Publications by authors named "Edgar B Cahoon"

108 Publications

Disruption of long-chain base hydroxylation alters growth and impacts sphingolipid synthesis in .

Plant Direct 2021 Jul 16;5(7):e336. Epub 2021 Jul 16.

Department of Biology Williams College Williamstown MA USA.

Sphingolipids have roles as membrane structural components and as bioactive molecules in plants. In , 4-hydroxysphinganine (phytosphingosine, t18:0) is the predominant sphingolipid long-chain base (LCB). To assess the functional significance of t18:0, CRISPR-Cas9 mutagenesis was used to generate mutant lines lacking the sole () gene encoding the hydroxylase responsible for converting sphinganine (d18:0) to t18:0. Total sphingolipid content in protonemata was 2.4-fold higher than in wild-type. Modest changes in glycosyl inositolphosphorylceramide (GIPC) glycosylation patterns occurred. Sphingolipidomic analyses of mutants lacking t18:0 indicated modest alterations in acyl-chain pairing with d18:0 in GIPCs and ceramides, but dramatic alterations in acyl-chain pairing in glucosylceramides, in which 4,8-sphingadienine (d18:2) was the principal LCB. A striking accumulation of free and phosphorylated LCBs accompanied loss of the hydroxylase. The lines exhibited altered morphology, including smaller chloronemal cell size, irregular cell shape, reduced gametophore size, and increased pigmentation. In the presence of the synthetic trihydroxy LCB t17:0, the endogenous sphingolipid content of lines decreased to wild-type levels, and the mutants exhibited phenotypes more similar to wild-type plants. These results demonstrate the importance of sphingolipid content and composition to Physcomitrella growth. They also illuminate similarities in regulating sphingolipid content but differences in regulating sphingolipid species composition between the bryophyte and angiosperm .
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http://dx.doi.org/10.1002/pld3.336DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8320657PMC
July 2021

Quantitative Trait Loci Controlling Agronomic and Biochemical Traits in Cannabis sativa.

Genetics 2021 Jun 26. Epub 2021 Jun 26.

Department of Agricultural Biology, Colorado State University, Fort Collins, Colorado, 80523, United States of America.

Understanding the genetic basis of complex traits is a fundamental goal of evolutionary genetics. Yet, the genetics controlling complex traits in many important species such as hemp (Cannabis sativa) remain poorly investigated. Since hemp's change in legal status with the 2014 and 2018 U.S. Federal Farm Bills, interest in the genetics controlling its numerous agriculturally important traits has steadily increased. To better understand the genetics of agriculturally important traits in hemp, we developed an F2 population by crossing two phenotypically distinct hemp cultivars (Carmagnola and USO31). Using whole genome sequencing, we mapped quantitative trait loci (QTL) associated with variation in numerous agronomic and biochemical traits. A total of 69 loci associated with agronomic (34) and biochemical (35) trait variation were identified. We found that most QTL co-localized, suggesting that the phenotypic distinctions between Carmagnola and USO31 are largely controlled by a small number of loci. We identified TINY and olivetol synthase as candidate genes underlying co-localized QTL clusters for agronomic and biochemical traits respectively. We functionally validated the olivetol synthase candidate by expressing the alleles in yeast. Gas chromatography-mass spectrometry assays of extracts from these yeast colonies suggest that the USO31 olivetol synthase is functionally less active and potentially explains why USO31 produces lower cannabinoids compared to Carmagnola. Overall, our results help modernize the genomic understanding of complex traits in hemp.
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http://dx.doi.org/10.1093/genetics/iyab099DOI Listing
June 2021

Genetic Engineering of Lesquerella with Increased Ricinoleic Acid Content in Seed Oil.

Plants (Basel) 2021 May 29;10(6). Epub 2021 May 29.

Department of Biochemistry and Center for Plant Science Innovation, University of Nebraska-Lincoln, Lincoln, NE 68588, USA.

Seeds of castor () are enriched in oil with high levels of the industrially valuable fatty acid ricinoleic acid (18:1OH), but production of this plant is limited because of the cooccurrence of the ricin toxin in its seeds. Lesquerella () is being developed as an alternative industrial oilseed because its seeds accumulate lesquerolic acid (20:1OH), an elongated form of 18:1OH in seed oil which lacks toxins. Synthesis of 20:1OH is through elongation of 18:1OH by a lesquerella elongase, PfKCS18. Oleic acid (18:1) is the substrate for 18:1OH synthesis, but it is also used by fatty acid desaturase 2 (FAD2) and FAD3 to sequentially produce linoleic and linolenic acids. To develop lesquerella that produces 18:1OH-rich seed oils such as castor, RNA interference sequences targeting , and were introduced to lesquerella to suppress the elongation and desaturation steps. Seeds from transgenic lines had increased 18:1OH to 1.1-26.6% compared with that of 0.4-0.6% in wild-type (WT) seeds. Multiple lines had reduced 18:1OH levels in the T generation, including a top line with 18:1OH reduced from 26.7% to 19%. Transgenic lines also accumulated more 18:1 than that of WT, indicating that 18:1 is not efficiently used for 18:1OH synthesis and accumulation. Factors limiting 18:1OH accumulation and new targets for further increasing 18:1OH production are discussed. Our results provide insights into complex mechanisms of oil biosynthesis in lesquerella and show the biotechnological potential to tailor lesquerella seeds to produce castor-like industrial oil functionality.
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http://dx.doi.org/10.3390/plants10061093DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8230273PMC
May 2021

Mass Spectrometry-Based Profiling of Plant Sphingolipids from Typical and Aberrant Metabolism.

Methods Mol Biol 2021 ;2295:157-177

Department of Biochemistry and Center for Plant Science Innovation, University of Nebraska-Lincoln, Lincoln, NE, USA.

Mass spectrometry has increasingly been used as a tool to complement studies of sphingolipid metabolism and biological functions in plants and other eukaryotes. Mass spectrometry is now essential for comprehensive sphingolipid analytical profiling because of the huge diversity of sphingolipid classes and molecular species in eukaryotes, particularly in plants. This structural diversity arises from large differences in polar head group glycosylation as well as carbon-chain lengths of fatty acids and desaturation and hydroxylation patterns of fatty acids and long-chain bases that together comprise the ceramide hydrophobic backbone of glycosphingolipids. The standard methods for liquid chromatography-mass spectrometry (LC-MS)-based analyses of Arabidopsis thaliana leaf sphingolipids profile >200 molecular species of four sphingolipid classes and free long-chain bases and their phosphorylated forms. While these methods have proven valuable for A. thaliana based sphingolipid research, we have recently adapted them for use with ultraperformance liquid chromatography separations of molecular species and to profile aberrant sphingolipid forms in pollen, transgenic lines, and mutants. This chapter provides updates to standard methods for LC-MS profiling of A. thaliana sphingolipids to expand the utility of mass spectrometry for plant sphingolipid research.
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http://dx.doi.org/10.1007/978-1-0716-1362-7_10DOI Listing
June 2021

CRISPR/Cas9-Induced and Mutations Stacked With Confer High Oleic Acid Seed Oil in Pennycress ( L.).

Front Plant Sci 2021 22;12:652319. Epub 2021 Apr 22.

School of Biological Sciences, Illinois State University, Normal, IL, United States.

Pennycress ( L.) is being domesticated as an oilseed cash cover crop to be grown in the off-season throughout temperate regions of the world. With its diploid genome and ease of directed mutagenesis using molecular approaches, pennycress seed oil composition can be rapidly tailored for a plethora of food, feed, oleochemical and fuel uses. Here, we utilized Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Cas9 technology to produce knockout mutations in the () and () genes to increase oleic acid content. High oleic acid (18:1) oil is valued for its oxidative stability that is superior to the polyunsaturated fatty acids (PUFAs) linoleic (18:2) and linolenic (18:3), and better cold flow properties than the very long chain fatty acid (VLCFA) erucic (22:1). When combined with a () knockout mutation, and double mutants produced ∼90% and ∼60% oleic acid in seed oil, respectively, with PUFAs in as well as single mutants reduced to less than 5%. MALDI-MS spatial imaging analyses of phosphatidylcholine (PC) and triacylglycerol (TAG) molecular species in wild-type pennycress embryo sections from mature seeds revealed that erucic acid is highly enriched in cotyledons which serve as storage organs, suggestive of a role in providing energy for the germinating seedling. In contrast, PUFA-containing TAGs are enriched in the embryonic axis, which may be utilized for cellular membrane expansion during seed germination and seedling emergence. Under standard growth chamber conditions, plants grew like wild type whereas single and double mutant plants exhibited delayed growth and overall reduced heights and seed yields, suggesting that reducing PUFAs below a threshold in pennycress had negative physiological effects. Taken together, our results suggest that combinatorial knockout of and may be a viable route to commercially increase oleic acid content in pennycress seed oil whereas mutations in will likely require at least partial function to avoid fitness trade-offs.
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http://dx.doi.org/10.3389/fpls.2021.652319DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8100250PMC
April 2021

A co-opted steroid synthesis gene, maintained in sorghum but not maize, is associated with a divergence in leaf wax chemistry.

Proc Natl Acad Sci U S A 2021 03;118(12)

Department of Biochemistry, University of Nebraska-Lincoln, Lincoln, NE 68588;

Virtually all land plants are coated in a cuticle, a waxy polyester that prevents nonstomatal water loss and is important for heat and drought tolerance. Here, we describe a likely genetic basis for a divergence in cuticular wax chemistry between , a drought tolerant crop widely cultivated in hot climates, and its close relative (maize). Combining chemical analyses, heterologous expression, and comparative genomics, we reveal that: 1) sorghum and maize leaf waxes are similar at the juvenile stage but, after the juvenile-to-adult transition, sorghum leaf waxes are rich in triterpenoids that are absent from maize; 2) biosynthesis of the majority of sorghum leaf triterpenoids is mediated by a gene that maize and sorghum both inherited from a common ancestor but that is only functionally maintained in sorghum; and 3) sorghum leaf triterpenoids accumulate in a spatial pattern that was previously shown to strengthen the cuticle and decrease water loss at high temperatures. These findings uncover the possibility for resurrection of a cuticular triterpenoid-synthesizing gene in maize that could create a more heat-tolerant water barrier on the plant's leaf surfaces. They also provide a fundamental understanding of sorghum leaf waxes that will inform efforts to divert surface carbon to intracellular storage for bioenergy and bioproduct innovations.
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http://dx.doi.org/10.1073/pnas.2022982118DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8000359PMC
March 2021

Plasma and Vacuolar Membrane Sphingolipidomes: Composition and Insights on The Role of Main Molecular Species.

Plant Physiol 2021 Feb 11. Epub 2021 Feb 11.

Dpto. de Bioquímica, Facultad de Química, Conj. E. Universidad Nacional Autónoma de México, UNAM. Cd. Universitaria, Coyoacán. 04510, Cd. de México. México.

Lipid structures affect membrane biophysical properties such as thickness, stability, permeability, curvature, fluidity, asymmetry, and interdigitation, contributing to membrane function. Sphingolipids are abundant in plant endomembranes and plasma membranes (PM) and comprise four classes: ceramides, hydroxyceramides, glucosylceramides, and glycosylinositolphosphoceramides (GIPCs). They comprise an array of chemical structures whose distribution in plant membranes is unknown. With the aim of describing the hydrophobic portion of sphingolipids, 18 preparations from microsomal (MIC), vacuolar (VM), PM, and detergent-resistant membranes (DRM) were isolated from Arabidopsis (Arabidopsis thaliana) leaves. Sphingolipid species, comprising pairing of long-chain bases and fatty acids, were identified and quantified in these membranes. Sphingolipid concentrations were compared using univariate and multivariate analysis to assess sphingolipid diversity, abundance, and predominance across membranes. The four sphingolipid classes were present at different levels in each membrane: VM was enriched in glucosylceramides, hydroxyceramides, and GIPCs; PMs in GIPCs, in agreement with their key role in signal recognition and sensing; and DRM in GIPCs, as reported by their function in nanodomain formation. While a total of 84 sphingolipid species was identified in MIC, VM, PM, and DRM, only 34 were selectively distributed in the four membrane types. Conversely, every membrane contained a different number of predominant species (11 in VM, 6 in PM, and 17 in DRM). This study reveals that MIC, VM, PM, and DRM contain the same set of sphingolipid species but every membrane source contains its own specific assortment based on the proportion of sphingolipid classes and on the predominance of individual species.
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http://dx.doi.org/10.1093/plphys/kiab064DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8154057PMC
February 2021

Dissecting the regulatory roles of ORM proteins in the sphingolipid pathway of plants.

PLoS Comput Biol 2021 01 28;17(1):e1008284. Epub 2021 Jan 28.

Department of Chemical and Biomolecular Engineering, University of Nebraska-Lincoln, Lincoln, Nebraska, United States of America.

Sphingolipids are a vital component of plant cellular endomembranes and carry out multiple functional and regulatory roles. Different sphingolipid species confer rigidity to the membrane structure, facilitate trafficking of secretory proteins, and initiate programmed cell death. Although the regulation of the sphingolipid pathway is yet to be uncovered, increasing evidence has pointed to orosomucoid proteins (ORMs) playing a major regulatory role and potentially interacting with a number of components in the pathway, including both enzymes and sphingolipids. However, experimental exploration of new regulatory interactions is time consuming and often infeasible. In this work, a computational approach was taken to address this challenge. A metabolic network of the sphingolipid pathway in plants was reconstructed. The steady-state rates of reactions in the network were then determined through measurements of growth and cellular composition of the different sphingolipids in Arabidopsis seedlings. The Ensemble modeling framework was modified to accurately account for activation mechanisms and subsequently used to generate sets of kinetic parameters that converge to the measured steady-state fluxes in a thermodynamically consistent manner. In addition, the framework was appended with an additional module to automate screening the parameters and to output models consistent with previously reported network responses to different perturbations. By analyzing the network's response in the presence of different combinations of regulatory mechanisms, the model captured the experimentally observed repressive effect of ORMs on serine palmitoyltransferase (SPT). Furthermore, predictions point to a second regulatory role of ORM proteins, namely as an activator of class II (or LOH1 and LOH3) ceramide synthases. This activating role was found to be modulated by the concentration of free ceramides, where an accumulation of these sphingolipid species dampened the activating effect of ORMs on ceramide synthase. The predictions pave the way for future guided experiments and have implications in engineering crops with higher biotic stress tolerance.
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http://dx.doi.org/10.1371/journal.pcbi.1008284DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7872301PMC
January 2021

Production of tocotrienols in seeds of cotton (Gossypium hirsutum L.) enhances oxidative stability and offers nutraceutical potential.

Plant Biotechnol J 2021 06 17;19(6):1268-1282. Epub 2021 Feb 17.

Department of Biological Sciences, BioDiscovery Institute, University of North Texas, Denton, TX, USA.

Upland cotton (Gossypium hirsutum L.) is an economically important multi-purpose crop cultivated globally for fibre, seed oil and protein. Cottonseed oil also is naturally rich in vitamin E components (collectively known as tocochromanols), with α- and γ-tocopherols comprising nearly all of the vitamin E components. By contrast, cottonseeds have little or no tocotrienols, tocochromanols with a wide range of health benefits. Here, we generated transgenic cotton lines expressing the barley (Hordeum vulgare) homogentisate geranylgeranyl transferase coding sequence under the control of the Brassica napus seed-specific promoter, napin. Transgenic cottonseeds had ~twofold to threefold increases in the accumulation of total vitamin E (tocopherols + tocotrienols), with more than 60% γ-tocotrienol. Matrix assisted laser desorption ionization-mass spectrometry imaging showed that γ-tocotrienol was localized throughout the transgenic embryos. In contrast, the native tocopherols were distributed unequally in both transgenic and non-transgenic embryos. α- Tocopherol was restricted mostly to cotyledon tissues and γ-tocopherol was more enriched in the embryonic axis tissues. Production of tocotrienols in cotton embryos had no negative impact on plant performance or yield of other important seed constituents including fibre, oil and protein. Advanced generations of two transgenic events were field grown, and extracts of transgenic seeds showed increased antioxidant activity relative to extracts from non-transgenic seeds. Furthermore, refined cottonseed oil from the two transgenic events showed 30% improvement in oxidative stability relative to the non-transgenic cottonseed oil. Taken together, these materials may provide new opportunities for cottonseed co-products with enhanced vitamin E profile for improved shelf life and nutrition.
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http://dx.doi.org/10.1111/pbi.13557DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8196643PMC
June 2021

Biotechnology tools and applications for development of oilseed crops with healthy vegetable oils.

Biochimie 2020 Nov 1;178:4-14. Epub 2020 Oct 1.

Center for Plant Science Innovation and Department of Biochemistry, University of Nebraska-Lincoln, Lincoln, NE, 68588, USA. Electronic address:

Vegetable oils, consisting principally of triacylglycerols (TAG), are major sources of calories and essential fatty acids in the human diet. The fatty acid composition of TAG is a primary determinant of the nutritional quality and health-promoting properties of vegetable oils. TAG fatty acid composition also affects the functionality and properties of vegetable oils in food applications and in food processing and preparation. Vegetable oils with improved nutritional and functional properties have been developed for oilseed crops by selection and breeding of fatty acid biosynthetic mutants. These efforts have been effective at generating vegetable oils with altered relative amounts of saturated and unsaturated fatty acids in seed TAG, but are constrained by insufficient genetic diversity for producing oils with "healthy" fatty acids that are not typically found in major oilseeds. The development and application of biotechnological tools have instead enabled the generation of oilseeds that produce novel fatty acid compositions with improved nutritional value by the introduction of genes from alternative sources, including plants, bacteria, and fungi. These tools have also allowed the generation of desired oil compositions that have proven difficult to obtain by breeding without compromised performance in selected oilseed crops. Here, we review biotechnological tools for increasing crop genetic diversity and their application for commercial or proof-of-principal development of oilseeds with expanded utility for food and feed applications and higher value nutritional and nutraceutical markets.
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http://dx.doi.org/10.1016/j.biochi.2020.09.020DOI Listing
November 2020

Stearidonic-Enriched Soybean Oil Modulates Obesity, Glucose Metabolism, and Fatty Acid Profiles Independently of Akkermansia muciniphila.

Mol Nutr Food Res 2020 09 26;64(17):e2000162. Epub 2020 Jul 26.

Department of Food Science and Technology, University of Nebraska-Lincoln, Lincoln, NE, 68588, USA.

Scope: Previous studies have suggested that diets rich in omega-3 and low in omega-6 long-chain polyunsaturated fatty acids (PUFAs) can limit the development of metabolic syndrome (MetS). Transgenic soybeans yielding oils enriched for omega-3 PUFAs represent a new and readily-available option for incorporating omega-3 PUFAs into diets to provide health benefits.

Methods And Results: Transgenic soybean oils, enriched for either stearidonic acid (SDA) or eicosapentaenoic acid (EPA), are incorporated into diets to test their effects on limiting the development of MetS in a mouse model of diet-induced obesity. Supplementation with SDA- but not EPA-enriched oils improved features of MetS compared to feeding a control wild-type oil. Because previous studies have linked the gut microorganism Akkermansia muciniphila to the metabolic effects of feeding omega-3 PUFAs, the causal contribution of A. muciniphila to mediating the metabolic benefits provided by SDA-enriched diets is investigated. Although A. muciniphila is not required for SDA-induced metabolic improvements, this microorganism does modulate levels of saturated and mono-unsaturated fatty acids in host adipose tissues.

Conclusion: Together, these findings support the utilization of SDA-enriched diets to modulate weight gain, glucose metabolism, and fatty acid profiles of liver and adipose tissue.
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http://dx.doi.org/10.1002/mnfr.202000162DOI Listing
September 2020

Unregulated Sphingolipid Biosynthesis in Gene-Edited Arabidopsis Mutants Results in Nonviable Seeds with Strongly Reduced Oil Content.

Plant Cell 2020 08 11;32(8):2474-2490. Epub 2020 Jun 11.

Center for Plant Science Innovation and Department of Biochemistry, University of Nebraska-Lincoln, Lincoln, Nebraska 68588

Orosomucoid-like proteins (ORMs) interact with serine palmitoyltransferase (SPT) to negatively regulate sphingolipid biosynthesis, a reversible process critical for balancing the intracellular sphingolipid levels needed for growth and programmed cell death. Here, we show that ORM1 and ORM2 are essential for life cycle completion in Arabidopsis (). Seeds from mutants, generated by crossing CRISPR/Cas9 knockout mutants for each gene, accumulated high levels of ceramide, indicative of unregulated sphingolipid biosynthesis. seeds were nonviable, displayed aberrant embryo development, and had >80% reduced oil content versus wild-type seeds. This phenotype was mimicked in Arabidopsis seeds expressing the SPT subunit LCB1 lacking its first transmembrane domain, which is critical for ORM-mediated regulation of SPT. We identified a mutant for ORM1 lacking one amino acid (Met-51) near its second transmembrane domain that retained its membrane topology. Expressing this allele in the background yielded plants that did not advance beyond the seedling stage, hyperaccumulated ceramides, and showed altered organellar structures and increased senescence- and pathogenesis-related gene expression. These seedlings also showed upregulated expression of genes for sphingolipid catabolic enzymes, pointing to additional mechanisms for maintaining sphingolipid homeostasis. ORM1 lacking Met-51 had strongly impaired interactions with LCB1 in a yeast () model, providing structural clues about regulatory interactions between ORM and SPT.
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http://dx.doi.org/10.1105/tpc.20.00015DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7401009PMC
August 2020

RGPDB: database of root-associated genes and promoters in maize, soybean, and sorghum.

Database (Oxford) 2020 01;2020

School of Biological Sciences, University of Nebraska, Lincoln, NE 68588 USA.

Root-associated genes play an important role in plants. Despite the fact that there have been studies on root biology, information on genes that are specifically expressed or upregulated in roots is poorly collected. There exist very few databases dedicated to genes and promoters associated with root biology, preventing effective root-related studies. Therefore, we analyzed multiple types of omics data to identify root-associated genes in maize, soybean, and sorghum and constructed a comprehensive online database of these genes and their promoter sequences. This database creates a pivotal platform capable of stimulating and facilitating further studies on manipulating root growth and development.
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http://dx.doi.org/10.1093/database/baaa038DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7273057PMC
January 2020

Plant unusual fatty acids: learning from the less common.

Curr Opin Plant Biol 2020 06 15;55:66-73. Epub 2020 Apr 15.

Aix Marseille Univ, CEA, CNRS, BIAM, Institut de Biosciences et Biotechnologies Aix-Marseille, CEA Cadarache, 13108 Saint Paul-Lez-Durance, France. Electronic address:

The plant kingdom contains an abundance of structurally diverse fatty acids referred to as unusual fatty acids. Unusual fatty acids on plant surfaces can form polyesters that contribute to the function of cutin as a barrier for water loss and pathogen protection. Unusual fatty acids are also found as abundant components of seed oils of selected species and often confer desirable properties for industrial and nutritional applications. Here, we review recent findings on the biosynthesis and metabolism of unusual fatty acids in cutin and seed oils and use of this information for enzyme structure-function studies and seed oil metabolic engineering. We also highlight the recent discovery of unusual fatty acids that are formed from a previously undescribed variation of fatty acid elongation.
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http://dx.doi.org/10.1016/j.pbi.2020.03.007DOI Listing
June 2020

The genome evolution and domestication of tropical fruit mango.

Genome Biol 2020 03 6;21(1):60. Epub 2020 Mar 6.

Tropical Crops Genetic Resources Institute, Chinese Academy of Tropical Agricultural Sciences & Ministry of Agriculture Key Laboratory of Crop Gene Resources and Germplasm Enhancement in Southern China, No. 4 Xueyuan Road, Haikou, 571100, Hainan, China.

Background: Mango is one of the world's most important tropical fruits. It belongs to the family Anacardiaceae, which includes several other economically important species, notably cashew, sumac and pistachio from other genera. Many species in this family produce family-specific urushiols and related phenols, which can induce contact dermatitis.

Results: We generate a chromosome-scale genome assembly of mango, providing a reference genome for the Anacardiaceae family. Our results indicate the occurrence of a recent whole-genome duplication (WGD) event in mango. Duplicated genes preferentially retained include photosynthetic, photorespiration, and lipid metabolic genes that may have provided adaptive advantages to sharp historical decreases in atmospheric carbon dioxide and global temperatures. A notable example of an extended gene family is the chalcone synthase (CHS) family of genes, and particular genes in this family show universally higher expression in peels than in flesh, likely for the biosynthesis of urushiols and related phenols. Genome resequencing reveals two distinct groups of mango varieties, with commercial varieties clustered with India germplasms and demonstrating allelic admixture, and indigenous varieties from Southeast Asia in the second group. Landraces indigenous in China formed distinct clades, and some showed admixture in genomes.

Conclusions: Analysis of chromosome-scale mango genome sequences reveals photosynthesis and lipid metabolism are preferentially retained after a recent WGD event, and expansion of CHS genes is likely associated with urushiol biosynthesis in mango. Genome resequencing clarifies two groups of mango varieties, discovers allelic admixture in commercial varieties, and shows distinct genetic background of landraces.
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http://dx.doi.org/10.1186/s13059-020-01959-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7059373PMC
March 2020

Palmitvaccenic Acid (Δ11--hexadecenoic acid) Is Synthesized by an OLE1-like Desaturase in the Arbuscular Mycorrhiza Fungus .

Biochemistry 2020 03 12;59(11):1163-1172. Epub 2020 Mar 12.

Institute of Molecular Physiology and Biotechnology of Plants (IMBIO), University of Bonn, Karlrobert-Kreiten-Straße 13, 53115 Bonn, Germany.

Arbuscular mycorrhiza (AM) fungi deliver mineral nutrients to the plant host in exchange for reduced carbon in the form of sugars and lipids. Colonization with AM fungi upregulates a specific host lipid synthesis pathway resulting in the production of fatty acids. Predominantly palmitic acid (16:0) and the unusual palmitvaccenic acid (16:1) accumulate in the fungus . Here, we present the isolation and characterization of OLE1-LIKE, the desaturase involved in palmitvaccenic acid synthesis, by heterologous expression in yeast and plants. Results are in line with the scenario in which encodes an acyl-CoA desaturase with substrate specificity for C15-C18 acyl groups, in particular C16. Phylogenetic analysis of -related sequences revealed that this gene is conserved in AM fungi from the Glomales and Diversisporales but is absent from nonsymbiotic Mortierellaceae and Mucoromycotina fungi, suggesting that 16:1 provides a specific function during AM colonization.
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http://dx.doi.org/10.1021/acs.biochem.0c00051DOI Listing
March 2020

The Lipid Flippases ALA4 and ALA5 Play Critical Roles in Cell Expansion and Plant Growth.

Plant Physiol 2020 04 12;182(4):2111-2125. Epub 2020 Feb 12.

Department of Biochemistry and Molecular Biology, University of Nevada at Reno, Reno, Nevada 89557

Aminophospholipid ATPases (ALAs) are lipid flippases involved in transporting specific lipids across membrane bilayers. Arabidopsis () contains 12 ALAs in five phylogenetic clusters, including four in cluster 3 (ALA4-ALA7). / and /, are expressed primarily in vegetative tissues and pollen, respectively. Previously, a double knockout of / was shown to result in pollen fertility defects. Here we show that a double knockout of / results in dwarfism, characterized by reduced growth in rosettes (6.5-fold), roots (4.3-fold), bolts (4.5-fold), and hypocotyls (2-fold). Reduced cell size was observed for multiple vegetative cell types, suggesting a role for ALA4/5 in cellular expansion. Members of the third ALA cluster are at least partially interchangeable, as transgenes expressing in vegetative tissues partially rescued mutant phenotypes, and expression of transgenes in pollen fully rescued mutant fertility defects. ALA4-GFP displayed plasma membrane and endomembrane localization patterns when imaged in both guard cells and pollen. Lipid profiling revealed rosettes had perturbations in glycerolipid and sphingolipid content. Assays in yeast revealed that ALA5 can flip a variety of glycerolipids and the sphingolipid sphingomyelin across membranes. These results support a model whereby the flippase activity of ALA4 and ALA5 impacts the homeostasis of both glycerolipids and sphingolipids and is important for cellular expansion during vegetative growth.
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http://dx.doi.org/10.1104/pp.19.01332DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7140935PMC
April 2020

Oil crops for the future.

Curr Opin Plant Biol 2020 08 23;56:181-189. Epub 2020 Jan 23.

Swedish University of Agricultural Sciences (SLU), Department of Plant Breeding, Alnarp, Sweden.

Agriculture faces enormous challenges including the need to substantially increase productivity, reduce environmental footprint, and deliver renewable alternatives that are being addressed by developing new oil crops for the future. The efforts include domestication of Lepidium spp. using genomics-aided breeding as a cold hardy perennial high-yielding oil crop that provides substantial environmental benefits, expands the geography for oil crops, and improves farmers' economy. In addition, genetic engineering in Crambe abyssinica may lead to a dedicated industrial oil crop to replace fossil oil. Redirection of photosynthates from starch to oil in plant tubers and cereal endosperm also provides a path for enhancing oil production to meet the growing demands for food, fuel, and biomaterials. Insect pheromone components are produced in seed oil plants in a cost-effective and environmentally friendly pest management replacing synthetically produced pheromones. Autophagy is explored for increasing crop fitness and oil accumulation using genetic engineering in Arabidopsis.
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http://dx.doi.org/10.1016/j.pbi.2019.12.003DOI Listing
August 2020

Identification of Climate and Genetic Factors That Control Fat Content and Fatty Acid Composition of L. Beans.

Front Plant Sci 2019 14;10:1159. Epub 2019 Oct 14.

Mars Chocolate, Miami, FL, United States.

The main ingredients of chocolate are usually cocoa powder, cocoa butter, and sugar. Both the powder and the butter are extracted from the beans of the cacao tree ( L.). The cocoa butter represents the fat in the beans and possesses a unique fatty acid profile that results in chocolate's characteristic texture and mouthfeel. Here, we used a linkage mapping population and phenotypic data of 3,292 samples from 420 progeny which led to the identification of 27 quantitative trait loci (QTLs) for fatty acid composition and six QTLs for fat content. Progeny showed extensive variation in fat levels and composition, with the level of palmitic acid negatively correlated to the sum of stearic acid, oleic acid, and linoleic acid. A major QTL explaining 24% of the relative level of palmitic acid was mapped to the distal end of chromosome 4, and those higher levels of palmitic acid were associated with the presence of a haplotype from the "TSH 1188" parent in the progeny. Within this region of chromosome 4 is the gene, an orthologue and isoform of the stearoyl-acyl carrier protein (ACP) desaturase (SAD) gene in plants, which is involved in fatty acid biosynthesis. Besides allelic differences, we also show that climate factors can change the fatty acid composition in the beans, including a significant positive correlation between higher temperatures and the higher level of palmitic acid. Moreover, we found a significant pollen donor effect from the variety "SIAL 70" which was associated with decreased palmitic acid levels.
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http://dx.doi.org/10.3389/fpls.2019.01159DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6802002PMC
October 2019

Metabolic engineering of soybean seeds for enhanced vitamin E tocochromanol content and effects on oil antioxidant properties in polyunsaturated fatty acid-rich germplasm.

Metab Eng 2020 01 23;57:63-73. Epub 2019 Oct 23.

Center for Plant Science Innovation, University of Nebraska-Lincoln, Lincoln, NE, 68588, USA; Department of Biochemistry, University of Nebraska-Lincoln, Lincoln, NE, 68588, USA. Electronic address:

Soybean seeds produce oil enriched in oxidatively unstable polyunsaturated fatty acids (PUFAs) and are also a potential biotechnological platform for synthesis of oils with nutritional omega-3 PUFAs. In this study, we engineered soybeans for seed-specific expression of a barley homogentisate geranylgeranyl transferase (HGGT) transgene alone and with a soybean γ-tocopherol methyltransferase (γ-TMT) transgene. Seeds for HGGT-expressing lines had 8- to 10-fold increases in total vitamin E tocochromanols, principally as tocotrienols, with little effect on seed oil or protein concentrations. Tocochromanols were primarily in δ- and γ-forms, which were shifted largely to α- and β-tocochromanols with γ-TMT co-expression. We tested whether oxidative stability of conventional or PUFA-enhanced soybean oil could be improved by metabolic engineering for increased vitamin E antioxidants. Selected lines were crossed with a stearidonic acid (SDA, 18:4)-producing line, resulting in progeny with oil enriched in SDA and α- or γ-linoleic acid (ALA, 18:3 or GLA, 18:3), from transgene segregation. Oil extracted from HGGT-expressing lines had ≥6-fold increase in free radical scavenging activity compared to controls. However, the oxidative stability index of oil from vitamin E-enhanced lines was ~15% lower than that of oil from non-engineered seeds and nearly the same or modestly increased in oil from the GLA, ALA and SDA backgrounds relative to controls. These findings show that soybean is an effective platform for producing high levels of free-radical scavenging vitamin E antioxidants, but this trait may have negative effects on oxidative stability of conventional oil or only modest improvement of the oxidative stability of PUFA-enhanced oil.
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http://dx.doi.org/10.1016/j.ymben.2019.10.005DOI Listing
January 2020

Gene Radiation and Positive Selection Contributed to Polyacetylene Metabolism Evolution in Campanulids.

Plant Physiol 2019 10 16;181(2):714-728. Epub 2019 Aug 16.

State Key Laboratory of Biocatalysis and Enzyme Engineering, School of Life Sciences, Hubei University, Wuhan 434200, China

Polyacetylenes (PAs) are bioactive, specialized plant defense compounds produced by some species in the eudicot clade campanulids. Early steps of PA biosynthesis are catalyzed by Fatty Acid Desaturase 2 (). Canonical catalyze desaturation, but divergent forms can catalyze hydroxylation, conjugation, acetylenation, and epoxygenation. These alternate reactions give rise to valuable unusual fatty acids, including the precursors to PAs. The extreme functional diversity of enzymes and the origin of PA biosynthesis are poorly understood from an evolutionary perspective. We focus here on the evolution of the gene family. We uncovered a core eudicot-wide gene duplication event giving rise to two lineages: FAD2-α and FAD2-β. Independent neofunctionalizations in both lineages have resulted in functionally diverse involved in unusual fatty acid biosynthesis. We found significantly accelerated rates of molecular evolution in and use this metric to provide a list of uncharacterized candidates for further exploration of functional diversity. FAD2-α has expanded extensively in Asterales and Apiales, two main clades of campanulids, by ancient gene duplications. Here, we detected positive selection in both Asterales and Apiales lineages, which may have enabled the evolution of PA metabolism in campanulids. Together, these findings also imply that yet uncharacterized FAD2-α copies are involved in later steps of PA biosynthesis. This work establishes a robust phylogenetic framework in which to interpret functional data and to direct future research into the origin and evolution of PA metabolism.
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http://dx.doi.org/10.1104/pp.19.00800DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6776854PMC
October 2019

Nature-Guided Synthesis of Advanced Bio-Lubricants.

Sci Rep 2019 08 12;9(1):11711. Epub 2019 Aug 12.

Department of Materials Science and Engineering, University of North Texas, Denton, TX, USA.

Design of environmentally friendly lubricants derived from renewable resources is highly desirable for many practical applications. Here, Orychophragmus violaceus (Ov) seed oil is found to have superior lubrication properties, and this is based on the unusual structural features of the major lipid species-triacylglycerol (TAG) estolides. Ov TAG estolides contain two non-hydroxylated, glycerol-bound fatty acids (FAs) and one dihydroxylated FA with an estolide branch. Estolide branch chains vary in composition and length, leading to their thermal stability and functional properties. Using this concept, nature-guided estolides of castor oil were synthesized. As predicted, they showed improved lubrication properties similar to Ov seed oil. Our results demonstrate a structure-based design of novel lubricants inspired by natural materials.
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http://dx.doi.org/10.1038/s41598-019-48165-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6690888PMC
August 2019

Expression of the Arabidopsis WRINKLED 1 transcription factor leads to higher accumulation of palmitate in soybean seed.

Plant Biotechnol J 2019 07 18;17(7):1369-1379. Epub 2019 Jan 18.

Center for Plant Science Innovation, University of Nebraska-Lincoln, Lincoln, NE, USA.

Soybean (Glycine max [L.] Merr.) is a commodity crop highly valued for its protein and oil content. The high percentage of polyunsaturated fatty acids in soybean oil results in low oxidative stability, which is a key parameter for usage in baking, high temperature frying applications, and affects shelf life of packaged products containing soybean oil. Introduction of a seed-specific expression cassette carrying the Arabidopsis transcription factor WRINKLED1 (AtWRI1) into soybean, led to seed oil with levels of palmitate up to approximately 20%. Stacking of the AtWRI1 transgenic allele with a transgenic locus harbouring the mangosteen steroyl-ACP thioesterase (GmFatA) resulted in oil with total saturates up to 30%. The creation of a triple stack in soybean, wherein the AtWRI1 and GmFatA alleles were combined with a FAD2-1 silencing allele led to the synthesis of an oil with 28% saturates and approximately 60% oleate. Constructs were then assembled that carry a dual FAD2-1 silencing element/GmFatA expression cassette, alone or combined with an AtWRI1 cassette. These plasmids are designated pPTN1289 and pPTN1301, respectively. Transgenic events carrying the T-DNA of pPTN1289 displayed an oil with stearate levels between 18% and 25%, and oleate in the upper 60%, with reduced palmitate (<5%). While soybean events harboring transgenic alleles of pPTN1301 had similar levels of stearic and oleate levels as that of the pPTRN1289 events, but with levels of palmitate closer to wild type. The modified fatty acid composition results in an oil with higher oxidative stability, and functionality attributes for end use in baking applications.
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http://dx.doi.org/10.1111/pbi.13061DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6577354PMC
July 2019

A Plant Immune Receptor Degraded by Selective Autophagy.

Mol Plant 2019 01 30;12(1):113-123. Epub 2018 Nov 30.

Department of Plant Pathology, University of Nebraska, Lincoln, NE 68588-0722, USA; Center for Plant Science Innovation, University of Nebraska, Lincoln, NE 68588-0660, USA. Electronic address:

Plants recycle non-activated immune receptors to maintain a functional immune system. The Arabidopsis immune receptor kinase FLAGELLIN-SENSING 2 (FLS2) recognizes bacterial flagellin. However, the molecular mechanisms by which non-activated FLS2 and other non-activated plant PRRs are recycled remain not well understood. Here, we provide evidence showing that Arabidopsis orosomucoid (ORM) proteins, which have been known to be negative regulators of sphingolipid biosynthesis, act as selective autophagy receptors to mediate the degradation of FLS2. Arabidopsis plants overexpressing ORM1 or ORM2 have undetectable or greatly diminished FLS2 accumulation, nearly lack FLS2 signaling, and are more susceptible to the bacterial pathogen Pseudomonas syringae. On the other hand, ORM1/2 RNAi plants and orm1 or orm2 mutants generated by the CRISPR/Cas9-mediated gene editing have increased FLS2 accumulation and enhanced FLS2 signaling, and are more resistant to P. syringae. ORM proteins interact with FLS2 and the autophagy-related protein ATG8. Interestingly, overexpression of ORM1 or ORM2 in autophagy-defective mutants showed FLS2 abundance that is comparable to that in wild-type plants. Moreover, FLS2 levels were not decreased in Arabidopsis plants overexpressing ORM1/2 derivatives that do not interact with ATG8. Taken together, these results suggest that selective autophagy functions in maintaining the homeostasis of a plant immune receptor and that beyond sphingolipid metabolic regulation ORM proteins can also act as selective autophagy receptors.
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http://dx.doi.org/10.1016/j.molp.2018.11.011DOI Listing
January 2019

Identification of Genes Encoding Enzymes Catalyzing the Early Steps of Carrot Polyacetylene Biosynthesis.

Plant Physiol 2018 12 17;178(4):1507-1521. Epub 2018 Oct 17.

Center for Plant Science Innovation and Department of Biochemistry, University of Nebraska-Lincoln, Lincoln, Nebraska, 68588

Polyacetylenic lipids accumulate in various Apiaceae species after pathogen attack, suggesting that these compounds are naturally occurring pesticides and potentially valuable resources for crop improvement. These compounds also promote human health and slow tumor growth. Even though polyacetylenic lipids were discovered decades ago, the biosynthetic pathway underlying their production is largely unknown. To begin filling this gap and ultimately enable polyacetylene engineering, we studied polyacetylenes and their biosynthesis in the major Apiaceae crop carrot ( subsp. ). Using gas chromatography and mass spectrometry, we identified three known polyacetylenes and assigned provisional structures to two novel polyacetylenes. We also quantified these compounds in carrot leaf, petiole, root xylem, root phloem, and root periderm extracts. Falcarindiol and falcarinol predominated and accumulated primarily in the root periderm. Since the multiple double and triple carbon-carbon bonds that distinguish polyacetylenes from ubiquitous fatty acids are often introduced by Δ12 oleic acid desaturase (FAD2)-type enzymes, we mined the carrot genome for genes. We identified a family with an unprecedented 24 members and analyzed public, tissue-specific carrot RNA-Seq data to identify coexpressed members with root periderm-enhanced expression. Six candidate genes were heterologously expressed individually and in combination in yeast and Arabidopsis (), resulting in the identification of one canonical FAD2 that converts oleic to linoleic acid, three divergent FAD2-like acetylenases that convert linoleic into crepenynic acid, and two bifunctional FAD2s with Δ12 and Δ14 desaturase activity that convert crepenynic into the further desaturated dehydrocrepenynic acid, a polyacetylene pathway intermediate. These genes can now be used as a basis for discovering other steps of falcarin-type polyacetylene biosynthesis, to modulate polyacetylene levels in plants, and to test the in planta function of these molecules.
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http://dx.doi.org/10.1104/pp.18.01195DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6288749PMC
December 2018

Molecular tools enabling pennycress (Thlaspi arvense) as a model plant and oilseed cash cover crop.

Plant Biotechnol J 2019 04 25;17(4):776-788. Epub 2018 Oct 25.

School of Biological Sciences, Illinois State University, Normal, IL, USA.

Thlapsi arvense L. (pennycress) is being developed as a profitable oilseed cover crop for the winter fallow period throughout the temperate regions of the world, controlling soil erosion and nutrients run-off on otherwise barren farmland. We demonstrate that pennycress can serve as a user-friendly model system akin to Arabidopsis that is well-suited for both laboratory and field experimentation. We sequenced the diploid genome of the spring-type Spring 32-10 inbred line (1C DNA content of 539 Mb; 2n = 14), identifying variation that may explain phenotypic differences with winter-type pennycress, as well as predominantly a one-to-one correspondence with Arabidopsis genes, which makes translational research straightforward. We developed an Agrobacterium-mediated floral dip transformation method (0.5% transformation efficiency) and introduced CRISPR-Cas9 constructs to produce indel mutations in the putative FATTY ACID ELONGATION1 (FAE1) gene, thereby abolishing erucic acid production and creating an edible seed oil comparable to that of canola. We also stably transformed pennycress with the Euonymus alatus diacylglycerol acetyltransferase (EaDAcT) gene, producing low-viscosity acetyl-triacylglycerol-containing seed oil suitable as a diesel-engine drop-in fuel. Adoption of pennycress as a model system will accelerate oilseed-crop translational research and facilitate pennycress' rapid domestication to meet the growing sustainable food and fuel demands.
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http://dx.doi.org/10.1111/pbi.13014DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6419581PMC
April 2019

Discontinuous fatty acid elongation yields hydroxylated seed oil with improved function.

Nat Plants 2018 09 27;4(9):711-720. Epub 2018 Aug 27.

National Key Lab of Crop Genetic Improvement and College of Plant Science and Technology, Huazhong Agricultural University, Wuhan, China.

The biosynthesis of 'unusual' fatty acids with structures that deviate from the common C and C fatty acids has evolved numerous times in the plant kingdom. Characterization of unusual fatty acid biosynthesis has enabled increased understanding of enzyme substrate properties, metabolic plasticity and oil functionality. Here, we report the identification of a novel pathway for hydroxy fatty acid biosynthesis based on the serendipitous discovery of two C fatty acids containing hydroxyl groups at the 7 and 18 carbon atoms as major components of the seed oil of Orychophragmus violaceus, a China-native Brassicaceae. Biochemical and genetic evidence are presented for premature or 'discontinuous' elongation of a 3-OH intermediate by a divergent 3-ketoacyl-CoA (coenzyme A) synthase during a chain extension cycle as the origin of the 7-OH group of the dihydroxy fatty acids. Tribology studies revealed superior high-temperature lubricant properties for O. violaceus seed oil compared to castor oil, a high-performance vegetable oil lubricant. These findings provide a direct pathway for designing a new class of environmentally friendly lubricants and unveil the potential of O. violaceus as a new industrial oilseed crop.
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http://dx.doi.org/10.1038/s41477-018-0225-7DOI Listing
September 2018

Transcriptional Regulation of Vitamin E Biosynthesis during Germination of Dwarf Fan Palm Seeds.

Plant Cell Physiol 2018 Dec;59(12):2490-2501

Department of Evolutionary Biology, Ecology and Environmental Sciences, Faculty of Biology, University of Barcelona, Barcelona, Spain.

Vitamin E, a potent antioxidant either presents in the form of tocopherols and/or tocotrienols depending on the plant species, tissue and developmental stage, plays a major role in protecting lipids from oxidation in seeds. Unlike tocopherols, which have a more universal distribution, the occurrence of tocotrienols is limited primarily to monocot seeds. Dwarf fan palm (Chamaerops humilis var. humilis) seeds accumulate tocotrienols in quiescent and dormant seeds, while tocopherols are de novo synthesized during germination. Here, we aimed to elucidate whether tocopherol biosynthesis is regulated at the transcriptional level during germination in this species. We identified and quantified the expression levels of five genes involved in vitamin E biosynthesis, including TYROSINE AMINOTRANSFERASE (ChTAT), HOMOGENTISATE PHYTYLTRANSFERASE (ChHPT), HOMOGENTISATE GERANYLGERANYL TRANSFERASE (ChHGGT), TOCOPHEROL CYCLASE (ChTC) and TOCOPHEROL γ-METHYLTRANSFERASE (Chγ-TMT). Furthermore, we evaluated to what extent variations in the endogenous contents of hormones and hydrogen peroxide (H2O2) correlated with transcriptional regulation. Results showed an increase of ChTAT and ChHPT levels during seed germination, which correlated with an increase of jasmonic acid (JA), gibberellin4 (GA4), and H2O2 contents, while ChHGGT and Chγ-TMT expression levels decreased, thus clearly indicating vitamin E biosynthesis is diverted to tocopherols rather than to tocotrienols. Exogenous application of jasmonic acid increased tocopherol, but not tocotrienol content, thus confirming its regulatory role in vitamin E biosynthesis during seed germination. It is concluded that the biosynthesis of vitamin E is regulated at the transcriptional level during germination in dwarf fan palm seeds, with ChHPT playing a key role in the diversion of the vitamin E pathway towards tocopherols instead of tocotrienols.
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http://dx.doi.org/10.1093/pcp/pcy170DOI Listing
December 2018

Towards the synthetic design of camelina oil enriched in tailored acetyl-triacylglycerols with medium-chain fatty acids.

J Exp Bot 2018 08;69(18):4395-4402

Department of Biochemistry and Molecular Biophysics, Kansas State University, Manhattan, KS, USA.

The ability to manipulate expression of key biosynthetic enzymes has allowed the development of genetically modified plants that synthesise unusual lipids that are useful for biofuel and industrial applications. By taking advantage of the unique activities of enzymes from different species, tailored lipids with a targeted structure can be conceived. In this study we demonstrate the successful implementation of such an approach by metabolically engineering the oilseed crop Camelina sativa to produce 3-acetyl-1,2-diacyl-sn-glycerols (acetyl-TAGs) with medium-chain fatty acids (MCFAs). Different transgenic camelina lines that had been genetically modified to produce MCFAs through the expression of MCFA-specific thioesterases and acyltransferases were retransformed with the Euonymus alatus gene for diacylglycerol acetyltransferase (EaDAcT) that synthesises acetyl-TAGs. Concomitant RNAi suppression of acyl-CoA:diacylglycerol acyltransferase increased the levels of acetyl-TAG, with up to 77 mole percent in the best lines. However, the total oil content was reduced. Analysis of the composition of the acetyl-TAG molecular species using electrospray ionisation mass spectrometry demonstrated the successful synthesis of acetyl-TAG containing MCFAs. Field growth of high-yielding plants generated enough oil for quantification of viscosity. As part of an ongoing design-test-learn cycle, these results, which include not only the synthesis of 'designer' lipids but also their functional analysis, will lead to the future production of such molecules tailored for specific applications.
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http://dx.doi.org/10.1093/jxb/ery225DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6093318PMC
August 2018

GLUCOSAMINE INOSITOLPHOSPHORYLCERAMIDE TRANSFERASE1 (GINT1) Is a GlcNAc-Containing Glycosylinositol Phosphorylceramide Glycosyltransferase.

Plant Physiol 2018 07 14;177(3):938-952. Epub 2018 May 14.

Joint BioEnergy Institute, Emeryville, California 94608

Glycosylinositol phosphorylceramides (GIPCs), which have a ceramide core linked to a glycan headgroup of varying structures, are the major sphingolipids in the plant plasma membrane. Recently, we identified the major biosynthetic genes for GIPC glycosylation in Arabidopsis () and demonstrated that the glycan headgroup is essential for plant viability. However, the function of GIPCs and the significance of their structural variation are poorly understood. Here, we characterized the Arabidopsis glycosyltransferase GLUCOSAMINE INOSITOLPHOSPHORYLCERAMIDE TRANSFERASE1 (GINT1) and showed that it is responsible for the glycosylation of a subgroup of GIPCs found in seeds and pollen that contain GlcNAc and GlcN [collectively GlcN(Ac)]. In Arabidopsis plants, loss of the GlcN(Ac) GIPCs did not affect vegetative growth, although seed germination was less sensitive to abiotic stress than in wild-type plants. However, in rice, where GlcN(Ac) containing GIPCs are the major GIPC subgroup in vegetative tissue, loss of GINT1 was seedling lethal. Furthermore, we could produce, de novo, "rice-like" GlcN(Ac) GIPCs in Arabidopsis leaves, which allowed us to test the function of different sugars in the GIPC headgroup. This study describes a monocot GIPC biosynthetic enzyme and shows that its Arabidopsis homolog has the same biochemical function. We also identify a possible role for GIPCs in maintaining cell-cell adhesion.
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http://dx.doi.org/10.1104/pp.18.00396DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6053017PMC
July 2018
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