Biochemical pathways in seed oil synthesis
TL;DR: Oil produced in plant seeds is utilized as a major source of calories for human nutrition, as feedstocks for non-food uses such as soaps and polymers, and can serve as a high-energy biofuel.
About: This article is published in Current Opinion in Plant Biology.The article was published on 2013-06-01 and is currently open access. It has received 386 citations till now.
Citations
More filters
TL;DR: A set of heterologous genes capable of efficiently directing synthesis of omega-3 long-chain polyunsaturated fatty acids in the seed oil of the crop Camelina sativa are described, while simultaneously avoiding accumulation of undesirable intermediate fatty acids.
Abstract: Omega-3 (also called n-3) long-chain polyunsaturated fatty acids (≥C20; LC-PUFAs) are of considerable interest, based on clear evidence of dietary health benefits and the concurrent decline of global sources (fish oils). Generating alternative transgenic plant sources of omega-3 LC-PUFAs, i.e. eicosapentaenoic acid (20:5 n-3, EPA) and docosahexaenoic acid (22:6 n-3, DHA) has previously proved problematic. Here we describe a set of heterologous genes capable of efficiently directing synthesis of these fatty acids in the seed oil of the crop Camelina sativa, while simultaneously avoiding accumulation of undesirable intermediate fatty acids. We describe two iterations: RRes_EPA in which seeds contain EPA levels of up to 31% (mean 24%), and RRes_DHA, in which seeds accumulate up to 12% EPA and 14% DHA (mean 11% EPA and 8% DHA). These omega-3 LC-PUFA levels are equivalent to those in fish oils, and represent a sustainable, terrestrial source of these fatty acids. We also describe the distribution of these non-native fatty acids within C. sativa seed lipids, and consider these data in the context of our current understanding of acyl exchange during seed oil synthesis.
282 citations
Cites background from "Biochemical pathways in seed oil sy..."
...Different plants probably utilize a combination of routes to incorporate novel fatty acids into TAG (Bates et al., 2013)....
[...]
...© 2013 The Authors The Plant Journal © 2013 John Wiley & Sons Ltd., The Plant Journal, (2014), 77, 198–208 Different plants probably utilize a combination of routes to incorporate novel fatty acids into TAG (Bates et al., 2013)....
[...]
TL;DR: These strategies which include modulating light intensity in cultures, controlling and varying CO2 levels and temperature, inducing nutrient starvation in the culture, the implementation of stress by incorporating heavy metal or inducing a high salinity condition, and the use of metabolic and genetic engineering techniques coupled with nanotechnology are reviewed.
Abstract: The use of fossil fuels has been strongly related to critical problems currently affecting society, such as: global warming, global greenhouse effects and pollution. These problems have affected the homeostasis of living organisms worldwide at an alarming rate. Due to this, it is imperative to look for alternatives to the use of fossil fuels and one of the relevant substitutes are biofuels. There are different types of biofuels (categories and generations) that have been previously explored, but recently, the use of microalgae has been strongly considered for the production of biofuels since they present a series of advantages over other biofuel production sources: (a) they don’t need arable land to grow and therefore do not compete with food crops (like biofuels produced from corn, sugar cane and other plants) and; (b) they exhibit rapid biomass production containing high oil contents, at least 15 to 20 times higher than land based oleaginous crops. Hence, these unicellular photosynthetic microorganisms have received great attention from researches to use them in the large-scale production of biofuels. However, one disadvantage of using microalgae is the high economic cost due to the low-yields of lipid content in the microalgae biomass. Thus, development of different methods to enhance microalgae biomass, as well as lipid content in the microalgae cells, would lead to the development of a sustainable low-cost process to produce biofuels. Within the last 10 years, many studies have reported different methods and strategies to induce lipid production to obtain higher lipid accumulation in the biomass of microalgae cells; however, there is not a comprehensive review in the literature that highlights, compares and discusses these strategies. Here, we review these strategies which include modulating light intensity in cultures, controlling and varying CO2 levels and temperature, inducing nutrient starvation in the culture, the implementation of stress by incorporating heavy metal or inducing a high salinity condition, and the use of metabolic and genetic engineering techniques coupled with nanotechnology.
226 citations
TL;DR: Advances in the understanding of enzymes and regulatory proteins of acyl lipid biosynthesis and turnover are described with a focus on carbon and energetic aspects and how changes in environmental factors can impact lipid metabolism are summarized.
221 citations
Cites background from "Biochemical pathways in seed oil sy..."
...Nevertheless, for now it can be assumed that the pathways identified in higher plants [239-241] are on the whole followed in eukaryotic algae though, perhaps, in a simpler form with less genetic redundancy [31](Figure 4)....
[...]
TL;DR: Algal strains of industrial potential have been described for the production of high-value products, such as carotenoids and PUFAs, or for biofuels production, and novel promising strains continue to be reported, however, phototrophic production of algal products is considered 2–5 times more expensive than competing pathways for both high- Value products and bulk biomass.
Abstract: Microalgae are considered a promising source for various high-value products, including carotenoids and omega-3 and omega-6 polyunsaturated fatty acids (PUFAs). Excluding production by heterotrophic fermentation, only two microalgal high-value products are successfully marketed at a relevant scale: β-carotene from Dunaliella salina, and astaxanthin from Haematococcus pluvialis. In addition, Chlorella and Spirulina biomass are marketed in large volumes as nutraceuticals, and phycocyanin extracted from cyanobacteria has gained major market share recently. Additional algal strains of industrial potential have been described for the production of high-value products, such as carotenoids and PUFAs, or for biofuels production, and novel promising strains continue to be reported. However, phototrophic production of algal products is considered 2–5 times more expensive than competing pathways for both high-value products and bulk biomass. Recent—and often still unpublished—advances have been made in deci...
207 citations
TL;DR: Different transport mechanisms for land plants and green algae - in the model systems Arabidopsis thaliana, Chlamydomonas reinhardtii - are compared, thereby providing a current perspective on protein-mediated FA and lipid trafficking in photosynthetic cells.
186 citations
References
More filters
TL;DR: This chapter focuses on the metabolic pathways that are associated with the biosynthesis and degradation of the acyl lipids that represent their major form of carbon and energy storage in Arabidopsis.
Abstract: Acyl lipids in Arabidopsis and all other plants have a myriad of diverse functions. These include providing the core diffusion barrier of the membranes that separates cells and subcellular organelles. This function alone involves more than 10 membrane lipid classes, including the phospholipids, galactolipids, and sphingolipids, and within each class the variations in acyl chain composition expand the number of structures to several hundred possible molecular species. Acyl lipids in the form of triacylglycerol account for 35% of the weight of Arabidopsis seeds and represent their major form of carbon and energy storage. A layer of cutin and cuticular waxes that restricts the loss of water and provides protection from invasions by pathogens and other stresses covers the entire aerial surface of Arabidopsis. Similar functions are provided by suberin and its associated waxes that are localized in roots, seed coats, and abscission zones and are produced in response to wounding. This chapter focuses on the metabolic pathways that are associated with the biosynthesis and degradation of the acyl lipids mentioned above. These pathways, enzymes, and genes are also presented in detail in an associated website (ARALIP: http://aralip.plantbiology.msu.edu/). Protocols and methods used for analysis of Arabidopsis lipids are provided. Finally, a detailed summary of the composition of Arabidopsis lipids is provided in three figures and 15 tables.
1,169 citations
TL;DR: B budding yeast PDAT and its relatives in fission yeast and Arabidopsis form a distinct branch within this protein superfamily, indicating that a separate PDAT enzyme arose at an early point in evolution.
Abstract: Triacylglycerol (TAG) is known to be synthesized in a reaction that uses acyl-CoA as acyl donor and diacylglycerol (DAG) as acceptor, and which is catalyzed by the enzyme acyl-CoA:diacylglycerol acyltransferase. We have found that some plants and yeast also have an acyl-CoA-independent mechanism for TAG synthesis, which uses phospholipids as acyl donors and DAG as acceptor. This reaction is catalyzed by an enzyme that we call phospholipid:diacylglycerol acyltransferase, or PDAT. PDAT was characterized in microsomal preparations from three different oil seeds: sunflower, castor bean, and Crepis palaestina. We found that the specificity of the enzyme for the acyl group in the phospholipid varies between these species. Thus, C. palaestina PDAT preferentially incorporates vernoloyl groups into TAG, whereas PDAT from castor bean incorporates both ricinoleoyl and vernoloyl groups. We further found that PDAT activity also is present in yeast microsomes. The substrate specificity of this PDAT depends on the head group of the acyl donor, the acyl group transferred, and the acyl chains of the acceptor DAG. The gene encoding the enzyme was identified. The encoded PDAT protein is related to lecithin:cholesterol acyltransferase, which catalyzes the acyl-CoA-independent synthesis of cholesterol esters. However, budding yeast PDAT and its relatives in fission yeast and Arabidopsis form a distinct branch within this protein superfamily, indicating that a separate PDAT enzyme arose at an early point in evolution.
833 citations
"Biochemical pathways in seed oil sy..." refers background in this paper
...Second, direct transfer of a FA from PC to DAG producing TAG by the phospholipid:diacylglycerol acyltransferase (PDAT; Figure 1c, purple arrows) [54]....
[...]
TL;DR: Oil-accumulating seedlings showed aberrant development consistent with a prolonged embryonic state, and the putative AP2/EREBP transcription factor WRINKLED1 (WRI1) is involved in the regulation of seed storage metabolism in Arabidopsis.
Abstract: The accumulation of storage compounds during seed development ensures the survival of the young seedling, and also provides nutrition to humans and animals in the form of foods and feeds. The putative AP2/EREBP transcription factor WRINKLED1 (WRI1) is involved in the regulation of seed storage metabolism in Arabidopsis. A splicing mutant allele, wri1-1, caused the reduction of seed oil accumulation. Glycolysis was compromised in this mutant, rendering developing embryos unable to efficiently convert sucrose into precursors of triacylglycerol biosynthesis. Expression of the WRINKLED1 cDNA under the control of the cauliflower mosaic virus 35S-promoter led to increased seed oil content. Moreover, the ectopic expression of the WRINKLED1 cDNA caused the accumulation of triacylglycerols in developing seedlings. This effect depended upon the presence of glucose in the growth medium or other sugars readily metabolized to glucose. Oil-accumulating seedlings showed aberrant development consistent with a prolonged embryonic state.
571 citations
"Biochemical pathways in seed oil sy..." refers background in this paper
...An increase in maize embyo oil by overexpressing the WRI1 transcription factor [16 ] and increased soybean and B. napus oil by expression of DGAT [78,79], represent successes at Current Opinion in Plant Biology 2013, 16:358–364 source and sink levels, respectively....
[...]
...Shen B, Allen WB, Zheng PZ, Li CJ, Glassman K, Ranch J, Nubel D, Tarczynski MC: Expression of ZmLEC1 and ZmWRI1 Increases Seed Oil Production in Maize....
[...]
...Thus, WRI1 expression is www.sciencedirect.com...
[...]
...The transcription factor WRI1 [14] controls the expression of at least 15 enzymes including pyruvate dehydrogenase, ACCase and members of the FA synthesis and glycolytic pathways [15 ]....
[...]
...As in seeds, WRI1 is a key determinant that controls oil synthesis....
[...]
TL;DR: An enzyme is found in chicken liver that catalyzes the net synthesis of triglyceride according to the following equation:.
524 citations
"Biochemical pathways in seed oil sy..." refers background in this paper
...The pathway was first characterized in animals over 50 years ago [25,26] and soon after in plants [27]....
[...]
TL;DR: It is suggested that DGAT1 and DGAT2 have nonredundant functions in plants and that the production of storage oils, including those containing unusual fatty acids, occurs in distinct ER subdomains.
Abstract: Seeds of the tung tree (Vernicia fordii) produce large quantities of triacylglycerols (TAGs) containing ∼80% eleostearic acid, an unusual conjugated fatty acid. We present a comparative analysis of the genetic, functional, and cellular properties of tung type 1 and type 2 diacylglycerol acyltransferases (DGAT1 and DGAT2), two unrelated enzymes that catalyze the committed step in TAG biosynthesis. We show that both enzymes are encoded by single genes and that DGAT1 is expressed at similar levels in various organs, whereas DGAT2 is strongly induced in developing seeds at the onset of oil biosynthesis. Expression of DGAT1 and DGAT2 in yeast produced different types and proportions of TAGs containing eleostearic acid, with DGAT2 possessing an enhanced propensity for the synthesis of trieleostearin, the main component of tung oil. Both DGAT1 and DGAT2 are located in distinct, dynamic regions of the endoplasmic reticulum (ER), and surprisingly, these regions do not overlap. Furthermore, although both DGAT1 and DGAT2 contain a similar C-terminal pentapeptide ER retrieval motif, this motif alone is not sufficient for their localization to specific regions of the ER. These data suggest that DGAT1 and DGAT2 have nonredundant functions in plants and that the production of storage oils, including those containing unusual fatty acids, occurs in distinct ER subdomains.
523 citations
"Biochemical pathways in seed oil sy..." refers background in this paper
...How such channeling is achieved is unknown but may involve enzymes specific for unusual FAs [63,65,74–76] as well as separation of lipid biosynthetic activities to different subdomains of the ER membrane [44,77]....
[...]
...Current Opinion in Plant Biology 2013, 16:358–364 and Vernicia fordii, DGAT2 is more highly expressed than DGAT1 during seed maturation and DGAT2 appears to be the enzyme responsible for most TAG synthesis [44,45]....
[...]