatures. Practical applications The fat content and fatty acid composition are among the most valuable quality characteristics for Kazakh dry-cured beef. Understanding of the effects of lipid oxidation on the development of flavor will allow producers to control the flavor qualities of this product. This study is of great practical importance in the industrial development of traditional dry-cured beef.

The Impact of Medium Chain and Polyunsaturated ω-3-Fatty Acids on Amyloid-β Deposition, Oxidative Stress and Metabolic Dysfunction Associated with Alzheimer's Disease.

Alzheimer’s disease (AD), the most common cause of dementia in the elderly population, is closely linked to a dysregulated cerebral lipid homeostasis and particular changes in brain fatty acid (FA) composition. The abnormal extracellular accumulation and deposition of the peptide amyloid-β (Aβ) is considered as an early toxic event in AD pathogenesis, which initiates a series of events leading to neuronal dysfunction and death. These include the induction of neuroinflammation and oxidative stress, the disruption of calcium homeostasis and membrane integrity, an impairment of cerebral energy metabolism, as well as synaptic and mitochondrial dysfunction. Dietary medium chain fatty acids (MCFAs) and polyunsaturated ω-3-fatty acids (ω-3-PUFAs) seem to be valuable for disease modification. Both classes of FAs have neuronal health-promoting and cognition-enhancing properties and might be of benefit for patients suffering from mild cognitive impairment (MCI) and AD. This review summarizes the current knowledge about the molecular mechanisms by which MCFAs and ω-3-PUFAs reduce the cerebral Aβ deposition, improve brain energy metabolism, and lessen oxidative stress levels.

Fatty acid composition and cpDNA content in Arabidopsis thaliana mutants deprived of EGY1 protease

EGY1 (ethylene-dependent gravitropism-deficient and yellow-green 1) is an intramembrane metalloprotease located in chloroplasts, involved in many diverse processes including chloroplast development, chlorophyll biosynthesis, and the ethylene-dependent gravitropic response. Plants deprived of this protease display pleiotropic effects such as the yellow-green early senescence phenotype and a poorly developed thylakoid system membrane in the mature chloroplasts. We applied the GC/MS technique to analyze the changes in fatty acid composition in two egy1 mutant lines. We used DAPI staining and transmission electron microscopy methods to establish the number of nucleoids and the amount of chloroplast DNA. Our results indicated that the lack of EGY1 protease led to a dramatic overaccumulation and a dramatic decrease in the content of linolenic acid C18:3 and hexadecatrienoic acid C16:3, respectively. The amount of chloroplast DNA and the number of nucleoids were severely reduced in egy1 mutant lines. Similarly, a reduced correlation between DAPI and autofluorescence signal was observed, which may indicate some perturbations in nucleoid anchoring.

Homeophasic Adaptation in Response to UVA Radiation in Pseudomonas aeruginosa: Changes of Membrane Fatty Acid Composition and Induction of desA and desB Expression.

In bacteria, exposure to changes in environmental conditions can alter membrane fluidity, thereby affecting its essential functions in cell physiology. To adapt to these changes, bacteria maintain appropriate fluidity by varying the composition of the fatty acids of membrane phospholipids, a phenomenon known as homeophasic adaptation. In Pseudomonas aeruginosa, this response is achieved mainly by two mechanisms of fatty acid desaturation: the FabA-FabB and DesA-DesB systems. This study analyzed the effect of ultraviolet-A (UVA) radiation-the major fraction of solar UV radiation reaching the Earth's surface-on the homeophasic process. The prototypical strain PAO1 was grown under sublethal UVA doses or in the dark, and the profiles of membrane fatty acids were compared at early logarithmic, logarithmic and stationary growth phases. In the logarithmic growth phase, it was observed that growth under sublethal UVA doses induced the expression of the desaturase-encoding genes desA and desB and increased the proportion of unsaturated fatty acids; in addition, membrane fluidity could also increase, as suggested by the indices used as indicators of this parameter. The opposite effect was observed in the stationary growth phase. These results demonstrate the relevant role of UVA on the homeophasic response at transcriptional level.

Assessment on the oil accumulation by knockdown of triacylglycerol lipase in the oleaginous diatom Fistulifera solaris

Microalgae are promising producers of biofuel due to higher accumulation of triacylglycerol (TAG). However, further improvement of the lipid metabolism is critical for feasible application of microalgae in industrial production of biofuel. Suppression of lipid degradation pathways is a promising way to remarkably increase the lipid production in model diatoms. In this study, we established an antisense-based knockdown (KD) technique in the marine oleaginous diatom, Fistulifera solaris. This species has a capability to accumulate high content of lipids. Tgl1 KD showed positive impact on cell growth and lipid accumulation in conventional culture in f/2 medium, resulting in higher oil contents compared to wild type strain. However, these impacts of Tgl1 KD were slight when the cells were subjected to the two-stage growth system. The Tgl1 KD resulted in slight change of fatty acid composition; increasing in C14:0, C16:0 and C16:1, and decreasing in C20:5. This study indicates that, although Tgl1 played a certain role in lipid degradation in F. solaris, suppression of only a single type of TAG lipase was not significantly effective to improve the lipid production. Comprehensive understanding of the lipid catabolism in this microalga is essential to further improve the lipid production.

Phenotypic convergence in a natural Daphnia population acclimated to low temperature.

Fluidity of a given membrane decreases at lower ambient temperatures, whereas it rises at increasing temperatures, which is achieved through changes in membrane lipid composition. In consistence with homeoviscous adaptation theory, lower temperatures result in increased tissue concentrations of polyunsaturated fatty acids (PUFAs) in Daphnia magna, suggesting a higher PUFA requirement at lower temperatures. However, so far homeoviscous adaptation has been suggested for single or geographically separated Daphnia genotypes only. Here, we investigated changes in relative fatty acid (FA) tissue concentrations in response to a lower temperature (15°C) within a D. magna population. We determined juvenile growth rates (JGR) and FA patterns of 14 genotypes that were grown on Chlamydomonas klinobasis at 15°C and 20°C. We report significant differences of JGR and the relative body content of various FAs between genotypes at either temperature and between temperatures. Based on slopes of reaction norms, we found genotype‐specific changes in FA profiles between temperatures suggesting that genotypes have different strategies to cope with changing temperatures. In a hierarchical clustering analysis, we grouped genotypes according to differences in direction and magnitude of changes in relative FA content, which resulted in three clusters of genotypes following different patterns of changes in FA composition. These patterns suggest a lower importance of the PUFA eicosapentaenoic acid (EPA, C20:5ω3) than previously assumed. We calculated an unsaturation index (UI) as a proxy for membrane fluidity at 15°C, and we neither found significant differences for this UI nor for fitness, measured as JGR, between the three genotype clusters. We conclude that these three genotype clusters represent different physiological solutions to temperature changes by altering the relative share of different FAs, but that their phenotypes converge with respect to membrane fluidity and JGR. These clusters will be subjected to different degrees of PUFA limitation when sharing the same diet.