Modification of fatty acid composition of lipid accumulating yeasts with cyclopropene fatty acid desaturase inhibitors

Summary The effect of cyclopropene fatty acids, sterculic and malvalic, on the lipids of yeasts grown under nitrogen limiting, lipid accumulating, conditions was studied. The ratio of stearic to oleic acid showed a dose response effect, with an increase in stearic acid content as the dose of cyclopropene fatty acid increased, and a corresponding reduction in oleic acid. Linoleic and linolenic acids were not affected to the same extent. These effects are shown for the yeasts Candida sp. 107, Trichosporon cutaneum, and Rhodosporidium toruloides.     

Development of marker-free transgenic Jatropha plants with increased levels of seed oleic acid

Background

Jatropha curcas is recognized as a new energy crop due to the presence of the high amount of oil in its seeds that can be converted into biodiesel. The quality and performance of the biodiesel depends on the chemical composition of the fatty acids present in the oil. The fatty acids profile of the oil has a direct impact on ignition quality, heat of combustion and oxidative stability. An ideal biodiesel composition should have more monounsaturated fatty acids and less polyunsaturated acids. Jatropha seed oil contains 30% to 50% polyunsaturated fatty acids (mainly linoleic acid) which negatively impacts the oxidative stability and causes high rate of nitrogen oxides emission.

Results

The enzyme 1-acyl-2-oleoyl-sn-glycero-3-phosphocholine delta 12-desaturase (FAD2) is the key enzyme responsible for the production of linoleic acid in plants. We identified three putative delta 12 fatty acid desaturase genes in Jatropha (JcFAD2s) through genome-wide analysis and downregulated the expression of one of these genes, JcFAD2-1, in a seed-specific manner by RNA interference technology. The resulting JcFAD2-1 RNA interference transgenic plants showed a dramatic increase of oleic acid (> 78%) and a corresponding reduction in polyunsaturated fatty acids (< 3%) in its seed oil. The control Jatropha had around 37% oleic acid and 41% polyunsaturated fatty acids. This indicates that FAD2-1 is the major enzyme responsible for converting oleic acid to linoleic acid in Jatropha. Due to the changes in the fatty acids profile, the oil of the JcFAD2-1 RNA interference seed was estimated to yield a cetane number as high as 60.2, which is similar to the required cetane number for conventional premium diesel fuels (60) in Europe. The presence of high seed oleic acid did not have a negative impact on other Jatropha agronomic traits based on our preliminary data of the original plants under greenhouse conditions. Further, we developed a marker-free system to generate the transgenic Jatropha that will help reduce public concerns for environmental issues surrounding genetically modified plants.

Conclusion

In this study we produced seed-specific JcFAD2-1 RNA interference transgenic Jatropha without a selectable marker. We successfully increased the proportion of oleic acid versus linoleic in Jatropha through genetic engineering, enhancing the quality of its oil.     

Punicic acid production in Brassica napus

Punicic acid (PuA; 18:3Δ^{9cis,11trans,13cis}), a conjugated linolenic acid isomer bearing three conjugated double bonds, is associated with various health benefits and has potential for industrial use. The major nature source of this unusual fatty acid is pomegranate (Punica granatum) seed oil, which contains up to 80% (w/w) of its fatty acids as PuA. Pomegranate seed oil, however, is low yielding with unstable production and thus limits the supply of PuA. Metabolic engineering of established temperate oil crops for PuA production, therefore, has the potential to be a feasible strategy to overcome the limitations associated with sourcing PuA from pomegranate. In this study, the cDNAs encoding a pomegranate fatty acid conjugase and a pomegranate oleate desaturase were co-expressed in canola-type Brassica napus. Transgenic B. napus lines accumulated up to 11% (w/w) of the total fatty acids as PuA in the seed oil, which is the highest level of PuA reported in metabolically engineered oilseed crops so far. Levels of seed oil PuA were stable over two generations and had no negative effects on seed germination. The transgenic B. napus lines with the highest PuA levels contained multiple transgene insertions and the PuA content of B. napus seed oil was correlated with efficiency of oleic acid desaturation and linoleic acid conjugation. In addition, PuA accumulated at lower levels in polar lipids (5.0–6.9%) than triacylglycerol (7.5–10.6%), and more than 60% of triacylglycerol-associated PuA was present at the sn-2 position. This study provides the basis for the commercial production of PuA in transgenic oilseed crops and thus would open new prospects for the application of this unusual fatty acid in health and industry.     

Influence of cold temperatures on leaf lipids of Hibiscus rosa-sinensis

Triaclyglycerols (TAG) accounted for 15% of the leaf acyl lipids in a Hibiscus rosa-sinensis plant that survived the January 1986 freeze in Florida, U.S.A. This high TAG level suggested that the plant had cold hardened. The TAG concentration in leaves on new shoots from this plant was greater than that in new leaves on new shoots from five plants frozen to the roots during the freeze. However, five months later, the amounts of TAG in the six Hibiscus plants were nearly the same. The minor differences in TAG levels, however, related to the survival rate of these six plants during subsequent freezes. In addition to linoleic acid, two cyclopropene fatty acids, malvalic and sterculic, were major constituents of the leaf TAG. Hibiscus plants placed in environmental chambers under control and cold-hardening regimes optimized for Citrus showed TAG concentrations of 7% in control and 20% in hardened plants. A survey of neutral lipids in Hibiscus and other plants showed that plastoquinone A (B) and α-tocopherol decreased and plastoquinone C increased under cold-hardening conditions. Polyprenols, a major component of Hibiscus leaves under normal conditions, declined greatly under cold-hardening regimes.     

A novel oxo fatty acid in Plantago ovata seed oil

Plantago ovata seed oil contains two oxygenated fatty acids one of which is the known 9-hydroxyoctadec-cis-12-enoic acid. The other is 9-oxoact     

Fatty Acid Composition of Baobab Seed and Its Relationship with the Genus Adansonia Taxonomy

Baobab seed oil contains specific fatty acids. Most of the studies on baobab fatty acids have been carried out singly and in isolation from each other, making it difficult to compare results through different species. The objective of the present study is to establish the seed fatty acid composition of each Adansonia species in order to evaluate and understand the relationships between the oil chemical compositions, the baobabs’ taxonomy and, the ecological and geographical origin of each seed lot. The seed oils have been analysed using gas chromatography (GC). The oils of all baobab species contain three major fatty acids: palmitic, oleic and linoleic acids. They also contain specific fatty acids such as cyclopropenic and cyclopropanic acids, which are characteristic of the Malvaceae family seed oils. It was possible to distinguish three sections through principal components analysis using the eleven fatty acids identified by GC. The Adansonia section contains high rates of oleic acid (± 35%), the Brevitubae section is rich in palmitic acid (± 42%) and the Longitubae section contains high levels of dihydrosterulic acid (± 5%). The oil fatty acid composition, however, does not enable a definitive characterization of profiles according to species. The fatty acid composition is not significantly influenced by the geographical, soil and climate conditions of the collection sites.     

Epoxyoctadecadienoic acids from Crepis conyzaefolia seed oil

The seed oil of Crepis conyzaefolia (Gouan) Dalle Torre contains previously unidentified (±)-cis-12,13-epoxyoctadeca-trans-6-cis-9-dienoic (14%) and cis-12,13-epoxyoctadeca-cis-6-cis-9-dienoic (2%) acids and the more common vernolic [(±)-12,13-epoxyoctadec-cis-9-enoic] (32%) acid.     

Chemical components of guindilla seeds (Valenzuelia trinervis)

A cyanolipid has been isolated and characterized from Valenzuelia trinervis (guindilla, Sapindaceae). The seed oil contains primarily oleic (62.3%), gadoleic (12.4%), linoleic (10.1%), and palmitic (9.6%) acids. The leaves of this plant contain approximately 25% saponins of which one predominates. The genin appears to be of triterpenoid origin. The seed meal contains ample lysine, leucine and phenylalanine, but is deficient in methionine. The seed meal is toxic to rats.     

Production of nutritionally desirable fatty acids in seed oil of Indian mustard (Brassica juncea L.) by metabolic engineering

Development of a designer oilseed crop with improved yield attributes and enhanced nutritional quality for the benefits of mankind and animal husbandry is now achievable with the combination of genetic engineering and plant breeding. In spite of their immense importance, the fatty acid profiles of most oilseed crops are imbalanced that necessitate the use of metabolic engineering strategies to overcome the various shortfalls in order to improve the nutritional quality of these edible oils. Indian mustard (Brassica juncea L.), being one of the important oilseed crops in Indian subcontinent naturally contains ~50 % nutritionally undesirable very long chain unsaturated fatty acids (VLCUFAs), e.g. erucic acid (C_22:1). For the purpose of nutritional improvement of B. juncea seed oil, several metabolic engineering strategies have been employed to divert the carbon flux from the production of VLCUFAs to other important fatty acids. Stearic acid, being a saturated but nutritionally neutral fatty acid, is naturally inadequate in most of the conventional oil seeds. Due to its neutral effect on consumer’s health and as an important industrial ingredient, increased in planta production of stearic acid in the seed oil not only helps in reduction of production cost but also lessens the trans fatty acid production during commercial hydrogenation process. In this review metabolic engineering strategies to minimize the VLCUFAs along with increased production of stearic acid in the seed oil of B. juncea are discussed, so that further breeding attempts can be made to improve the nutritionally desirable fatty acid profile in the suitable cultivars of this important oilseed crop.     

A new dihydroxy acid from the oil of Peganum harmala

The seed oil of Peganum harmala contains a previously unknown dihydroxy acid characterised as 9,14-dihydroxy octadecanoic acid. P. harmala is the first higher plant found to contain this non-vicinal diol acid (3.2%) in its triglycerides.     

Increasing erucic acid content through combination of endogenous low polyunsaturated fatty acids alleles with Ld-LPAAT + Bn-fae1 transgenes in rapeseed (Brassica napus L.)

High erucic acid rapeseed (HEAR) oil is of interest for industrial purposes because erucic acid (22:1) and its derivatives are important renewable raw materials for the oleochemical industry. Currently available cultivars contain only about 50% erucic acid in the seed oil. A substantial increase in erucic acid content would significantly reduce processing costs and could increase market prospects of HEAR oil. It has been proposed that erucic acid content in rapeseed is limited because of insufficient fatty acid elongation, lack of insertion of erucic acid into the central sn-2 position of the triaclyglycerol backbone and due to competitive desaturation of the precursor oleic acid (18:1) to linoleic acid (18:2). The objective of the present study was to increase erucic content of HEAR winter rapeseed through over expression of the rapeseed fatty acid elongase gene (fae1) in combination with expression of the lysophosphatidic acid acyltransferase gene from Limnanthes douglasii (Ld-LPAAT), which enables insertion of erucic acid into the sn-2 glycerol position. Furthermore, mutant alleles for low contents of polyunsaturated fatty acids (18:2 + 18:3) were combined with the transgenic material. Selected transgenic lines showed up to 63% erucic acid in the seed oil in comparison to a mean of 54% erucic acid of segregating non-transgenic HEAR plants. Amongst 220 F₂ plants derived from the cross between a transgenic HEAR line and a non-transgenic HEAR line with a low content of polyunsaturated fatty acids, recombinant F₂ plants were identified with an erucic acid content of up to 72% and a polyunsaturated fatty acid content as low as 6%. Regression analysis revealed that a reduction of 10% in polyunsaturated fatty acids content led to a 6.5% increase in erucic acid content. Results from selected F₂ plants were confirmed in the next generation by analysing F₄ seeds harvested from five F₃ plants per selected F₂ plant. F₃ lines contained up to 72% erucic acid and as little as 4% polyunsaturated fatty acids content in the seed oil. The 72% erucic acid content of rapeseed oil achieved in the present study represents a major breakthrough in breeding high erucic acid rapeseed.     

Identification of high seed oil yield and high oleic acid content in Brazilian germplasm of winter squash (Cucurbita moschata D.)

Cucurbita moschata D. seed oil contains approximately 75% unsaturated fatty acids, with high levels of monounsaturated fatty acids and antioxidant compounds such as vitamin E and carotenoids, constituting a promising food in nutritional terms. In addition, the Brazilian germplasm of C. moschata exhibits remarkable variability, representing an important source for the genetic breeding of this vegetable and other cucurbits. The present study evaluated the productivity and profile of the seed oil of 91C. moschata accessions from different regions of Brazil maintained in the Vegetable Germplasm Bank of the Federal University of Viçosa (BGH-UFV). A field experiment was conducted between January and July 2016. The accessions showed high genetic variability in terms of characteristics related to seed oil productivity (SOP), such as the weight of seeds per fruit and productivity of seeds, providing predicted selection gains of 29.39 g and 0.26 t ha^?1, respectively. Based on the phenotypic and genotypic correlations, a greater SOP can be achieved while maintaining a high oleic acid concentration and low linoleic acid concentration, providing oil of better nutritional and chemical quality. In the variability analysis, the accessions were clustered into five groups, which had different averages for SOP and fatty acid concentration of seed oil, an approach that will guide the use of appropriate germplasm in programs aimed at genetic breeding for SOP and seed oil profile. Per se analysis identified BGH-4610, BGH-5485A, BGH-6590, BGH-5556A, BGH-5472A, and BGH-5544A as the most promising accessions in terms of SOP, with an average (μ + g) of approximately 0.20 t ha^?1. The most promising accessions for a higher oleic acid concentration of seed oil were BGH-5456A, BGH-3333A, BGH-5361A, BGH-5472A, BGH-5544A, BGH-5453A, and BGH-1749, with an average (μ + g) of approximately 30%, almost all of which were also the most promising in terms of a lower linoleic acid concentration of the seed oil, with an average (μ + g) of approximately 45%. Part of the C. moschata accessions evaluated in the present study can serve as a promising resource in genetic breeding programs for SOP and fatty acid profile, aiming at the production of oil with better nutritional and physicochemical quality.     

Fruit-coat and seed fats of Rhopalostylis, Elaeocarpus and Nestegis species

The fruit-coat fats of Rhopalostylis sapida, R. baueri (Palmae), Elaeocarpus dentatus (Elaeocarpaceae) and Nestegis cunninghamii (Oleaceae) and the seed fats of E. dentatus and N. cunninghamii contain as their major fatty acids palmitic 11–35%, oleic 13–68%, and linoleic 16–31%. The seed fat of E. dentatus contains 10% hexadecenoic acid and the fruit-coat fat of N. cunninghamii 13% linolenic acid.     

Variability for protein and oil quality in Lupinus albus

Amino acid composition and fatty acid composition were determined on seed samples of a range of white lupin (Lupinus albus) cultivars and accessions grown in either of two environments.Variability between genotypes was found for lysine, arginine and glutamic acid content, but not for the concentrations of other amino acids. The deficiency in sulphurcontaining amino acids, typical of legume proteins, was evident, with methionine and cyst(e)ine totalling only 2.2% of the protein. Variability was limited, indicating that improvement by breeding would be impracticable. Lupinus albus differed slightly from other lupin species in amino acid composition, having higher levels of threonine, tyrosine and isoleucine, but a lower level of glutamic acid than both L. angustifolius and L. luteus. Four low-alkaloid lines of L albus each had higher lysine content than the high-alkaloid line, but ‘Kiev Mutant’, despite earlier claims, had a lysine level no higher than the other three low-alkaloid lines.Fatty acid composition of the seed oil varied considerably between genotypes. Oleic acid ranged from 43.6 to 54.4% and linolenic acid from 6.7 to 15.2%, these two fatty acids being negatively correlated at one site. Linoleic acid content varied between 17.2 and 26.9% and was not correlated with other fatty acids. Total oil content averaged 9.6% with little variability between lines.It is concluded that, relative to other lupin species, L. albus has a more favourable amino acid profile for its utilisation in cereal-based diets for animals, particularly if the energy source is wheat, which is deficient in threonine. The higher oil content would be an important energy benefit to such diets and may allow their protein/energy balance to be maintained at higher levels of incorporation of L. albus seed meal than is possible with other lupin species.     

Seed lipids of the lythraceae

Fatty acid composition of seed lipids for 20 of the 26 genera in the Lythraceae and seed oil and protein content for nine genera are reported. The percent oil ranges from 2.7 to 34% of total weight and protein from 11.3 to 24.9%. Linoleic acid is the dominant fatty acid in seed lipids of all genera surveyed. Variations in pattern emphasize palmitic or oleic acid or both as second most abundant lipid component. There are three exceptions: in Diplusodon capric acid ranks second in abundance; in Adenaria lauric acid and oleic acid occur in approximately equal amounts as second most abundant fatty acid; in Decodon an unusual trienoic acid, previously reported only from the Compositae, is the main secondary component. Fatty acid composition of seeds in the genera is compared to that of the previously studied lythraceous genus Cuphea. Among all the genera, only Cuphea seed produces large quantities of lauric, capric, or caprylic acids, as well as a diversity of fatty acid patterns. No relationship between oil content or seed weight and habit is apparent in any genus studied, nor are differences in seed morphology reflected in composition of the seed lipids. The fatty acid patterns are judged evolutionarily conservative, with the strong exception of Cuphea, which remains unique in the Lythraceae and among all angiosperms for the diversity of patterns displayed.     

Mating systems in two species ofPotentilla from Alaska

Aspects of reproductive ecology have been studied in two species ofPotentilla (Rosaceae) from interior Alaska. Data were collected to determine mating system traits such as seed: ovule and pollen: ovule ratios, and experiments were carried out in the field in order to study the effect of caging, emasculation, and manual self-pollination on seed set and seed quality. Mating system strategies differ between the two species in the populations examined. High pollen: ovule ratio, high seed: ovule ratio, good autodeposition ability, and unpredictable pollination in concert with self-incompatibility indicate thatP. hookeriana in the population studied has adopted a more or less pseudogamous mating system. In contrast, the data suggest thatP. uniflora in the studied population is approaching a sexual, facultatively outbreeding species. Because both species exhibit ploidy variation, a trait common among agamospermous plants, it is concluded that both species are likely to be facultatively agamospermous but that sexual reproduction is much more important in the population ofP. uniflora than it is inP. hookeriana.     

(−)-(S,S)-12-hydroxy-13-octadec-cis-9-enolide,a 14-membered lactone from Crepis conyzaefolia seed oil

Crepis conyzaefolia (Gouan) Dalle Torre seed oil contains about 3% of (?)-(S,S)-12-hydroxy-13-octadec-cis-9-enolide (1), a lactone of (?)-threo-12,13-dihydroxyoleic acid. The absolute configuration of the acid has been established as D-12, L-13 (12-S, 13-S) and the lactone has the same absolute configuration.     

Changes in the composition of winter rape oil during seed maturation

The course of biosynthesis of fatty acids in the seeds of winter rape (Brassica napus L. ssp.oleifera, f.biennis cv. T?ebí?ská) was investigated. After the termination of flowering seed samples were taken at five intervals, the seeds were divided into 4 fractions according to size, and their weight, water content, oil content and fatty acid composition were determined. The oil content was found to increase in all size categories with time, with the exception of a minute drop when complete maturity is reached. Larger seeds contained more oil. The fatty acid composition changes with time in the individual size fractions almost continuously. The same holds for differences between seed sizes of the same sample. The main change in oil composition consists in the decrease of C₁₈ acids in favour of C₂₂ acids. Greatest decrements during maturation were found with oleic acid, less with linoleic acid. In absolute amounts the quantity of all synthesized acids rises, the greatest rise being observed with C₂₂ acids (i.e. predominantly erucic acid). It follows from the mean rates of synthesis of the individual groups (C₁₆, C₁₈, C₂₀, C₂₂) of fatty acids that the fraction of C₂₂ rate of synthesis increases, while that of the C₁₈ acids decreases with the same speed. The results indicate that the fatty acid synthesis is most intense during the second half of seed maturation, the main role being played by accelerating the synthesis of higher acids, especially of erucic acid.