Plant Fatty Acid Research Articles

Evaluation of four derivatization methods for the analysis of fatty acids from green leafy vegetables by gas chromatography.

Green leafy vegetables are valuable secondary sources of nutrients, including lipids, commonly consumed in developing countries. However, method development for the analysis of fatty acids is usually focused on the animal lipid samples, rarely including natural plant extracts. Hence, the usefulness of four derivatization methods for the gas chromatographic analysis of plant lipids was studied. Methylation using 10% solution of BF3 in methanol and 2.0M solution of (trimethylsilyl)diazomethane (TMSD) in hexane, trimethylsilylation and tert-butyldimethylsilylation were compared using lipid standards and extracts from the leaves of Solanum macrocarpon and S. melongena after saponification. While silylation was found effective and precise using lipid standards, it initially did not perform well in the analysis of plant lipids due to the presence of transesterification products in samples. Optimization of the hydrolysis conditions resulted in an effective analysis of these derivatives, but poor separation of FA(18:0) from unsaturated FA(18:X) compounds and the presence of larger amounts of interferences disqualified the use silylation for the analysis of plant fatty acids in applied analytical conditions. Methylation using TMSD gave more precise quantitative results when compared to BF3/MeOH method. Also, it produced a significantly lower amount of interferences when applied to plant lipid samples. Additionally, the TMSD-based method is simple, safe and less time-consuming when compared to other procedures. Thus, we suggest using TMSD-based methylation as a method of choice in the GC analysis of plant-derived fatty acids.

A Review of Vegetable Oil-Based Polymers: Synthesis and Applications

The reviewed work addressed the shift in focus from conventional polymers to bio-based and renewable polymers. The environmental attributes of the renewable polymers make them preferred choice of matrix. The properties of the matrices from renewable origin could compete in high end applications. The composition of the fatty acids in plant seed oil was discussed and the determination of the level of unsaturation used the iodine value. This review also extensively discussed the values of various fatty acid components present in the oils. Areas of application of the thermosetting polymers obtained from plant seed oils were also discussed.

Opportunities and Implications of Pasture-Based Lamb Fattening to Enhance the Long-Chain Fatty Acid Composition in Meat.

Health-conscious consumers following dietary fat recommendations require meat that is low in saturated fat with preferably high levels of long-chain omega-3 fatty acids. This review summarizes the influence of dietary lipids from red meat on human health and examines the potential to enhance lipid composition through pasture-feeding. The role of fatty acids in plant and ruminant metabolism is discussed to highlight the complexity of ruminal digestion when trying to enhance fatty acids in meat. Generally, ruminants that consume pasture diets have been shown to produce a more desirable fatty acid composition than those fed grain and offer potential to be further enhanced by using specific plant species. Elevated polyunsaturated fat content in meat, however, tends to increase susceptibility to oxidation, which influences other meat quality characteristics including shelf-life and color. The use of specific plant species may mitigate these negative effects due to vitamin E or other antioxidants in these plants, which protect polyunsaturated fats from oxidation. When assessing the potential of plants as a natural dietary fat source, consideration must be given to environmental influences on plant fatty acid composition to ensure consistent production of meat products with high nutritive value under a range of management practices. This review also explores the potential impact of climate change on plant fatty acid composition, and the potential implications of this for meat quality.

Cloning and Function Characterization of a β-Ketoacyl-acyl-ACP Synthase I from Coconut (Cocos nucifera L.) Endosperm

Coconuts contain beneficial medium-chain fatty acids (MCFAs), particularly lauric acid. The mechanism by which coconuts accumulate MCFAs has been a topic of research because of increasing energy demands. β-Ketoacyl-ACP synthase (KAS) I, a requisite enzyme for chain length regulation in plants, was isolated from coconut endosperm complementary DNA (cDNA) libraries and designated CocoKASI (GenBank accession: JX275887). CocoKASI contained an open reading frame (ORF) of 1485 bp encoding a polypeptide of 494 amino acids (nucleotide positions 134–1618). Expression of CocoKASI determined by fluorescence quantitative real-time PCR was 60 % higher in developing coconut endosperm than in leaves. Fatty acid profiles of endosperm at two different stages showed that the levels of C8:0, C10:0, C12:0, C14:0, and C18:0 increased, while the relative compositions of other fatty acid species, especially C16:0, C18:1, and C18:3, were reduced. Overexpression of CocoKASI cDNA using the seed-specific tobacco (Nicotiana tabacum L.) napin promoter increased short-chain and MCFAs from C6:0 to C16:0, although CocoKASI transcript levels varied 100-fold in tobacco seeds from different transgenic plants. These data suggested that CocoKASI had a preference for catalyzing the elongation of C4:0–C14:0 on ACP to yield C6:0–C16:0 fatty acids in plants. This result was similar to the findings reported for KASI in other species. This study characterized and determined the function of KASI from a tropical oil crop. The results give insights into the regulation of fatty acid biosynthesis and the accumulation of MCFAs in higher plants. The findings will contribute to the engineering, altering, and accumulation of short-chain and MCFAs to meet energy demands.

Novel reactions in acyl editing of phosphatidylcholine by lysophosphatidylcholine transacylase (LPCT) and acyl-CoA:glycerophosphocholine acyltransferase (GPCAT) activities in microsomal preparations of plant tissues

Main conclusion Plants have lysophosphatidylcholine transacylase (LPCT) and acyl-CoA:glycerophosphocholine acyltransferase (GPCAT) activities. The combined action of LPCT and GPCAT provides a novel route of PC re-synthesis after its deacylation. Phosphatidylcholine (PC) is the major lipid in eukaryotic membranes and has a central role in overall plant lipid metabolism. It is also the site of production of polyunsaturated fatty acids in plants. The recently discovered acyl-CoA:glycerophosphocholine acyltransferase (GPCAT) activity in yeast provides a novel route of re-synthesising PC via lysophosphatidylcholine (LPC) after its deacylation. This route does not require the degradation of the glycerophosphocholine (GPC) into free choline, the activation of choline to CDP-choline, nor the utilization of CDP-choline by the CDP-choline:diacylglycerol cholinephosphotransferase. We show here that GPCAT activities also are present in membrane preparations from developing oil seeds of safflower and other species as well as in membrane preparations of roots and leaves of Arabidopsis, indicating that GPCAT activity plays a ubiquitous role in plant lipid metabolism. The last step in formation of GPC, the substrate for GPCAT, is the deacylation of LPC. Microsomal membranes of developing safflower seeds utilized LPC in LPC:LPC transacylation reactions (LPCT activities) creating PC and GPC. The results demonstrate that safflower membranes have LPCT and GPCAT activities that represent novel reactions for PC acyl editing. The physiological relevance of these reactions probably has to await identification of the enzymes catalysing these reactions.

Diversity in KCS2 (Ketoacyl-CoA Synthase) of selected plants and its molecular implications: A computational analysis

The majority of calories in human food are derived from plant fatty acids. Besides,plant fatty acids are also a major component of a variety of products useful to human beings such as paints, cosmetics, biofuels, lubricants, detergents and soaps. Ketoacyl-CoA synthase is a key enzyme involved in the fatty acid elongation in plants In this study, we have analyzed the diversity in the KCS2 proteins of a selected plant species. We conclude that though there are extensive similarities in the KCS2 proteins studied with respect to total number of negatively charged residues, total number of positively charged residues, and domain organization, there are notable differences for other features such as extinction coefficients, protein stability, kinase specific phosphorylation sites, number of O-GlcNAc sites, predicted sumoylation sites, residues contributing to nuclear export signal and transmemebrane helices. These differences may have repercussions for the quantitative efficiency of the 3-Ketoacyl-CoA synthase enzyme which catalyzes the condensation of c2 units to acyl coA during the fatty acid elongation process, and its regulation. This paper showcases molecular implications of diversity in KCS2 , which can be used to create a diverse genetic base for engineering KCS 2 genes.

Effect of dietary substitution of fish oil with flaxseed or sunflower oil on muscle fatty acid composition in juvenile steelhead trout (Oncorhynchus mykiss) reared at varying temperatures

Abstract The effect of changing temperature on muscle fatty acid composition was examined in juvenile steelhead trout (~ 120 g) with complete substitution of fish oil (herring oil; HE) with either flax seed oil (FLX; also known as linseed oil) or sunflower oil (SF). The temperature was increased from ~ 10.0 °C to 18.0 °C following seasonal temperature changes in ~ 2 °C incremental steps with plateaus. Dietary lipid analysis showed the HE diet was rich in marine lipids, docosahexaenoic acid (DHA, 22:6ω3), eicosapentaenoic acid (EPA, 20:5ω3) and docosapentaenoic acid (DPA, 22:5ω3). In contrast FLX was rich in linolenic acid (ALA, 18:3ω3) and SF in linoleic acid (LA, 18:2ω6). Both diet and temperature had no significant effect on growth but significant effects were observed on muscle fatty acid composition. Proportions of marine fatty acids in HE fed fish were significantly higher than in both SF and FLX fish at the end (41, 31 and 31% respectively), with significantly lower levels of terrestrial plant fatty acids compared to the beginning of the experiment. Substitution of SF and FLX had a direct influence on muscle EPA:AA and ω6:ω3 ratios which could be detrimental to the health of the fish, as well as to the quality of the end product for human consumption.

Transgenic production of omega-3 very long chain polyunsaturated fatty acids in plants: Accomplishment and challenge

Abstract Omega-3 very long chain polyunsaturated fatty acids (VLC-PUFAs or VLCPUFAs) such as eicosapentaenoic acid (EPA, 22:5n-3) and docosahexaenoic acid (DHA, 22:6n-3) have important roles in human health. The current source of these fatty acids is oil from marine fish and oleaginous microorganisms. However, sustainability of this source is questionable due to the declining fish population in ocean as well as the high cost associated with the microbial culturing and oil extraction. Transgenic plants producing a high level of VLCPUFAs have been proposed to be a potential alternative source for these fatty acids. Detections of EPA and DHA in transgenic plants expressing heterologous desaturases and elongases as well as a PUFA synthase from VLCPUFA-producing microorganisms have indeed optimistically proven the concept. However, the yield of VLCPUFAs in transgenics is still low and the desirable composition of these fatty acids is not achieved. This mini-review discusses what has been done on the reconstitution of VLCPUFA-biosynthetic pathways in transgenics and what kind of challenges and possible solutions could be in producing VLCPUFAs in plants.

Thermo-oxidation, friction-reducing and physicochemical properties of ricinoleic acid based-diester biolubricants

A major global effort is currently underway to reduce dependence on petroleum products and minimize the impact of their derivatives on the environment. Plant oils are being investigated as a potential source of environmentally favorable lubricants given their combination of biodegradability, renewability and excellent lubrication performance. Low oxidation and thermal stability, poor low-temperature properties and a narrow range of available viscosities, however, limit their potential application as industrial biolubricants. The chemical modification of plant fatty acid structures has great potential for improving the physicochemical and friction-reducing properties of these compounds. This paper presents the thermo-oxidation, friction-reducing and physicochemical properties of a series of diester compounds derived from ricinoleic acid as biolubricant basestocks. The results indicated that among the synthesized ricinoleic acid-based diester compounds, octyl 10,12-dihydroxy-9-behenoxystearate 16 has the lowest pour point (−53.26°C), while octyl 10,12-dihydroxy-9-octyloxystearate 10 has the highest onset temperature (128.98°C) and the lowest volatile loss and quantity of insoluble deposits (68.78% and 77.25%, respectively). The friction-reducing results indicate an improvement occurred in the presence of longer mid-chain esters and an increased polarity in the ester functional group. The data indicate that some synthesized derivatives have significant potential as environmentally friendly biolubricant basestocks.

Functional expression of Brassica juncea oleate desaturase gene (Bjfad2) in Escherichia coli

The synthesis of polyunsaturated fatty acids, the most abundant fatty acids in plants, begins with a reaction catalyzed by fatty acid desaturase-2 (FAD2; EC 1.3.1.35), also called as microsomal Δ12 oleate desaturase. The gene (Bjfad2; GenBank accession No. EF639848) coding for this enzyme from Brassica juncea was previously isolated and characterized. However, functional identity of Bjfad2 was not established. Utilizing the known Bjfad2 cDNA sequence, the ORF of Bjfad2 gene was cloned into the pMAL C2X Escherichia coli expression vector and produced recombinant plasmid by insertion of isolated ORF downstream to the maltose-binding protein coding sequence. The pMALC2X-Bjfad2 vector was used to transform the TB1 strain of E. coli. Induced expression of pMAL-BJFAD2 fused product resulted in the synthesis of a polypeptide with an apparent molecular mass of 80 kDa, which was 8 kDa less than calculated mass as determined by SDS-PAGE, since the fused MalE-Bjfad2 gene contains eight additional codons located between the MalE and Bjfad2 gene. In vitro activity assay of oleate desaturase using the corresponding bacterial crude extracts confirmed that the polypeptide was the product of the Bjfad2 gene. The reaction products analysis of the fatty acid methyl esters by gas chromatography showed the presence of a new peak with a similar retention time to linoleic acid, which was absent in the control activity assay without electron donors. Thus, B. juncea gene has been functionally identified since it encodes the enzyme that catalyzed the desaturation of oleate to linoleate.

Producing the omega‐3 fatty acids DHA and EPA in oilseed crops

AbstractThere is increasing consumer demand for the omega‐3 fatty acids docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) because of their well‐recognized benefits for human health and the observation that current western diets are deficient in these important polyunsaturated fatty acids (PUFAs). This has led to the need for additional cost‐effective and sustainable dietary sources of DHA and EPA beyond the traditional resource, oceanic fish. Recent advances in plant biotechnology have shown that DHA and EPA can be produced in vegetable oils using two approaches involving different sets of genes. One approach incorporates genes that direct sequential rounds of desaturation and elongation of native plant fatty acids. The other approach uses microalgal PUFA synthase genes to make DHA de novo without the need for native fatty acid precursors. These strategies offer the potential for sustainable production methods for DHA and EPA via land‐based oilseed crops.

Transgenic Biosynthesis of Polyunsaturated Fatty Acids: A Sustainable Biochemical Engineering Approach for Making Essential Fatty Acids in Plants and Animals

ADVERTISEMENT RETURN TO ISSUEPREVReviewNEXTTransgenic Biosynthesis of Polyunsaturated Fatty Acids: A Sustainable Biochemical Engineering Approach for Making Essential Fatty Acids in Plants and AnimalsJingjing Jiao† and Yu Zhang*‡View Author Information† Chronic Disease Research Institute, Department of Nutrition and Food Hygiene, School of Public Health, Zhejiang University, Hangzhou 310058, China‡ Department of Food Science and Nutrition, School of Biosystems Engineering and Food Science, Zhejiang University, Hangzhou 310058, China*E-mail: [email protected]Cite this: Chem. Rev. 2013, 113, 5, 3799–3814Publication Date (Web):February 19, 2013Publication History Received8 January 2012Published online19 February 2013Published inissue 8 May 2013https://doi.org/10.1021/cr300007pCopyright © 2013 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views1706Altmetric-Citations11LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit Read OnlinePDF (4 MB) Get e-AlertsSUBJECTS:Biosynthesis,Genetics,Lipidomics,Lipids,Peptides and proteins Get e-Alerts

Olive Oil Generated by the Recombinant <i>Escherichia coli</i> with ACCase Gene from <i>Jatropha curcas</i>

Acetyl-CoA carboxylase (ACCase) has a very important regulatory role in controlling plant fatty acid biosynthesis, thereby affecting lipid biosynthesis. The ACCase gene was amplified from Jatropha curcas using PCR with two degenerate primers, and the 1250-bp amplicon was cloned and sequenced. Sequence analysis revealed that the sequence obtained was similar to J atropha curcas , Ricinus communis , Camellia sinensis and Phaseolus vulgaris acetyl cocoa, with 75% similarity. The full length of the gene was sub-cloned into a prokaryotic expression vector and the induced recombinant Escherichia coli was grown on 0.2% (w/v) sodium oleate. The cell metabolite was analyzed using thin-layer chromatography and HPLC. This analysis revealed that the cell metabolite consisted of a mixture of esters, mainly consisting of oleic acid (0.7 g/L) plus minor amounts of palmitic acid, linoleic acid and stearic acid. Fed-batch cultivation of E. coli was conducted at the specific growth rates of 0.15 and 0.1 h -1 for constant and exponential strategies, respectively. A high cell density of 20 g/L with an overall biomass yield of 3 g/L was achieved.

Cloning and analysis of plant fatty acid desaturase 7 gene promoter from Brassica napus

In order to investigate the regulation mode of Brassica napus FAD7 gene in response of thermal stress, we measured the protein levels of BnFAD7 in plant at low and high temperature, and then analyzed promoter activity of 5’-flanking regions of BnFAD7 by transient gene expression in B. napus protoplasts at different temperatures. Our studies indicated that no significant change occurred in the expression level of BnFAD7 both at high and low temperature, while BnFAD7 promoter showed a heat-induced regulation mode and slowly increased activity at the chilling conditions, which suggested there are heat-induced cis-action element lies in BnFAD7 promoter sequence. Our data also suggested that a post-transcription regulation pattern existed to ensure BnFAD7 function in the acclimation to temperature stress. Furthermore, our studies give new evidence for the hypothesis that BnFAD7 and BnFAD8 gene may come from the same ancestor gene. Keywords: Brassica napus , fatty acids desaturase, promoter analysis, transient expression, BnFAD7

Molecular cloning and functional analysis of two FAD2 genes from American grape (Vitis labrusca L.)

The synthesis of polyunsaturated fatty acids (PUFAs), the most abundant fatty acids in plants, begins with a reaction catalyzed by fatty acid desaturase 2 (FAD2; EC 1.3.1.35), also called microsomal oleate Δ12-desaturase. Since the FAD2 gene was first identified in Arabidopsis thaliana, FAD2 research has gained wide interest as the essential enzyme for synthesizing PUFA. Grapes are one of the most frequently cultivated fruits in the world, with most commercial growers cultivating Vitis vinifera and V. labrusca. Grapeseed oil contains a high proportion, 60–70% of linoleic acid (18:2). We cloned two putative FAD2 genes from V. labrusca cv. Campbell Early based on V. vinifera genome sequences. Deduced amino acid sequences of two putative genes showed that VlFAD2s show high similarity to Arabidopsis FAD2 and commonly contain six transmembrane domain, three histidine boxes and endoplasmic reticulum (ER) retrieval motif representing the characteristics of fatty acid desaturase. Phylogenetic analyses of various plant FAD2s showed that VlFAD2-1 and VlFAD2-2 are separately grouped with constitutive and seed-type FAD2s, respectively. Southern blot showed that one or two bands are found in each lane. Because Campbell Early is a hybrid cultivar, FAD2-1 and FAD2-2 genes may exist as one copy in V. labrusca. Expression analysis in different tissues indicated that VlFAD2-1 is a constitutive gene but VlFAD2-2 is a seed-type gene. Complementation experiments of fad2-1 mutant Arabidopsis with VlFAD2-1 or VlFAD2-2 demonstrated that VlFAD2-1 and VlFAD2-2 can restore low PUFA proportion of fad2 to normal PUFA proportion.

인 결핍에 따른 하수배양 미세조류의 지방산 특성 분석 연구

하수에서 배양된 미세조류인 Chlorella vulgaris AG10032, Ankistrodesmus gracilis SAG278-2, Scenedesmus quadricauda AG10308은 오폐수에서 질소 및 인 제거가 우수하고 높은 지질을 함유하고 있어서, 오폐수에서 바이오연료나 기타 바이오 기반의 자원 회수에 유용한 생물자원이다. 오폐수 환경에는 다양한 인의 농도가 존재하는데, 인의 농도 특히 인 결핍조건에 따른 조류의 지방산 특성에 대한 정보가 매우 제한적이다. 이는 표준 분석방법이 정립되어 있지 않은데 일부 기인한다. 본 연구에서는 미생물의 지방산을 분석하는데 일반적으로 사용되는 무극성 컬럼법과 식물성 지질을 분석하는데 널리 사용되는 극성 WAX-type 컬럼 GC-FID 방법의 미세조류 지방산 분석 성능을 비교 분석하였고, 하수배양 조류에 적용이 보다 적절한 방법을 이용해서 인 결핍에 의한 조류 지방산 생성특성에 미치는 영향을 평가하였다. 그 결과 무극성 컬럼 방법에 비해 극성 WAX-type 컬럼 GC 방법이 <TEX>$C_{18:3}$</TEX> 지방산과 같은 고불포화지방산을 규명하는 분석능력이 우수하였고, 실제 하수배양에서 배양 분리된 미세조류의 지방산 분석에 보다 정확한 결과를 보이었다. 이 WAX-type 컬럼 방법으로 인 결핍 영향을 분석한 결과, 미세조류의 지방산 조성과 생성량은 인의 농도 변화에 크게 영향을 받지 않음을 밝히었다. Wastewater-adapted microalgae such as Chlorella vulgaris AG10032, Ankistrodesmus gracilis SAG278-2 and Scenedesmus quadricauda AG10308 are useful biological resources for recovering biofuel and other bio-based materials from wastewater because of their efficient removals of nitrogen and phosphorus from wastewater and their high fatty acid contents in biomass. Although the concentrations of phosphorus typically vary in wastewater environment, very little is known about the effect of phosphorus concentration, especially phosphorus starvation, on microalgal fatty acid synthesis. This is partially due to the lack of methodological establishment for algal fatty acid analysis. In this study, we compared the analysis performances of microalgal fatty acids by two different methods; one is a non-polar GC (gas chromatography) column based method, which is generally used for microbial fatty acids, and the other is a polar WAX-type GC column method, which is typically used for plant fatty acids. And then, we explored the effect of phosphorus concentration levels on fatty acid production in microalgae cultivated from wastewater. As results, the polar WAX-type column method has better ability to separate poly unsaturated fatty acids (PUFA) including <TEX>$C_{18:3}$</TEX> (linolenic acid), and was found to be more applicable in analyzing fatty acids from wastewater-cultivated microalgae than the non-polar column method. The fatty acid characterization by the WAX-type column method revealed little effect of phosphorus starvation on the quantity and composition of fatty acids from wastewater-cultivated microalgae.

THE PLANTS OF CRYOLITHOZONE AS PERSPECTIVE PRODUCERS OF BIOLOGICALLY ACTIVE SUBSTANCES

biogenic stimulants are substances produced under certain conditioner animal and plant tissue (4–8 °C in darkness for several days) and possessing biological activity. Similar processes of the formation of biologically active substances (bAS) — biostimulators, may occur in natural conditions, especially in the regions where plants experience long-term low temperature stress (cryolithic zone). The aim of our work was to study seasonal profiles of bAS accumulation of plant pigments (carotenoids, chlorophyll) and fatty acids (fA) of the plants of Central and North-Eastern yakutia. The following species were investigated: Pinus sylvestris, Picea obovata, Larix cajanderi, Betula platyphylla, Duschekia fruticosa, Equisetum variegatum, E. scirpoides, Psathyrostachys juncea, Elymus sibiricus, Elytrigia repens, Bromopsis inermis, Avena sativa, Hordium vulgare, Eriophorum vaginatum. Pigment identification was performed by thin-layer chromatography, fA of lipids — using column chromatography. it was found that under long cold hardening the plants of cryolithic zone, particularly evergreen species and permanent grasses, significantly accumulate bAS, compared to summer period: carotenoids (β-carotene, lutein, and other xanthophylls) and essential fA. in the conditions of sharply continental climate and permafrost, where there are no winter thawing, the aboveground organs of woody plants, first of all buds, needles, as well as grassy plants having gone under the snow in green state, durably preserve these substances. The plants of cryolithic zone may become a perspective source of bAS.

Microbial-Induced Carbon Competition in the Spermosphere Leads to Pathogen and Disease Suppression in a Municipal Biosolids Compost

The aim of this study was to understand whether competition for fatty acids in plant seed exudates by compost-derived seed-colonizing microbial communities could explain the suppression of plant infections initiated by sporangia of Pythium ultimum. The germination behavior of P. ultimum sporangia in response to cucumber seeds was measured to determine the impact of seed-colonizing microbes on pathogen suppression. Seed-colonizing microbial communities from municipal biosolids compost utilized cucumber seed exudates and linoleic acid in vitro, reducing the respective stimulatory activity of these elicitors to P. ultimum sporangial germination. However, when sporangia were observed directly in the spermosphere of seeds sown in the compost medium, levels of germination and sporangial emptying did not differ from the responses in sand. The percentage of aborted germ tubes was greater after incubating sporangia in compost medium for 12-h than the level of germ tube abortion when sporangia were incubated in sand. Abortion did not occur if previously germinated sporangia were supplemented with cucumber seed exudate. Furthermore, removal of cucumber seed exudate after various stages of germ tube emergence resulted in an increase in aborted germ tubes over time. Adding increasing levels of glucose directly to the compost medium alleviated germ tube abortion in the spermosphere and also eliminated disease suppression. These data fail to support a role for linoleic acid competition in Pythium seedling disease suppression but provide evidence for general carbon competition mediated by seed-colonizing microbial communities as a mechanism for the suppression of Pythium seed infections in municipal biosolids compost.

Biogeochemistry of near-bottom suspended particulate matter of the Beaufort Sea shelf (Arctic Ocean): C, N, P, δ 13C and fatty acids

The influence of the Mackenzie River on the source, composition, and distribution of dissolved nutrients and suspended particulate matter (SPM) in near-bottom waters on the Beaufort Sea shelf was determined by measuring particulate organic carbon (POC), particulate nitrogen (PN), particulate phosphorus (PP), elemental ratios (C:N, C:P, N:P), chlorophyll a, bulk δ13C, and fatty acids. The Mackenzie River had a strong influence on the composition of SPM in near-bottom waters across the entire Canadian Beaufort Sea shelf, including the Amundsen Gulf. This influence was strongest at stations near the river mouth and decreased offshore and northeastward towards the Amundsen Gulf, as seen in SPM elemental concentrations, δ13C, and terrestrial plant fatty acid markers. Low C:N ratios and high relative levels of odd-numbered carbon and branched-chained fatty acids (bacterial fatty acid markers) indicated that bacteria were an important contributor to organic matter at stations near the river and on the Mackenzie shelf. Fatty acid analysis allowed detection of a phytoplankton sinking event in the Amundsen Gulf in which polyunsaturated fatty acid (PUFA) levels in near-bottom waters significantly increased from June to July. However, this change in PUFA was not associated with any observed temporal change in chlorophyll a, δ13C, or C:N ratios. These results show that a multiple biomarker approach is necessary in ecosystem studies of dynamic environments such as near-bottom waters or river-influenced shelves.

Systematic Metabolic Engineering of ω-7 Fatty Acids in Plants

Systematic Metabolic Engineering of ω-7 Fatty Acids in Plants