Vernolic Acid Research Articles

Leaf lipids from Euphorbia lagascae Spreng. and Euphorbia lathyris L.

The Euphorbiaceae family is comprised of plant species that synthesise unusual fatty acids in their seed oils, e.g., Ricinus communis (ricinoleic or hydroxyoleic acid), Aleurites fordii (eleostearic acid) or Euphorbia lagascae (vernolic or epoxyoleic acid). Accumulation of triacylglycerols (TAGs) in plant leaves of many species can occur, although in smaller quantities than in seeds. This is the first report on leaf lipids in Euphorbia. Total lipid (TL) content ranged from 2274 to 5757 μg/g of fresh weight in Euphorbia lathyris and from 1562 to 9813 μg/g of fresh weight in E. lagascae. The first, fifth, tenth or fifteenth true leaves (each case from 2- to 40-day-old leaves) were sampled from plants grown in the open field and in the glasshouse at Instituto Murciano de Investigación y Desarrollo Agrario y Alimentario (Murcia, Spain). TAGs were separated by thin-layer chromatography (TLC) and represented up to 44.3% of TL in E. lagascae. The amount of TAG peaked in the first leaf and subsequently decreased with aging in all leaves. Microscope preparations revealed the presence of oil bodies (3–10 μm), possibly acting as intermediate storage products, in Euphorbia leaf mesophyll cells. Vernolic acid was identified in E. lagascae leaf lipids (0–25.7% of total fatty acids), but it was not incorporated into TAGs. These results imply that the active enzyme, diacylglycerol acyltransferase (DGAT), in the leaf of E. lagascae does not exhibit any selectivity towards the native unusual fatty acid.

Glutathione half-cell reduction potential as a seed viability marker of the potential oilseed crop Vernonia galamensis

Seeds of Vernonia galamensis (Cass.) Less. contain a high proportion of vernolic acid that is highly desirable for industrial use and emphasises the potential of this species for commercialisation. For successful commercialisation, seed quality during storage must be maintained and regularly assessed, which can be rapidly achieved by using biochemical markers of seed viability. In V. galamensis, three potential viability markers electrolyte leakage (as a measure of membrane integrity) and the antioxidants tocopherol and glutathione were investigated in highly viable, aged and dead seeds at 6% and 12% moisture content (MC). Both electrolyte leakage and tocopherol were not correlated with seed viability whereas the glutathione half-cell reduction potential ( E GSSG/2GSH) correlated strongly with viability loss during seed ageing at both MCs. However, an increase in E GSSG/2GSH associated with viability loss was delayed in the drier seeds (6% MC), highlighting that the performance of this seed viability marker could be decreased in seeds which lose viability in, or close to, the glassy state.

Vernonia DGATs increase accumulation of epoxy fatty acids in oil

Vernolic acid (cis-12-epoxy-octadeca-cis-9-enoic acid) is valuable as a renewable chemical feedstock. This fatty acid can accumulate to high levels in the seed oil of some plant species such as Vernonia galamensis and Stokesia laevis which are unsuitable for large-scale production. A cost-effective alternative for production of epoxy fatty acids is to genetically engineer its biosynthesis in commercial oilseeds. An epoxygenase cDNA (SlEPX) responsible for vernolic acid synthesis and two acyl-CoA : diacylglycerol acyltransferase cDNAs (VgDGAT1 and VgDGAT2) catalysing triacylglycerol (TAG) formation were cloned from developing seeds of S. laevis and V. galamensis. Co-expression of SlEPX and VgDGAT1 or VgDGAT2 greatly increases accumulation of vernolic acid both in petunia leaves and soybean somatic embryos. Seed-specific expression of VgDGAT1 and VgDGAT2 in SlEPX mature soybean seeds results in vernolic acid levels of approximately 15% and 26%. Both DGAT1 and DGAT2 increase epoxy fatty acid accumulation with DGAT2 having much greater impact.

The biosynthesis of cutin and suberin as an alternative source of enzymes for the production of bio-based chemicals and materials

Oxygenated fatty acids such as ricinoleic acid and vernolic acid can serve in the industry as synthons for the synthesis of a wide range of chemicals and polymers traditionally produced by chemical conversion of petroleum derivatives. Oxygenated fatty acids can also be useful to synthesize specialty chemicals such as cosmetics and aromas. There is thus a strong interest in producing these fatty acids in seed oils (triacylglycerols) of crop species. In the last 15 years or so, much effort has been devoted to isolate key genes encoding proteins involved in the synthesis of oxygenated fatty acids and to express them in the seeds of the model plant Arabidopsis thaliana or crop species. An often overlooked but rich source of enzymes catalyzing the synthesis of oxygenated fatty acids and their esterification to glycerol is the biosynthetic pathways of the plant lipid polyesters cutin and suberin. These protective polymers found in specific tissues of all higher plants are composed of a wide variety of oxygenated fatty acids, many of which have not been reported in seed oils (e.g. saturated ω-hydroxy fatty acids and α,ω-diacids). The purpose of this mini-review is to give an overview of the recent advances in the biosynthesis of cutin and suberin and discuss their potential utility in producing specific oxygenated fatty acids for specialty chemicals. Special emphasis is given to the role played by specific acyltransferases and P450 fatty acid oxidases. The use of plant surfaces as possible sinks for the accumulation of high value-added lipids is also highlighted.

Performance of Vernonia galamensis as a potential and viable industrial oil plant in Eritrea: Yield and oil content -1

Vernonia galamensis, whose seeds can be used to produce high-demand, environmentally friendly oil, can stimulate the economy of a country like Eritrea. The seed from the plant contains oil rich in epoxy fatty acids. A potential market use is as a drying agent for resin paints and can form clear, tough, rubbery plastics or coatings on metal. The general objective was to develop vernonia as a viable industrial plant in Eritrea while the specific objectives were to collect, introduce, and characterize wild vernonia accessions and to evaluate and select the best genotypes with higher seed yield and oil content. A total of 61 wild accessions of vernonia were collected from different parts of Eritrea. Some germplasm materials were also added from Ethiopia in 1995 and collections from the United States Department of Agriculture. The materials were collected in its wild form in valleys, riverbanks, plateaus and hills in many parts of Eritrea. The germplasm was collected, characterized and evaluated. The results of the germplasm collection showed that the mean seed yield (kg/ha), seed size (g/1000 seeds), total oil (%) and vernolic acid (%) were 873, 3.4, 24, and 62, respectively. The variety trial of vernonia tested has shown that ERV-05 (1127 kg ha–1) and 66 BK-OR-1 (1111 kg ha–1) were the best yielding genotypes. The oil content of ERV-05 was better than 66BK-OR-1. The genotypes with smaller seed size had better oil content. There was a positive and significant correlation between oil content, plant height and days to blooming. Therefore, breeders should select genotypes based on these traits for better oil content. The future challenges of the plant are lack of uniform seed maturity, and to develop appropriate technologies for mechanical harvesting, seed cleaning and processing and oil extraction.

An epoxide hydrolase involved in the biosynthesis of an insect sex attractant and its use to localize the production site

Epoxide hydrolases (EHs) are enzymes occurring in virtually any living organism. They catalyze the hydrolysis of epoxide containing lipids and are involved in crucial mechanisms, such as the detoxification of xenobiotics or the regulation of inflammation and blood pressure. Here, we describe a function of a putative EH gene in the biosynthesis of a sex attractant in the jewel wasp Nasonia vitripennis and use this gene to localize the site of pheromone production. Males of this parasitic wasp release a mixture of (4R,5R)-( threo-) and (4R,5S)-( erythro-)5-hydroxy-4-decanolide (HDL) to attract virgin females. Using a stable isotope labeled precursor, we demonstrated that vernolic acid ( erythro-12,13-epoxy-octadec-9Z-enoic acid) is converted by N. vitripennis males to threo-HDL. This suggested the involvement of an EH in hydrolyzing the fatty acid epoxide under inversion of the stereochemistry into the respective diol, which might be further processed by chain shortening and lactonization to HDL. We cloned a putative N. vitripennis EH gene (Nasvi-EH1) encoding 470 amino acids and localized its transcripts in the male rectal papillae by in situ RT-PCR. Chemical analyses and histological studies confirmed that males synthesize the sex attractant in the rectal vesicle and release it via the anal orifice. Involvement of Nasvi-EH1 in HDL biosynthesis was established by RNAi-mediated gene silencing. Injection of Nasvi-EH1 dsRNA into male abdomens inhibited pheromone biosynthesis by 55% and suppressed the targeted gene transcripts in the rectal vesicle by 95%.

Synthesis of novel cationic bolaamphiphiles from vernonia oil and their aggregated structures

The present study describes the synthesis of a novel class of vesicle-forming bolaamphiphiles with choline ester head groups. These bolaamphiphiles were derived from vernonia oil, whose main constituent is vernolic acid, a fatty acid with a unique combination of epoxy, carboxy and unsaturated double bonds. A series of bolaamphiphiles containing amido or ester groups within the hydrophobic domain were synthesized from N, N′-alkylenebis (vernolamides) and α,ω-alkylene divernolate ester in a two-stage synthesis comprising opening of the epoxy ring with chloroacetic acid, followed by quaternization with N, N-dimethylaminoethyl acetate to form choline ester head groups. The products were characterized by FT-IR, 1H and 13C NMR, and ESI-MS. Vesicles prepared from these bolaamphiphiles have the potential to serve as a targeted drug delivery systems with selective decapsulation in the presence of the enzyme acetylcholine esterase, resulting in site-specific release of the drug.

Cloning and functional analysis of two type 1 diacylglycerol acyltransferases from Vernonia galamensis

Vernonia galamensis accumulates vernolic acid ( cis-12-epoxyoctadeca- cis-9-enoic acid) as the major fatty acid in its seed oil. Such epoxy fatty acids are useful in a number of industrial applications. Successful genetic engineering of commercial oilseed crops to produce high levels of vernolic acid depends on a better understanding of the source plant enzymes for vernolic acid accumulation. Developing V. galamensis seed microsome assays demonstrate that diacylglycerol acyltransferase (DGAT), an enzyme for the final step of triacylglycerol synthesis, has a strong substrate preference for vernolic acid bearing substrates including acyl-CoA and diacylglycerol. There are two classes of DGATs known as DGAT1 and DGAT2. Here we report on the isolation, characterization, and functional analysis of two DGAT1 cDNAs from V. galamensis ( VgDGAT1a and VgDGAT1b). VgDGAT1a and VgDGAT1b are expressed in all plant tissues examined with highest expression in developing seeds. Enzymatic assays using isolated microsomes from transformed yeast show that VgDGAT1a and VgDGAT1b have the same DGAT activity levels and substrate specificities. Oleoyl-CoA and sn-1,2-dioleoylglycerol are preferred substrates over vernoloyl-CoA and sn-1,2-divernoloylglycerol. This data indicates that the two VgDGAT1s are functional, but not likely to be responsible for the selective accumulation of vernolic acid in V. galamensis seed oil.

Performance of Vernonia as an Alternative Industrial Oil Crop in Limpopo Province of South Africa

Vernonia (Vernonia galamensis) is an industrial oil seed crop with potential as a source of natural epoxy fatty acids. Diverse accessions of V. galamensis var. ethiopica were studied at the Limpopo Province in South Africa to determine agronomic performance and to identify suitable germplasm with quantity and quality seed oil content. Thirty‐six accessions were subjected to field evaluations using a partially balanced lattice design in 2005 and 2006. Significant differences were observed for days to flowering (88–143 d), plant height (131.6–167.85 cm), number of productive primary head (23–72 head plant−1), number of productive secondary head (12–35 head plant−1), thousand seed weight (1.68–3.63 g), and seed yield (1594.89– 3126.09 kg ha−1) between different accessions. Results from oil analysis show significant differences in the contents of seed oil (20.36–35.86%), vernolic acid (70.15–77.92%), linoleic acid (12.05–14.73%), oleic acid (3.72–5.52%), palmitic acid (2.49–3.24%), and stearic acid (1.73–3.28%). Of the five accessions identified as potentially useful, three (Vge‐17, Vge‐18, and Vge‐19) had better seed yield and agronomic performances and two (Vge‐4 and Vge‐31) increased contents of seed oil and vernolic acid. Accessions Vge‐4 and Vge‐18 also displayed relatively high oil yield, 966.58 and 801.28 kg ha−1, respectively. The accessions will be used in the stra tegic improvement of vernonia to maximize seed yield and oil content as an alternative crop in the province and similar environments.

Fatty Acids in Vernonia Produced in the Mid‐Atlantic Region of the United States

AbstractVernonia galamensis [(Cass.) Less.] is a native of Ethiopia and Eritrea. Seed of vernonia contain substantial quantities of naturally epoxidized oil, which is used in the paint industry to reduce emissions of volatile organic compounds that produce smog resulting from the use of petroleum‐based (alkyd‐resin) paint. Epoxidized oil is also used in the manufacture of plasticizers, additives to polyvinyl chloride, polymer blends and coatings, and cosmetic and pharmaceutical applications. Previous research has indicated that vernonia has potential for commercialization in the mid‐Atlantic region of the United States. This study characterized fatty acids in oil from vernonia grown in this latter region. Vernonia oil, from 14 vernonia lines grown during 1995 and 1996 under field conditions in Virginia, contained 3.3, 3.0, 5.0, 15.0, 0.2, 0.5, 0.4, and 72.7%, respectively, of C16:0, C18:0, C18:1, C18:2, C18:3, C20:0, C20:1, and vernolic (C18:1 epoxy) fatty acids. Effects of genotypes on vernonia oil quality were generally not significant whereas the effects of years were significant. The concentration of vernolic acid was positively correlated with oil concentration but negatively correlated with concentrations of all individual fatty acids, except for C18:3.

Characterization of SCP‐2 from Euphorbia lagascae reveals that a single Leu/Met exchange enhances sterol transfer activity

Sterol carrier protein-2 (SCP-2) is a small intracellular basic protein domain implicated in peroxisomal beta-oxidation. We extend our knowledge of plant SCP-2 by characterizing SCP-2 from Euphorbia lagascae. This protein consists of 122 amino acids including a PTS1 peroxisomal targeting signal. It has a molecular mass of 13.6 kDa and a pI of 9.5. It shares 67% identity and 84% similarity with SCP-2 from Arabidopsis thaliana. Proteomic analysis revealed that E. lagascae SCP-2 accumulates in the endosperm during seed germination. It showed in vitro transfer activity of BODIPY-phosphatidylcholine (BODIPY-PC). The transfer of BODIPY-PC was almost completely inhibited after addition of phosphatidylinositol, palmitic acid, stearoyl-CoA and vernolic acid, whereas sterols only had a very marginal inhibitory effect. We used protein modelling and site-directed mutagenesis to investigate why the BODIPY-PC transfer mediated by E. lagascae SCP-2 is not sensitive to sterols, whereas the transfer mediated by A. thaliana SCP-2 shows sterol sensitivity. Protein modelling suggested that the ligand-binding cavity of A. thaliana SCP-2 has four methionines (Met12, 14, 15 and 100), which are replaced by leucines (Leu11, 13, 14 and 99) in E. lagascae SCP-2. Changing Leu99 to Met99 was sufficient to convert E. lagascae SCP-2 into a sterol-sensitive BODIPY-PC-transfer protein, and correspondingly, changing Met100 to Leu100 abolished the sterol sensitivity of A. thaliana SCP-2.

The Crystal Structure of Arabidopsis thaliana Allene Oxide Cyclase: Insights into the Oxylipin Cyclization Reaction

We describe the crystallization and structure elucidation of Arabidopsis thaliana allene oxide cyclase 2 (AOC2), a key enzyme in the biosynthesis of jasmonates. In a coupled reaction with allene oxide synthase, AOC2 releases the first cyclic and biologically active metabolite, 12-oxo-phytodienoic acid (OPDA). AOC2 (AT3G25770) folds into an eight-stranded antiparallel beta-barrel with a C-terminal partial helical extension. The protein forms a hydrophobic binding cavity with two distinct polar patches. AOC2 is trimeric in crystals, in vitro and in planta. Based on the observed folding pattern, we assigned AOC2 as a low molecular weight member of the lipocalin family with enzymatic activity in plants. We determined the binding position of the competitive inhibitor vernolic acid (a substrate analog) in the binding pocket. Based on models for bound substrate 12,13-epoxy-9,11,15-octadecatrienoic acid and product OPDA, we propose a reaction scheme that explains the influence of the C15 double bond on reactivity. Reaction is promoted by anchimeric assistance through a conserved Glu residue. The transition state with a pentadienyl carbocation and an oxyanion is stabilized by a strongly bound water molecule and favorable pi-pi interactions with aromatic residues in the cavity. Stereoselectivity results from steric restrictions to the necessary substrate isomerizations imposed by the protein.

Diacylglycerol acyltransferases from Vernonia and Stokesia prefer substrates with vernolic acid

Genetic engineering of common oil crops for industrially valuable epoxy FA production by expressing epoxygenase genes alone had limited success. Identifying other key genes responsible for the selective incorporation of epoxy FA into seed oil in natural high accumulators appears to be an important next step. We investigated the substrate preferences of acyl CoA:diacylglycerol acyltransferases (DGAT) of two natural high accumulators of vernolic acid, Vernonia galamensis and Stokesia laevis, as compared with a common oilseed crop soybean. Developing seed microsomes were fed with either [14C]oleoyl CoA or [14C] vernoloyl CoA in combinations with no exogenous DAG or with 1,2-dioleoyl-sn-glycerol, 1-palmitoyl-2-vernoloyl-sn-glycerol, 1,2-divernoloyl-sn-glycerol, 1,2-dioleoyl-rac-glycerol, or 1,2-divernoloyl-rac-glycerol to determine their relative incorporation into TAG. The results showed that in using sn-1,2-DAG, the highest DGAT activity was from the substrate combination of vernoloyl CoA with 1,2-divernoloyl-sn-glycerol, and the lowest was from vernoloyl CoA or oleoyl CoA with 1,2-dioleoyl-sn-glycerol in both V. galamensis and S. laevis. Soybean DGAT was more active with oleoyl CoA than vernoloyl CoA, and more active with 1,2-dioleoyl-sn-glycerol when oleoyl CoA was fed. DGAT assays without exogenous DAG, or with exogenous sn-1,2-DAG fed individually or simultaneously showed consistent results. In combinations with either oleoyl CoA or vernoloyl CoA, DGAT had much higher activity with rac-1,2-DAG than with their corresponding sn-1,2-DAG, and the substrate selectivity was diminished when rac-1,2-DAG were used instead of sn-1,2-DAG. These studies suggest that DGAT action might be an important step for selective incorporation of vernolic acid into TAG in V. galamensis and S. laevis.

Lipids as renewable resources: current state of chemical and biotechnological conversion and diversification

Oils and fats are the most important renewable raw materials of the chemical industry. They make available fatty acids in such purity that they may be used for chemical conversions and for the synthesis of chemically pure compounds. Oleic acid (1) from "new sunflower," linoleic acid (2) from soybean, linolenic acid (3) from linseed, erucic acid (4) from rape seed, and ricinoleic acid (5) from castor oil are most important for chemical transformations offering in addition to the carboxy group one or more C-C-double bonds. New plant oils containing fatty acids with new and interesting functionalities such as petroselinic acid (6) from Coriandrum sativum, calendic acid (7) from Calendula officinalis, alpha-eleostearic acid (8) from tung oil, santalbic acid (9) from Santalum album (Linn.), and vernolic acid (10) from Vernonia galamensis are becoming industrially available. The basic oleochemicals are free fatty acids, methyl esters, fatty alcohols, and fatty amines as well as glycerol as a by-product. Their interesting new industrial applications are the usage as environmentally friendly industrial fluids and lubricants, insulating fluid for electric utilities such as transformers and additive to asphalt. Modern methods of synthetic organic chemistry including enzymatic and microbial transformations were applied extensively to fatty compounds for the selective functionalization of the alkyl chain. Syntheses of long-chain diacids, omega-hydroxy fatty acids, and omega-unsaturated fatty acids as base chemicals derived from vegetable oils were developed. Interesting applications were opened by the epoxidation of C-C-double bonds giving the possibility of photochemically initiated cationic curing and access to polyetherpolyols. Enantiomerically pure fatty acids as part of the chiral pool of nature can be used for the synthesis of nonracemic building blocks.

Variation of oil content and fatty acid composition in selected lines of vernonia (Vernonia galamensis variety ethiopica)

Vernonia (Vernonia galamensis) is a new industrial crop that could offer a naturally epoxidized oil with great economic value. The oil content and fatty acid composition of 10 selected lines of V. galamensis variety ethiopica were analysed to study the variability among and within lines. Lines showed oil content varying from 24–29% and varying ranges of vernolic acid (7377%), linoleic acid (12–14%), oleic acid (3.5–5.5%), palmitic acid (2.4–2.9%) and stearic acid (2.3–2.8%). Entries collected from southern Ethiopia had higher oil content than those from eastern Ethiopia. Two accessions, Vge-10 with the highest contents of oil (29%) and vernolic acid (77%) and Vge-3 with the highest vernolic acid content (77%) were identified as promising parents for improving the quantity of oil and vernolic acid.

Combined transgenic expression of Δ12-desaturase and Δ12-epoxygenase in high linoleic acid seeds leads to increased accumulation of vernolic acid.

The transgenic production of unusual fatty acids in oil seed crops offers an alternative, renewable resource for industry. However, transgenic expression of genes catalysing the synthesis of unusual fatty acids has generally resulted in these fatty acids accumulating at levels significantly below the levels in the wild species from which the genes were sourced. This study reports expression of additional copies of any of three Δ12-desaturase genes (FAD2) from Crepis palaestina Bornm., cotton (Gossypium hirsutum L.) or Arabidopsis thaliana (L.) Heynh. with C. palaestina Δ12-epoxygenase gene (Cpal2), in an Arabidopsis mutant having a significantly higher level of linoleic acid substrate. This resulted in the highest levels of vernolic acid accumulation, 21% of total fatty acids, reported so far in any transgenic plant expressing the Δ12-epoxygenase. Similarly, the co-expression of C. palaestina Cpal2 and a transgenic copy of FAD2 in cotton seed that contains large amounts of linoleic acid substrate also resulted in greater accumulation of vernolic acid in seed than did expression of C. palaestina Cpal2 alone.

Exploration of Vernonia galamensis in Ethiopia, and Variation in Fatty Acid Composition of Seed Oil

Vernonia galamensis is a new potential industrial crop with very high content of vernolic acid in the seed oil. The species is known to naturally grow as a weed in fields or in woodlands under a wide range of agroecological conditions of Africa. In order to study the existing variability in Ethiopia, germplasm collection was carried out. Vernonia grows wild in various ecosystems. Ten regions were explored from North, South, East, Southeast, Southwest and Central Ethiopia. A diverse range of habitats having different altitudes and ecological conditions was explored. Altitude of collecting sites varied between 1250 and 2050 m, and soil pH from 5.1 to 8.5. The most common soil type was sandy loam, and the organic matter content varied from 0.2% to 12.9%. At 80 sites, about 480 accessions were collected including different maturity time, plant type, flower color, and branching patterns as well as fatty acid composition. The mean vernolic acid content of the seed oil of the accessions was 74%, and ranged from 34% to 87%. A wide variability in composition of other fatty acids was observed. It was not possible to find Vernonia in some locations that were earlier indicated by herbarium specimens collected since 1840. This could be a sign of change in land use system and environmental degradation and, hence, loss of genetic resources of the species.

Novel Cationic Amphiphilic Derivatives from Vernonia Oil: Synthesis and Self-Aggregation into Bilayer Vesicles, Nanoparticles, and DNA Complexants

Self-assembling nanostructures were prepared from novel cationic amphiphilic compounds synthesized from vernonia oil, a natural epoxydized triglyceride. The presence of a 12,13-epoxy group on the C18 unsaturated fatty acid, vernolic acid, which is the main constituent of vernonia oil, permitted the synthesis of novel amphiphilic derivatives with a hydrogen-bonding hydroxyl and a cationic headgroup moiety on adjacent carbon atoms. The amphiphiles were prepared in a two-stage synthesis that comprised opening of the epoxy groups with a haloacetic acid, followed by quaternization of the halo group with a tertiary amine containing a C12 aliphatic chain. Intact vernonia oil as the starting material gave a triple-headed cationic amphiphile, containing three vernolic acid derived moieties connected through a glycerol backbone. A single-headed amphiphile with two alkyl chains and a single quaternary ammonium headgroup was synthesized from the methyl ester of vernolic acid as the starting material. The triple-headed derivative could form nonencapsulating structures. Cholesterol was required in the formulation (1:1) to make spherical vesicles that could encapsulate a water-soluble marker. The single-headed derivative, however, formed spherical encapsulating vesicles without cholesterol. TEM, NMR, and FT-IR were used to characterize the vesicles, and molecular structure vs morphology relationships were postulated on the basis of these data. The triple-headed amphiphile also formed a DNA complex that was highly resistant to hydrolysis by DNase. This amphiphile-DNA complex was used as vector for gene transfer in cell culture demonstrating efficient DNA transfection.

Quantitative Deuterium Isotopic Profiling at Natural Abundance Indicates Mechanistic Differences for Δ12-Epoxidase and Δ12-Desaturase in Vernonia galamensis

Quantitative (2)H NMR spectroscopy can determine the natural abundance ((2)H/(1)H) ratio at each site of a molecule. In natural products, variation in these values is related to the reaction mechanisms in the pertinent biosynthetic pathway. For the first time, this novel approach has been exploited to probe for mechanistic differences in the introduction of different functionalities into a long-chain fatty acid. Vernolic acid, a major component of the seed oil of Vernonia galamensis, contains both an epoxide and a desaturation. The site-specific isotopic distribution ((2)H/(1)H)(i) has been determined for both vernolic acid and linoleic acid isolated from the same V. galamensis oil. It is found that the ((2)H/(1)H) ratio of vernolic acid shows a pattern along the entire length of the chain, consistent with linoleic acid being its immediate precursor. Notably, the C13 relates to the C13 of linoleic acid but not to the C13 of oleic acid. Furthermore, the C12 and C13 positions in vernolic acid are less depleted, consistent with a change in hybridization state from sp(2) to sp(3). However, the C11 position shows a marked relative enrichment in the vernolic acid, implying that it plays a role in the epoxidase but not the desaturase mechanism. Thus, although it can be concluded that the catalytic mechanisms for the epoxidase and desaturase activities are similar, marked differences in the residual ((2)H/(1)H) patterns indicate that the reaction mechanisms are not identical.

Genetic variability and interrelationship of traits in the industrial oil crop Vernonia galamensis

Vernonia galamensis is a wild plant from the family Asteraceae which is endemic to East Africa and has the potential to become a new oil crop for industrial uses. Its seed oil is rich in vernolic acid, a fatty acid of high interest for oleochemical applications. However, a breeding program for Vernonia galamensis cultivars with high seed and oil yields requires knowledge about the genetic variability of traits that influence seed and oil production. This study was undertaken to examine phenotypic and genotypic variability, broad-sense heritability, genetic advance under selection and interrelationships of agronomic and seed quality traits. A total of 122 Vernonia accessions, 115 collected from different regions of Ethiopia and seven introduced, were grown at two locations in Ethiopia (Alemaya and Babile), in 2001/2002 and were analyzed for 20 traits including phenology, yield, yield components, and seed quality with special emphasis on fatty acid composition. The collections exhibited significant variation for all traits except for days to emergence. Genotypes and locations interacted significantly (P≤ 0.01) for all traits. Broad-sense heritability estimates ranged from 11% (for days to emergence) up to 79% (for days to maturity). Expected genetic advance was between 1.3% (for days to emergence) and 44.8% (for seed oil yield). Genetic correlation analysis revealed that seed yield per plant is highly and positively correlated with seed weight and head number; highly significant and negative correlations (r = −0.59, −0.82, −0.85, and −0.89) were found between vernolic acid and palmitic, stearic, oleic, and linoleic acid, respectively. Highly significant positive correlations (r = 0.55, 0.44, and 0.36) were observed between vernolic acid and oil content, meal protein content and seed oil yield, respectively. Path-coefficient analysis indicated seed weight and secondary head number to be the most important components of seed yield per plant. Vernolic acid, oleic acid and linoleic acid had positive direct effects and stearic acid had a negative direct effect on oil content. The direct positive effect of oleic acid on oil content was, however, compensated by the negative indirect effects of stearic and vernolic acid resulting in a negative correlation (r = −0.60) between oleic acid and oil content. These observations will support the selection of accessions with high seed and oil yield, high meal protein contents, and high vernolic acid content.