Palmitic Content Research Articles

Yeast cells accumulate excess endogenous palmitate in phosphatidylcholine by acyl chain remodeling involving the phospholipase B Plb1p

In the yeast Saccharomyces cerevisiae, the molecular species profile of the major membrane glycerophospholipid phosphatidylcholine (PC) is determined by the molecular species-selectivity of the biosynthesis routes and by acyl chain remodeling. Overexpression of the glycerol-3-phosphate acyltransferase Sct1p was recently shown to induce a strong increase in the cellular content of palmitate (C16:0). Using stable isotope labeling and mass spectrometry, the present study shows that wild type yeast overexpressing Sct1p incorporates excess C16:0 into PC via the methylation of PE, the CDP-choline route, and post-synthetic acyl chain remodeling. Overexpression of Sct1p increased the extent of remodeling of PE-derived PC, providing a novel tool to perform mechanistic studies on PC acyl chain exchange. The exchange of acyl chains occurred at both the sn-1 and sn-2 positions of the glycerol backbone of PC, and required the phospholipase B Plb1p for optimal efficiency. Sct1p-catalyzed acyl chain exchange, the acyl-CoA binding protein Acb1p, the Plb1p homologue Plb2p, and the glycerophospholipid:triacylglycerol transacylase Lro1p were not required for PC remodeling. The results indicate that PC serves as a buffer for excess cellular C16:0.

Secretory Phospholipases A2 in Durum Wheat (Triticum durum Desf.): Gene Expression, Enzymatic Activity, and Relation to Drought Stress Adaptation

Phospholipases A2 (PLA2s) are known to mediate signaling cascades during plant growth and development, as well as biotic and abiotic stress responses. In this context, the present study provides extensive characterization of specific PLA2s in durum wheat, and assesses their involvement in durum wheat response to drought stress. In durum wheat leaves, four full-length expressed sequences encoding putative PLA2s were isolated and characterized as belonging to the class of secretory PLA2s (sPLA2s): TdsPLA2I, TdsPLA2II, TdsPLA2III and TdsPLA2IV. PLA2 activity was also detected, the characteristics of which resemble those of previously characterized plant sPLA2s: strong preference for phospholipids; requirement for millimolar Ca2+ concentrations; optimal activity at basic pH; heat stability; and inhibition by the reducing agent dithiothreitol. With drought stress imposed at both the vegetative and reproductive stages, accumulation of TdsPLA2I and TdsPLA2III transcripts, and to a lesser extent of TdsPLA2IV transcript, paralleled increased PLA2 activity; both transcript levels and enzymatic activity decreased as a consequence of stress recovery. Consistently, free fatty acid analysis of drought-stressed leaves revealed increased linoleate, linolenate and palmitate contents, which were reversed by plant re-watering. Overall, these findings strongly suggest that there are inducible sPLA2 isoforms in durum wheat that have roles in orchestrating the plant response to drought stress.

Binding of vitamin A by casein micelles in commercial skim milk

Recent studies have shown that reassembled micelles formed by caseinates and purified casein fractions (αs- and β-casein) bind to hydrophobic compounds, including curcumin, docosahexaenoic acid, and vitamin D. However, limited research has been done on the binding of hydrophobic compounds by unmodified casein micelles in skim milk. In the present study, we investigated the ability of casein micelles in commercial skim milk to associate with vitamin A (retinyl palmitate), a fat-soluble vitamin commonly used to fortify milk. Milk protein fractions from different commercially available skim milk samples subjected to different processing treatments, including pasteurized, ultrapasteurized, organic pasteurized, and organic ultrapasteurized milks, were separated by fast protein liquid chromatography. The fractions within each peak were combined and freeze-dried. Sodium dodecyl sulfate-PAGE with silver staining was used to identify the proteins present in each of the fractions. The skim milk samples and fractions were extracted for retinyl palmitate and quantified against a standard using normal phase-HPLC. Retinyl palmitate was found to associate with the fraction of skim milk containing caseins, whereas the other proteins (BSA, β-lactoglobulin, α-lactalbumin) did not show any binding. The retinyl palmitate content in the various samples ranged from 1.59 to 2.48µg of retinyl palmitate per mL of milk. The casein fractions contained between 14 and 40% of total retinyl palmitate in the various milks tested. The variation in the retention of vitamin A by caseins was probably explained by differences in the processing of different milk samples, including thermal treatment, the form of vitamin A emulsion used for fortification, and the point of fortification during processing. Unmodified casein micelles have a strong intrinsic affinity toward the binding of vitamin A used to fortify commercially available skim milks.

Fat-soluble vitamin (A, D, E, and β-carotene) contents from a Portuguese autochthonous cow breed—Minhota

In Portugal, commercial milk is obtained almost entirely from cows of the Holstein breed. However, other breeds may also show dairy aptitude, and produce milk of good quality. The aim of this study was to investigate the effect of the breed factor in the vitamin contents of milks from Holstein and the autochthonous Portuguese breed Minhota, as well as possible variations due to season. Milk samples were collected from 15 cows of each breed. Milk from Minhota cows showed higher contents of retinol, retinyl palmitate, α-tocopherol, and β-carotene. No differences were verified between breeds regarding vitamin D3 content, but Holstein cows presented higher amounts of provitamin D3. Seasonal variations were not observed for milk samples from Holsteins, and only a very small variation was observed for milk samples from Minhota cows, mainly in retinol, α-tocopherol, and provitamin D3 levels. This study revealed that breed has a pronounced effect on milk fat-soluble vitamins, which is an important observation regarding future genetic selection plans. Also, the increased vitamin amounts found in milk from Minhota cows can be regarded as an important nutritional parameter that can potentiate the economical value of this breed.

High Payload Dual Therapeutic‐Imaging Nanocarriers for Triggered Tumor Delivery

The in vitro and in vivo characterization of an optimized formulation of nanoparticles (NPs) loaded with a high content of dexamethasone palmitate (DEX-P), a chemotherapeutic adjuvant that decreases interstitial fluid pressure in tumors, and (111) In, a signaling agent, is described. These NPs are uniform in size and composition. Single photon emission computed tomography imaging demonstrates significant tumor uptake of (111) In-labeled DEX-P NPs in tumor-bearing mice. As with many nanoparticle-based drug delivery systems, significant liver accumulation is observed. Assessment of liver histology and blood tests show no apparent hepatic or renal toxicity of the DEX-P NPs. Conversion of DEX-P to DEX occurs when DEX-P NPs are incubated with mouse plasma, human tumor homogenate and ascites from tumor bearing mice, but not with human plasma. This conversion is slower in plasma from Es1(e) ((-/-)) /SCID mice, a potential alternative animal model that better mimics humans; however, plasma from these mice are not completely devoid of esterase activity. The difference between blood and tumor esterase activity in humans facilitates the delivery of DEX-P NPs to tumors and the release of dexamethasone by an esterase trigger.

Survey of SSC12 Regions Affecting Fatty Acid Composition of Intramuscular Fat Using High-Density SNP Data

Fatty acid composition is a critical aspect of pork because it affects sensorial and technological aspects of meat quality and it is relevant for human health. Previous studies identified significant QTLs in porcine chromosome 12 for fatty acid profile of back fat (BF) and intramuscular fat (IMF). In the present study, 374 SNPs mapped in SSC12 from the 60K Porcine SNP Beadchip were used. We have combined linkage and association analyses with expression data analysis in order to identify regions of SSC12 that could affect fatty acid composition of IMF in longissimus muscle. The QTL scan showed a region around the 60-cM position that significantly affects palmitic fatty acid and two related fatty acid indexes. The Iberian QTL allele increased the palmitic content (+2.6% of mean trait). This QTL does not match any of those reported in the previous study on fatty acid composition of BF, suggesting different genetic control acting at both tissues. The SNP association analyses showed significant associations with linolenic and palmitic acids besides several indexes. Among the polymorphisms that affect palmitic fatty acid and match the QTL region at 60 cM, there were three that mapped in the Phosphatidylcholine transfer protein (PCTP) gene and one in the Acetyl-CoA Carboxylase ∝ gene (ACACA). Interestingly one of the PCTP SNPs also affected significantly unsaturated and double bound indexes and the ratio between polyunsaturated/monounsaturated fatty acids. Differential expression was assessed on longissimus muscle conditional on the genotype of the QTL and on the most significant SNPs, according to the results obtained in the former analyses. Results from the microarray expression analyses, validated by RT-qPCR, showed that PCTP expression levels significantly vary depending on the QTL as well as on the own PCTP genotype. The results obtained with the different approaches point out the PCTP gene as a powerful candidate underlying the QTL for palmitic content.

Quantification of Vitamin A in Palm Oil Using a Fast and Simple Portable Device: Method Validation and Comparison to High-Performance Liquid Chromatography

Vitamin A deficiency continues to be a global public health problem. Fortification of oil with vitamin A is considered a cost-effective, feasible strategy to prevent this problem but quality control poses a challenge to program implementation. To overcome this, we have validated a newly developed device that quantitatively measures the content of retinyl palmitate in refined palm oil, is simple to use, and yields immediate results.Linearity of analysis ranged from 2.5 - 30 mg retinol equivalents (RE)/ kg of palm oil, with 2.5 mg RE/kg being the determination limit; inter- and intra-assay precision ranged from 1.4 - 7.1 %. Comparison with a high-performance liquid chromatography method showed high agreement between the methods (R(2) = 0.92; Limits of Agreement: -1.24 mg to 2.53 mg RE/kg), and further comparisons illustrate that the new device is useful in low-resource settings. This device offers a field- and user-friendly solution to quantifying the vitamin A content in refined palm oil.

Fructose‐induced increases in hepatic palmitate perturbs cell Ca2+ and UPR signaling

Fructose (F) is linked to the pathogenesis of fatty liver disease. We recently discovered that F increases levels of reactive oxygen species (ROS) in hepatocytes and that F consumption specifically increases total lipid and palmitate (P) content of the liver. Since P is relatively toxic, here we evaluated whether P by itself induces endoplasmic reticulum (ER) stress thereby altering cell Ca and the unfolded protein response (UPR) known to be associated with oxidative stress and inflammation of the liver. Primary rat hepatocytes exposed to 300 μM P (in BSA) displayed known biomarkers of ER stress by increases in expression of BiP and in splicing of XBP1 (XBP1s). The P-induced increases in BiP expression and XBP1s are prevented by apocynin and allopurinol, inhibitors of NADPH and xanthine oxidase, respectively, suggesting that P-induced ROS may contribute to the UPR following F-induced ER stress. In the presence of glucose, P had little effect on cytosolic Ca ([Ca2+]i) in hepatocytes loaded with fura-2/AM. In the presence of F, P significantly enhanced fructose-induced increases in [Ca2+]i, an effect that occurred in >80% of the cells. The addition of BSA alone did not alter [Ca2+]i. Thus, P can act synergistically with F to produce large amplitude [Ca2+]i spikes. Taken together, P does not induce [Ca2+]i spikes independent of F, but may directly affect the UPR (NIH R01AA017752 NSF IBN722365).

Increased Mitochondrial Fatty Acid Oxidation Is Sufficient to Protect Skeletal Muscle Cells from Palmitate-induced Apoptosis

The mechanisms underlying the protective effect of monounsaturated fatty acids (e.g. oleate) against the lipotoxic action of saturated fatty acids (e.g. palmitate) in skeletal muscle cells remain poorly understood. This study aimed to examine the role of mitochondrial long-chain fatty acid (LCFA) oxidation in mediating oleate's protective effect against palmitate-induced lipotoxicity. CPT1 (carnitine palmitoyltransferase 1), which is the key regulatory enzyme of mitochondrial LCFA oxidation, is inhibited by malonyl-CoA, an intermediate of lipogenesis. We showed that expression of a mutant form of CPT1 (CPT1mt), which is active but insensitive to malonyl-CoA inhibition, in C2C12 myotubes led to increased LCFA oxidation flux even in the presence of high concentrations of glucose and insulin. Furthermore, similar to preincubation with oleate, CPT1mt expression protected muscle cells from palmitate-induced apoptosis and insulin resistance by decreasing the content of deleterious palmitate derivates (i.e. diacylglycerols and ceramides). Oleate preincubation exerted its protective effect by two mechanisms: (i) in contrast to CPT1mt expression, oleate preincubation increased the channeling of palmitate toward triglycerides, as a result of enhanced diacylglycerol acyltransferase 2 expression, and (ii) oleate preincubation promoted palmitate oxidation through increasing CPT1 expression and modulating the activities of acetyl-CoA carboxylase and AMP-activated protein kinase. In conclusion, we demonstrated that targeting mitochondrial LCFA oxidation via CPT1mt expression leads to the same protective effect as oleate preincubation, providing strong evidence that redirecting palmitate metabolism toward oxidation is sufficient to protect against palmitate-induced lipotoxicity.

Acid Components in Arachis Species and Interspecies Hybrids with High Oleic and Low Palmitic Acids

Fatty acids of 87 wild Arachis accessions and 113 interspecific hybrid derivatives were tested to investigate their variations and breeding potential for improving fatty acid content in cultivated peanut ( A. hypogaea L.). Compared with cultivated peanut, the wild species showed similar palmitic content, lower stearic and oleic contents, and higher linoleic content. The components of fatty acids varied obviously across species or accessions in the same species. The lowest content of palmitic acid was in A. rigonii; the highest oleic acid content in A. pusilla and A. duranensis, and the highest linoleic acid content in A. batizoco. Two accessions coded as 19-6 ( A. duranensis) and 23-1 ( Arachis sp.) were identified with oleic content higher than 60%. Seven species were in high content of linoleic acid (>40%), including accession 11-4 ( A. rigonii) with 48% of linoleic acid content that was the highest record. The interspecific hybrids had transgressive segregation in most fatty acids. There were significant variations in contents of palmitic, stearic, oleic, and linoleic acids among the hybrid lines. Six hybrids were obtained with oleic acid content higher than 64% and palmitic acid content less than 8.5%, such as yz8913-8 with oleic acid content of 67.8% (30 percent points higher than its parents) and palmitic acid content of 7.6%. Analysis based on sequence-related amplified polymorphism (SRAP) showed that new bands were present in the 6 hybrids. According to pod yield per plant, hundred-pod weight, hundred-seed weight, growth duration, main stem height, and total branch number, hybrids yz8818-16, yz903-1-59, yz903-2-40, and y8913-8 were of great value in breeding programs.

Heritability of Oleic Acid Content in Soybean Seed Oil and Its Genetic Correlation with Fatty Acid and Agronomic Traits

Oleate content is important for the nutritional value and oxidative stability of soybean [Glycine max (L.) Merr.] seed oil. Response to selection for higher oleate content depends on its heritability in breeding populations, and correlated responses of other fatty acid and agronomic traits to selection for oleate content depend on their genetic correlations with oleate. The objective of this study was to estimate the heritability of oleate content and to determine the correlation of oleate with other fatty acid and agronomic traits in three soybean populations segregating for major and minor oleate genes grown in multiple environments. One of the populations consisted of 721 lines, providing excellent precision for estimation of the genetic parameters. The results of this study indicated that heritability for oleate content was sufficiently high that early generation selection can be effective when practiced on unreplicated lines grown at a single environment. Significant negative correlations were observed between oleate and linoleate, oleate and linolenate, as well as oleate and palmitate in all three populations. Significant positive correlations were detected between palmitate and stearate in one population segregating for oleate genes and fapnc and fap1 alleles, which reduce palmitate content. In the same population we also observed a significant negative correlation between yield and oleate content, and positive correlations between yield and linoleate, and linolenate and palmitate contents.

Dietary vitamin A concentration alters fatty acid composition in pigs

This experiment was conducted to study the effect of vitamin A concentration in the diet on fatty acid composition in pigs. One-hundred and twenty eight Duroc × (Large White × Landrace) castrated male pigs were used. Pigs were randomly distributed and located in cages of four pigs each to the following treatment: vitamin A-enriched diet (100,000 IU/kg) ( n = 16) and control diet with a basal level (7500 IU/kg) ( n = 16). The pigs were slaughtered at an average weight of 125.9 kg. No effect of diet vitamin A level on performance, carcass traits and intramuscular fat percentage was observed. The retinol concentration in subcutaneous backfat and retinol and retinol palmitate contents in liver were higher in the pigs that were given the vitamin A enriched diet than in those receiving the control diet. However the vitamin A supplementation did not increase the retinol content in the muscle. Pigs receiving the vitamin A enriched diet showed a higher C16:0 and ∑SFA proportions in the outer layer and C18:0 and ∑SFA proportions in the inner layer. Moreover, the diet rich in vitamin A led to a reduction of C18:1 n−9 and ∑MUFA proportions in subcutaneous backfat inner layer. Dietary vitamin A concentration had not influence on main fatty acids composition of intramuscular lipids. Dietary vitamin A enrichment lead to a higher C16:0, ∑SFA concentration in liver lipids.

Estimating the Individual Effects of the Reduced Palmitic Acid fapnc and fap1 Alleles on Agronomic Traits in Two Soybean Populations

Major fap alleles that reduce palmitate content in soybean [Glycine max (L.) Merr.] seed oil also can reduce seed yield. One of these alleles, fapnc, has been shown to be a deletion in the GmFATB1a gene. Allele‐specific primers that amplify GmFATB1a can be used to test precisely if the fapnc allele has an effect on agronomic traits. The objectives of this study were to determine if the segregation of the fapnc allele explained a significant amount of genetic variation in several agronomic traits; to determine if the fap1 allele or minor palmitate genes have an effect on agronomic traits; and to confirm if GmFATB1a maps to the distal region on linkage group A1. GmFATB1a‐specific primers were used to genotype lines from two populations segregating for fapnc, fap1, and fan alleles and modifier genes. The fapnc allele explained a significant portion of the genetic variation in seed yield, plant height, protein content, and stearic acid content in both populations. After removing the effect of fapnc from the model, the genetic correlation between palmitate and yield was significant in one population but not significant between palmitate and height, indicating that fap1 has a small but significant effect on seed yield but no effect on plant height. The fap1 and/or modifier genes significantly affected stearic acid content. GmFATB1a mapped 20 cM distal to Satt684 on linkage group A1. Breeding efforts did not totally eliminate the negative influence of the fapnc allele on seed yield and plant height.

The effect of cetyl palmitate crystallinity on physical properties of gamma-oryzanolencapsulated in solid lipid nanoparticles

This present study was aimed at investigating the effect of the crystallinity of cetylpalmitate based solid lipid nanoparticles (SLNs) on the physical properties ofγ-oryzanol-loaded SLNs. SLNs consisting of varying ratios of cetyl palmitate andγ-oryzanol were prepared. Their hydrodynamic diameters were inthe range 210–280 nm and the zeta potentials were in the range−27 to−35 mV. The size of SLNs increased as the amount of cetyl palmitate decreased whereas no significantchange of zeta potentials was found. Atomic force microscopy pictures indicated the presenceof disc-like particles. The crystallinity of SLNs, determined by differential scanning calorimetryand powder x-ray diffraction, was directly dependent on the ratio of cetyl palmitate toγ-oryzanol and decreased with decreasing cetyl palmitate content in the lipidmatrix. Varying this ratio in the lipid mix resulted in a shift in the meltingtemperature and enthalpy, although the SLN structure remained unchanged as anorthorhombic lamellar lattice. This has been attributed to a potential inhibition byγ-oryzanol during lipid crystal growth as well as a less ordered structure of the SLNs. Theresults revealed that the crystallinity of the SLNs was mainly dependent on the solid lipid,and that the crystallinity has an important impact on the physical characteristics ofactive-loaded SLNs.

Characterization and cloning of a stearoyl/oleoyl specific fatty acyl-acyl carrier protein thioesterase from the seeds of Madhuca longifolia ( latifolia)

Deposition of oleate, stearate and palmitate at the later stages of seed development in Mahua ( Madhuca longifolia ( latifolia)), a tropical non-conventional oil seed plant, has been found to be the characteristic feature of the regulatory mechanism that produces the saturated fatty acid rich Mahua seed fat (commonly known as Mowrah fat). Although, the content of palmitate has been observed to be higher than that of stearate at the initial stages of seed development, it goes down when the stearate and oleate contents consistently rise till maturity. The present study was undertaken in order to identify the kind of acyl-ACP thioesterase(s) that drives the characteristic composition of signature fatty acids (oleate 37%, palmitate 25%, stearate 23%, linoleate 12.5%) in its seed oil at maturity. The relative Fat activities in the crude protein extracts of the matured seeds towards three thioester substrates (oleoyl-, stearoyl- and palmitoyl-ACP) have been found to be present in the following respective ratio 100:31:8. Upon further purification of the crude extract, the search revealed the presence of two partially purified thioesterases: a long-chain oleoyl preferring house-keeping LC-Fat and a novel stearoyl-oleoyl preferring SO-Fat. The characteristic accumulation of oleate and linoleate in the M. latifolia seed fat is believed to be primarily due to the thioesterase activity of the LC-Fat or MlFatA. On the other hand, the SO-Fat showed almost equal substrate specificity towards stearoyl- and oleoyl-ACP, when its activity towards palmitoyl-ACP compared to stearoyl-ACP was only about 12%. An RT-PCR based technique for cloning of a DNA fragment from the mRNA pool of the developing seed followed by nucleotide sequencing resulted in the identification of a FatB type of thioesterase gene ( MlFatB). This gene was found to exist as a single copy in the mother plant genome. Ectopic expression of this MlFatB gene product in E. coli strain fadD88 further proved that it induced a higher level of accumulation of both stearic and oleic acids when compared to the negative control line that did not contain this MlFatB gene. It also indicated that SO-Fat indeed is the product of the MlFatB gene present in the maturing seeds of M. latifolia in nature. Additionally, a predicted 3D-structure for MlFatB protein has been developed through use of bioinformatics tools.

Correlations between Palmitate Content and Agronomic Traits in Soybean Populations Segregating for the fap1, fapnc, and fan Alleles

Palmitate is the predominant saturated fatty acid in soybean oil. Major fap alleles that reduce palmitate content in seed oil also reduce seed yield. Breeders are interested in estimating the genotypic correlation between palmitate content and agronomic traits to predict unfavorable correlated responses to selection. The main objective of this study was to estimate the genotypic and phenotypic correlations between palmitate and linolenate contents and other traits in three populations segregating for the fapnc, fap1, and fan alleles and modifier genes. The populations derived from crosses of high‐yielding lines and improved low‐palmitate and low‐linolenate lines were grown in replicated trials in three environments. Significant positive genetic correlations between palmitate and yield and between palmitate and plant height were observed in all three populations. Linolenate content was genetically positively correlated with lodging in two populations and negatively correlated with oil content in three populations. Our results support the observation that the major fapnc or fap1 or both alleles reduced plant height and had a major negative effect on yield. These effects could be due to pleiotropy or linkage with unfavorable yield or height genes. The relative importance of pleiotropy and linkage has very different implications for oil quality breeding.

Genetic Improvement of Seedling Emergence of Soybean Lines with Low Phytate

Seedling emergence of low‐phytate (LP) soybean [Glycine max (L.) Merr.] lines has been reported to be lower than that of normal‐phytate (NP) lines. One objective of this study was to evaluate if backcrossing the LP trait into a NP line would result in LP progeny with normal emergence. The LP line CX1834‐1‐6 (CX1834) was crossed to B01769B019 (B019), a NP line with reduced palmitate content, and three backcrosses were made to B019. A total of 36 BC3F4–derived LP lines from the population were evaluated at five locations in 2005 in comparison with CX1834, B019, and an NP cultivar IA3023. The mean phytate P and inorganic P content of all the backcross lines was not significantly different from CX1834. There were 18 backcross lines that had a mean field emergence that was significantly greater than CX1834 and not significantly different from B019. The results indicated that backcrossing seemed to be successful for developing LP lines with normal field emergence. A second objective of the study was to determine the effectiveness of warm germination, cold vigor, and accelerated aging tests for predicting field emergence of LP lines. Fifteen of the backcross lines were evaluated in the three tests that represented the range of field emergence that had been observed. The tests were useful for identifying lines with inferior field emergence but were not reliable enough to replace field tests for identifying the best emerging lines.

Molecular Analysis of Soybean Lines with Low Palmitic Acid Content in the Seed Oil

ABSTRACTPalmitic acid is the major saturated fatty acid found in soybean [Glycine max (L.) Merr.] oil, accounting for approximately 11% of the seed oil content. Reducing the palmitic acid levels of the oil is desirable because of the negative health effects specifically associated with this fatty acid. One of the genetic loci known to reduce the seed palmitate content in soybean is fapnc. Previous studies indicated that fapnc is associated with a deletion in a gene (designated FATB) encoding 16:0‐ACP thioesterase activity. In this report, we isolated full length cDNAs of three of the four unique FATB genes expressed in soybean and show that the isoform designated GmFATB1a represents the specific gene deleted in lines possessing the fapnc locus. Allele specific primers corresponding to GmFATB1a were used to genotype plants from two F4‐derived populations that were segregating for fapnc The GmFATB1a‐specific markers were effective in accounting for 62 to 70% of the genotypic variation in palmitate content in the two populations studied. Because the markers developed in this study are 100% linked to the locus of interest, they should be particularly useful in marker‐assisted selection programs designed to lower the palmitic acid levels of soybean oil.

A Mutation in a 3‐Keto‐Acyl‐ACP Synthase II Gene is Associated with Elevated Palmitic Acid Levels in Soybean Seeds

Palmitic acid is the major saturated fatty acid component of soybean [Glycine max (L.) Merr.] oil, typically accounting for approximately 11% of total seed oil content. Several genetic loci have been shown to control the seed palmitate content of soybean. One such locus, fap2, mediates an elevated seed palmitate phenotype. Previous biochemical studies indicated that the fap2 locus is associated with a reduction in the activity of 3‐keto‐acyl‐ACP synthase II (KAS II), an enzyme that initiates the elongation of palmitoyl‐ACP to stearoyl‐ACP in the plastid. The objective of the present research was to define the molecular basis by which the fap2 locus increases seed palmitate levels. We isolated two closely related, yet unique KAS II cDNAs, designated GmKAS IIA and GmKAS IIB, from soybean cultivar Century (Fap2, Fap2) and its derivative high palmitate germplasm C1727 (fap2, fap2). The GmKAS IIB cDNAs recovered from Century and C1727 were identical. In contrast, a single base‐pair substitution was found in the GmKAS IIA gene from C1727 versus Century which converted a tryptophan codon into a premature stop codon, a mutation that would be predicted to render the encoded enzyme nonfunctional. Knowledge of the DNA sequence polymorphism led to the development a facile, robust cleavage amplified polymorphic sequence (CAPS) marker that readily distinguishes the mutant GmKAS IIA gene. This marker faithfully associated with a second independent germplasm line bearing the fap2 locus, and thus may be useful in breeding programs that target the development of high palmitate soybean cultivars.

HPLC Quantification of Sphingolipids in Soybeans with Modified Palmitate Content

Efficient separation and accurate quantification of sphingolipids (SL) are important for studying SL concentrations and biological functions. The objectives of this study were to develop effective methods for the separation and quantification of SL and to determine the relationship between palmitate and SL contents of mature soybean seeds. Methods using column chromatography and high-performance liquid chromatography-evaporative light scattering detector (HPLC-ELSD) were developed to separate and quantify glucosylceramide (GlcCer) and ceramide (Cer) in 15 soybeans lines in which palmitate content ranged from 3.7 to 40.7%. There were significant differences among the lines for GlcCer (83.4-397.6 nmol/g) and major Cer contents (8.4-20.7 nmol/g) on a dry weight basis. The correlations of palmitate content with GlcCer and Cer concentrations were not significant. The results indicated that the palmitate content of soybean seed did not affect their GlcCer and Cer contents. Genetic factors other than those that control palmitate content seemed to be responsible for the variation among soybean lines for GlcCer and Cer contents.