Mutation of the TGD1 chloroplast envelope protein affects phosphatidate metabolism in Arabidopsis. Plant Cell

Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan 48824, USA.
The Plant Cell (Impact Factor: 9.34). 12/2005; 17(11):3094-110. DOI: 10.1105/tpc.105.035592
Source: PubMed


Phosphatidate (PA) is a central metabolite of lipid metabolism and a signaling molecule in many eukaryotes, including plants. Mutations in a permease-like protein, TRIGALACTOSYLDIACYLGLYCEROL1 (TGD1), in Arabidopsis thaliana caused the accumulation of triacylglycerols, oligogalactolipids, and PA. Chloroplast lipids were altered in their fatty acid composition consistent with an impairment of lipid trafficking from the endoplasmic reticulum (ER) to the chloroplast and a disruption of thylakoid lipid biosynthesis from ER-derived precursors. The process mediated by TGD1 appears to be essential as mutation of the protein caused a high incidence of embryo abortion. Isolated tgd1 mutant chloroplasts showed a decreased ability to incorporate PA into galactolipids. The TGD1 protein was localized to the inner chloroplast envelope and appears to be a component of a lipid transporter. As even partial disruption of TGD1 function has drastic consequences on central lipid metabolism, the tgd1 mutant provides a tool to explore regulatory mechanisms governing lipid homeostasis and lipid trafficking in plants.

Download full-text


Available from: John Froehlich, May 27, 2014
1 Follower
34 Reads
  • Source
    • "One of the diagnostic phenotypes for all tgd mutants is the accumulation of oligogalactolipids including TGDG due to the activation of a galactolipid : galactolipid galactosyltransferase ( GGGT ) ( Xu et al . , 2003 , 2005 ) . This enzyme is localized to the outer chloroplast envelope membrane ( Xu et al . , 2003 ) and catalyzes the processive transfer of the galactosyl residue of MGDG to various galactolipids , giving rise to oligogalactolipids and DAG . A recent study showed that GGGT is identical to SENSITIVE TO FREEZING2 ( SFR2 ) ( Moellering et al . "
    [Show abstract] [Hide abstract]
    ABSTRACT: The biogenesis of photosynthetic membranes in the plastids of higher plants requires an extensive supply of lipid precursors from the endoplasmic reticulum (ER). Four TRIGALACTOSYLDIACYLGLYCEROL (TGD) proteins (TGD1,2,3,4) have thus far been implicated in this lipid transfer process. While TGD1, TGD2, and TGD3 constitute an ATP binding cassette transporter complex residing in the plastid inner envelope, TGD4 is a transmembrane lipid transfer protein present in the outer envelope. These observations raise questions regarding how lipids transit across the aqueous intermembrane space. Here, we describe the isolation and characterization of a novel Arabidopsis thaliana gene, TGD5. Disruption of TGD5 results in similar phenotypic effects as previously described in tgd1,2,3,4 mutants, including deficiency of ER-derived thylakoid lipids, accumulation of oligogalactolipids, and triacylglycerol. Genetic analysis indicates that TGD4 is epistatic to TGD5 in ER-to-plastid lipid trafficking, whereas double mutants of a null tgd5 allele with tgd1-1 or tgd2-1 show a synergistic embryo-lethal phenotype. TGD5 encodes a small glycine-rich protein that is localized in the envelope membranes of chloroplasts. Coimmunoprecipitation assays show that TGD5 physically interacts with TGD1, TGD2, TGD3, and TGD4. Collectively, these results suggest that TGD5 facilitates lipid transfer from the outer to the inner plastid envelope by bridging TGD4 with the TGD1,2,3 transporter complex.
    The Plant Cell 09/2015; DOI:10.1105/tpc.15.00394 · 9.34 Impact Factor
  • Source
    • "In vivo pulse chase studies indicate that PC (detected in envelope/chloroplast ) synthesized in the ER could be the immediate precursor for galactolipid synthesis in chloroplasts [15] [16] [17] [30] [31]. In addition, diacylglycerol (DAG) [36], phosphatic acid (PA) [41] and lyso-PC [23] have been suggested to be galactolipid precursors transported from the ER. Since chloroplasts lack capacity to synthesize the head group of PC, and both the outer envelope and the ER contain a significant amount of PC it seems likely that PC is transported from the ER whether or not it is the major precursor for galactolipids. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Chloroplasts maintain their lipid balance through a tight interplay with the endoplasmic reticulum (ER). The outer envelope membrane of chloroplasts contains a large proportion of the phospholipid phospatidylcholine (PC), which is synthesized in the ER and also a possible precursor for thylakoid galactolipids. The mechanism for PC transport from the ER to chloroplasts is not known. Using isolated chloroplasts and liposomes containing radiolabelled PC we investigated non-vesicular transport of PC in vitro. PC uptake in chloroplasts was time- and temperature-dependent, but nucleotide-independent. Increased radius of liposomes stimulated PC uptake, and protease treatment of the chloroplasts impaired PC uptake. This implies that the chloroplast outer envelopes contains an exposed proteinaceous machinery for the uptake of PC from closely apposed membranes. Copyright © 2014. Published by Elsevier B.V.
    FEBS Letters 12/2014; 589(1). DOI:10.1016/j.febslet.2014.11.044 · 3.17 Impact Factor
  • Source
    • "palm, olive and avocado) are by far the largest source of plant produced oils, many other tissues are capable of synthesising triacylglycerols and a number of studies reported the presence of cytosolic lipid droplets in the leaf mesophyll cells of many plant species (Lersten et al., 2006; Lin and Oliver 2008). TAGs notably accumulate during senescence in leaves (Kaup et al., 2002), under stress (Sakaki et al., 1990) and in Arabidopsis mutants disrupted in ER to chloroplast lipid trafficking (Xu et al., 2005). Nevertheless, the oil content of vegetative tissues is typically very low in the majority of plant species, particularly in photosynthetic tissues, representing less than 0.2% of dry weight in leaves (Kelly et al., 2013; Vanhercke et al., 2013). "
    [Show abstract] [Hide abstract]
    ABSTRACT: The world faces considerable challenges including how to produce more biomass for food , feed , fuel and industrial feedstock without significantly impacting on our environment or increasing our consumption of limited resources such as water or petroleum-derived carbon. This has been described as sustainable intensification. Oleaginous crops have the potential to provide renewable resources for all these commodities , provided they can be engineered to meet end-use requirements , and that they can be produced on sufficient scale to meet current growing world population and industrial demand. Although traditional breeding methods have been used successfully to modify the fatty acid composition of oils , metabolic engineering provides a more rapid and direct method for manipulating plant lipid composition . Recent advances in our understanding of the biochemical mechanisms of seed oil biogenesis and the cloning of genes involved in fatty acid and oil metabolic pathways , have allowed the generation of oilseed crops that produce ' designer oils ' tailored for specific applications and the conversion of high biomass crops into novel oleaginous crops. However , improvement of complex quantitative traits in oilseed crops remains more challenging as the underlying genetic determinants are still poorly understood. Technological advances in sequencing and computing have allowed the development of an association genetics method applicable to crops with complex genomes. Associative transcriptomics approaches and high throughput lipidomic profiling can be used to identify the genetic components controlling quantitative variation for lipid related traits in polyploid crops like oilseed rape and provide molecular tools for marker assisted breeding. In this review we are citing examples of traits with potential for bio-refining that can be harvested as co-products in seeds , but also in non-harvested biomass. Les oléagineux en tant que plateformes intégrées de production pour l ' alimentation humaine et animale , les carburants et les matières premières industrielles renouvelables : Manipulation de la composition lipidique de la plante par ingénierie métabolique et nouvelles opportunités d ' associations génétiques pour l ' amé-lioration des cultures et la valorisation des coproduits. Le monde fait face à des défis considérables , incluant le moyen de produire davantage de biomasse pour l ' alimentation humaine et animale , les carburants et les matières pre-mières industrielles , et ce sans impact environnemental significatif ou sans accroître notre consommation de ressources limitées comme l ' eau ou le carbone dérivé du pétrole. Cela a été décrit comme de l ' intensification durable. Les oléa-gineux disposent du potentiel nécessaire pour fournir des ressources renouvelables pour toutes ces matières premières , sous réserve qu ' ils puissent être manipulés de manière à respecter les exigences d ' utilisation finale et qu ' ils puissent être produits à une échelle suffisante , répondant ainsi à une pression démographique mondiale et à une demande indus-trielle croissantes. Bien que des méthodes de reproduction traditionnelles aient été utilisées avec succès pour modifier la composition en acides gras des huiles , l ' ingénierie métabolique fournit une méthode plus rapide et plus directe pour manipuler la composition en lipides des végétaux. Des avancées récentes dans notre compréhension des mécanismes biochimiques de biogenèse d ' huile dans les graines et le clonage de gènes impliqués dans les voies métaboliques des acides gras et huiles , ont permis la génération d ' oléagineux produisant des « huiles sur mesure » , adaptées à des demandes spécifiques et la conversion de variétés à haut potentiel de biomasse en nouvelles variétés oléagineuses. Cependant , l ' amélioration de caractères quantitatifs complexes chez les oléagineux demeure difficile , les déterminants génétiques sous-jacents étant toujours mal compris. Néanmoins , des avancées technologiques dans le séquençage des acides nucléiques et le traitement informatique ont permis le développement d ' une méthode de génétique d ' association applicable aux plantes ayant des génomes complexes. Ainsi , des approches de transcriptomiques associatives et de pro-filage lipidomique à haut débit peuvent être utilisées afin d ' identifier les composants génétiques contrôlant la variation quantitative de caractères liés aux lipides chez les plantes polyploïdes comme le colza , et de fournir des outils molé-culaires pour la sélection assistée par marqueur moléculaire. Dans cette revue , nous citons des exemples de caractères présentant un potentiel pour le bioraffinage qui peuvent être récoltés comme des coproduits dans les graines , mais aussi dans la biomasse non-récoltée. Mots clés : Amélioration des plantes / plantes oléagineuses / ingénierie métabolique / huiles specialisées / Études d ' association pangénomique / Études association trancriptomique / Co-produits
    OCL - Oleagineux Corps Gras Lipides 12/2014; 2014(21 (6)). DOI:10.1051/ocl/2014042
Show more