Dual Role for Phospholipid:Diacylglycerol Acyltransferase: Enhancing Fatty Acid Synthesis and Diverting Fatty Acids from Membrane Lipids to Triacylglycerol in Arabidopsis Leaves

Biosciences Department, Brookhaven National Laboratory, Upton, New York 11973.
The Plant Cell (Impact Factor: 9.34). 09/2013; 25(9). DOI: 10.1105/tpc.113.117358
Source: PubMed


There is growing interest in engineering green biomass to expand the production of plant oils as feed and biofuels. Here, we show that PHOSPHOLIPID:DIACYLGLYCEROL ACYLTRANSFERASE1 (PDAT1) is a critical enzyme involved in triacylglycerol (TAG) synthesis in leaves. Overexpression of PDAT1 increases leaf TAG accumulation, leading to oil droplet overexpansion through fusion. Ectopic expression of oleosin promotes the clustering of small oil droplets. Coexpression of PDAT1 with oleosin boosts leaf TAG content by up to 6.4% of the dry weight without affecting membrane lipid composition and plant growth. PDAT1 overexpression stimulates fatty acid synthesis (FAS) and increases fatty acid flux toward the prokaryotic glycerolipid pathway. In the trigalactosyldiacylglycerol1-1 mutant, which is defective in eukaryotic thylakoid lipid synthesis, the combined overexpression of PDAT1 with oleosin increases leaf TAG content to 8.6% of the dry weight and total leaf lipid by fourfold. In the plastidic glycerol-3-phosphate acyltransferase1 mutant, which is defective in the prokaryotic glycerolipid pathway, PDAT1 overexpression enhances TAG content at the expense of thylakoid membrane lipids, leading to defects in chloroplast division and thylakoid biogenesis. Collectively, these results reveal a dual role for PDAT1 in enhancing fatty acid and TAG synthesis in leaves and suggest that increasing FAS is the key to engineering high levels of TAG accumulation in green biomass.

28 Reads
    • "Recent gains in enhancing oilseed TAG content have involved multiple approaches: for example, the manipulation of transcriptional master regulators such as WRINKLED1 (WRI1) to drive glycolysis and fatty acid (FA) synthesis (Cernac and Benning, 2004; Shen et al., 2010), overexpression of diacylglycerol acyltransferase (DGAT1) to increase sink strength for TAG (Jako et al., 2001), or reducing turnover by inhibition of lipolytic reactions (Fan et al., 2013; Kelly et al., 2013; Vanhercke et al., 2014; Winichayakul et al., 2013). These three approaches have been termed 'push' (increasing FA synthesis), 'pull' (enhancing TAG assembly) and 'protect' (increasing TAG storage or reducing breakdown). "
    [Show abstract] [Hide abstract]
    ABSTRACT: We have identified a novel means to achieve substantially increased vegetative biomass and oilseed production in the model plant Arabidopsis thaliana. Endogenous isoforms of starch branching enzyme (SBE) were substituted by either one of the endosperm-expressed maize (Zea mays L.) branching isozymes, ZmSBEI or ZmSBEIIb. Transformants were compared with the starch-free background and with the wild-type plants. Each of the maize-derived SBEs restored starch biosynthesis but both morphology and structure of starch particles were altered. Altered starch metabolism in the transformants is associated with enhanced biomass formation and more-than-trebled oilseed production while maintaining seed oil quality. Enhanced oilseed production is primarily due to an increased number of siliques per plant whereas oil content and seed number per silique are essentially unchanged or even modestly decreased. Introduction of cereal starch branching isozymes into oilseed plants represents a potentially useful strategy to increase biomass and oilseed production in related crops and manipulate the structure and properties of leaf starch. © 2015 Society for Experimental Biology, Association of Applied Biologists and John Wiley & Sons Ltd.
    Plant Biotechnology Journal 08/2015; DOI:10.1111/pbi.12453 · 5.75 Impact Factor
  • Source
    • "For the production of microalgal oils, the interdependence of total lipid content, fatty acid composition, and biomass productivity throughout cultivation is critical [79], [80]. Novel approaches to maximize carbon storage as neutral lipids can lead to significant benefits for algae biotechnology, biomanufacturing, and bioenergy [81]. The accumulation of different lipids during heterotrophy and autotrophy can be especially important for the interrogation of lipid biosynthetic pathways in commercially relevant Chlorella species. "
    [Show abstract] [Hide abstract]
    ABSTRACT: While photosynthetic microalgae, such as Chlorella, serve as feedstocks for nutritional oils and biofuels, heterotrophic cultivation can augment growth rates, support high cell densities, and increase triacylglycerol (TAG) lipid content. However, these species differ significantly in their photoautotrophic and heterotrophic characteristics. In this study, the phylogeny of thirty Chlorella strains was determined in order to inform bioprospecting efforts and detailed physiological assessment of three species. The growth kinetics and lipid biochemistry of C. protothecoides UTEX 411, C. vulgaris UTEX 265, and C. sorokiniana UTEX 1230 were quantified during photoautotrophy in Bold's basal medium (BBM) and heterotrophy in BBM supplemented with glucose (10 g L-1). Heterotrophic growth rates of UTEX 411, 265, and 1230 were found to be 1.5-, 3.7-, and 5-fold higher than their respective autotrophic rates. With a rapid nine-hour heterotrophic doubling time, Chlorella sorokiniana UTEX 1230 maximally accumulated 39% total lipids by dry weight during heterotrophy compared to 18% autotrophically. Furthermore, the discrete fatty acid composition of each strain was examined in order to elucidate lipid accumulation patterns under the two trophic conditions. In both modes of growth, UTEX 411 and 265 produced 18∶1 as the principal fatty acid while UTEX 1230 exhibited a 2.5-fold enrichment in 18∶2 relative to 18∶1. Although the total lipid content was highest in UTEX 411 during heterotrophy, UTEX 1230 demonstrated a two-fold increase in its heterotrophic TAG fraction at a rate of 28.9 mg L-1 d-1 to reach 22% of the biomass, corresponding to as much as 90% of its total lipids. Interestingly, UTEX 1230 growth was restricted during mixotrophy and its TAG production rate was suppressed to 18.2 mg L-1 d-1. This constraint on carbon flow raises intriguing questions about the impact of sugar and light on the metabolic regulation of microalgal lipid biosynthesis.
    PLoS ONE 04/2014; 9(4):e92460. DOI:10.1371/journal.pone.0092460 · 3.23 Impact Factor
  • Source
    • "For example, expression of the WRINKLED1 (WRI1) transcription factor can be used to drive glycolysis and fatty acid synthesis (Cernac and Benning, 2004), expression of DIACYLGLYCEROLACYL TRANSFERASE1 (DGAT1) can be used to draw fatty acids into TAG (Jako et al., 2001), and turnover can also be minimized by disrupting lipolysis (Fan et al., 2013; Kelly et al., 2013b; Vanhercke et al., 2013; Winichayakul et al., 2013). Here, we investigate the effects of stacking these gene modifications on seed oil content and yield in Arabidopsis. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Increasing the yield of oilseed crops is an important objective for biotechnologists. A number of individual genes involved in triacylglycerol metabolism have previously been reported to enhance the oil content of seeds when their expression is altered. However, it has yet to be established whether specific combinations of these genes can be used to achieve an additive effect and whether this leads to enhanced yield. Using Arabidopsis thaliana as an experimental system we show that seed-specific over-expression of WRINKLED1 (a transcriptional regulator of glycolysis and fatty acid synthesis) and DIACYLGLYCEROL ACYLTRANSFERASE1 (a triacylglycerol biosynthetic enzyme) combined with suppression of the triacylglycerol lipase SUGAR-DEPENDENT1 results in a higher percentage seed oil content and greater seed mass than manipulation of each gene individually. Analysis of total seed yield per plant suggests that, despite a reduction in seed number, the total yield of oil is also increased.
    Plant physiology 04/2014; 165(1). DOI:10.1104/pp.114.236430 · 6.84 Impact Factor
Show more