Lipidomic Analysis of Plastidial Octanoyltransferase Mutants of Arabidopsis thaliana

International audiencePlant de novo fatty acid synthesis takes place in the plastid using acetyl-coenzyme A (acetyl-CoA) as the main precursor. This first intermediate is produced from pyruvate through the action of the plastidial pyruvate dehydrogenase complex (PDH), which catalyses the oxidative decarboxylation of pyruvate to produce acetyl-CoA, CO 2 , and NADH. For the proper functioning of this complex, lipoic acid is required to be bound to the dihydrolipoamide S-acetyltransferase E2 subunit of PDH. Octanoyltransferase (LIP2; EC 2.3.1.181) and lipoyl synthase (LIP1; EC 2.8.1.8) are the enzymes involved in the biosynthesis of this essential cofactor. In Arabidopsis plastids, an essential lipoyl synthase (AtLIP1p) and two redundant octanoyltransferases (AtLIP2p1 and AtLIP2p2) have been described. In the present study, the lipidomic characterization of Arabidopsis octanoyltransferase mutants reveals new insight into the lipoylation functions within plastid metabolism. Lipids and fatty acids from mature seeds and seedlings from Atlip2p1 and Atlip2p2 mutants were analysed by gas chromatography (GC) and liquid chromatography-electrospray ionization high-resolution mass spectrometry (LC-ESI-HRMS2), the analysis revealed changes in fatty acid profiles that showed similar patterns in both mutant seeds and seedlings and in the lipid species containing those fatty acids. Although both mutants showed similar tendencies, the lack of the AtLIP2p2 isoform produced a more acute variation in its lipids profile. These changes in fatty acid composition and the increase in their content per seed point to the interference of octanoyltransferases in the fatty acid synthesis flux in Arabidopsis thaliana seeds

Biomass evolution in porous media and its effects on permeability under starvation conditions

The purpose of this study was to understand bacteria profile modification and its applications in subsurface biological operations such as biobarrier formation, in situ bioremediation, and microbial-enhanced oil recovery. Biomass accumulation and evolution in porous media were investigated both experimentally and theoretically. To study both nutrient-rich and carbon-source-depleted conditions, Leuconostoc mesenteroides was chosen because of its rapid growth rate and exopolymer production rate. Porous micromodels were used to study the effects of biomass evolution on the permeability of a porous medium. Bacterial starvation was initiated by switching the feed from a nutrient solution to a buffer solution in order to examine biofilm stability under nutrient-poor conditions. Four different evolution patterns were identified during the nutrient-rich and nutrient-depleted conditions used in the micromodel experiments. In phase I, the permeability of the porous micromodel decreased as a result of biomass accumulation in pore bodies and pore throats. In phase II, starvation conditions were initiated. The depletion of nutrient in the phase II resulted in slower growth of the biofilm causing the permeability to reach a minimum as all the remaining nutrients were consumed. In phase III, permeability began to increase due to biofilm sloughing caused by shear stress. In phase IV, shear stress remained below the critical shear stress for sloughing and the biofilm remained stable for long periods of time during starvation. The critical shear stress for biofilm sloughing provided an indication of biofilm strength. Shear removal of biofilms occurred when shear stress exceeded critical shear stress. A network model was used to describe the biofilm formation phenomenon and the existence of a critical shear stress. Simulations were in qualitative agreement with the experimental results, and demonstrate the existence of a critical shear stress. © 2000 John Wiley & Sons, Inc. Biotechnol Bioeng 69: 47–56, 2000.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/34337/1/6_ftp.pd

Production d'acides gras branchés, par génie génétique, dans des embryons de lin (études préliminaires sur le colza)

COMPIEGNE-BU (601592101) / SudocSudocFranceF

Etudes préliminaires sur la production d'acides gras cyclopropanes, par génie génétique, dans les embryons de lin

Les acides gras cycliques forment après une hydrogénation des acides gras méthylés qui confèrent des propriétés lubrifiantes aux huiles végétales. Pour produire des acides gras cycliques dans les graines de lin, le gène Ec-cfas codant pour l'acide gras cyclopropane synthase pourrait être exprimé sous le contrôle d'un promoteur graine-spécifique, le promoteur napin ou le promoteur At-FAEl. La transformation génétique du lin a d'abord été adaptée aux cultivars Oliver et Barbara. Les efficacités de transformation sont restées faibles (<1% ) mais 16 lignées transgéniques ont été régénérées. Ensuite, la fonctionnalité des deux promoteurs a été étudiée via le gène gus. Le promoteur At-FAE1 montre une activité maximale dans les embryons âgés de 16 à 18 jours. Enfin, l'activité de la protéine Ec-CFA a été montrée chez Arabidopsis par la production d'acides gras cyclopropanes. Chez le lin, la synthèse de ces acides gras inhabituels doit dépendre de facteurs à la fois génétiques et métaboliques.Cyclic fatty acids form after hydrogenation of carbon chains methyl-branched fatty acids conferring excellent lubricating properties on vegetable oils. ln order to produce cyclic fatty acids in linseed, the Ec-cfas gene encoding a fatty acid cyclopropan synthase could be expressed under the control of seed-specific promoter, the napin promoter or the At-FAE1 promoter. First, flax transformation was adapted to cultivars Barbara and Oliver. Whereas the efficiencies of genetic transformation remain low (<1%), 16 transgenic lines were regenerated. Then, the functionality of both promoters was studied using the gus gene. Both promoters specifically expressed transgene in embryos. The At-FAE1 promoter showed a maximal activity in 16 to 18 day-old embryos. Finally, the activity of Ec-CFA protein was showed in Arabidopsis by the production of cyclopropan fatty acids. In linseed, the synthesis of such unusual fatty acids could depend on various genetic as well as metabolic factors.COMPIEGNE-BU (601592101) / SudocSudocFranceF

Biodiversity of lipid species – Benefit for nutrition and effects on health

International audienceEditorial Biodiversity of lipid species e Benefit for nutrition and effects on health This special issue of Biochimie gathers sixteen contributions, mainly combining reviews and research papers, concerning the widespread nutritional problems associated with high-fat diet. The main scientific subjects discussed in this special issue are fatty acids (FAs) and lipid biodiversity in the context of their physiological role within cells, covering various areas of common interest linked to the exploitation of this diversity. This diversity has a major impact on different cellular processes such as transport, metabolism , adaptation, inflammation, etc. To illustrate this topic, this special edition has been organized by themes (1) Unusual FAs and lipid species with interesting physiological effects, (2) Lipids and inflammatory mechanisms e Diseases and prevention, (3) Lipids and nutrition/Lipids and nutraceutic e food and feed and (4) Contributions of lipidomics, metabolomics and fluxomics to knowledge in lipid production and nutrition. It would be of great interest for developing a healthier future diet to gain a better understanding and a deeper knowledge of the potential of lipid species and their drivatives, shedding light on the relationship between FA structures and their physicochemical and therapeutic properties. In this special issue, several contributions are focused on the impact of these lipids on disease and health, and on the development of new strategies for the characterization of lipid structures, using innovative and emerging technologies, such as lipidomics, metabolomics and fluxomics. Benefits to the quality of nutrition and recommendations for adapting diet so as to counter chronic pathologies are presented together with various applications in biotechnology, pharmacology and nutrition. Unusual fatty acids and lipid species with interesting physiological roles It is well known that the plant kingdom provides a deep reservoir of novel FAs, many with structures that confer health-promoting properties. This large diversity of FA structures, found not only in plants but also in algae, fungi, bacteria, and other organisms is an opportunity to identify new bioactive lipids, to discover specific biological activities and to investigate their physiological effects on human health. For example, some specific structures such as those of two essential unsaturated FAs (u6 and u3) act as precursors of very long-chain polyunsaturated FAs (VLC-PUFAs) involved in many signaling molecules of complex inflammatory processes in humans. Furthermore, this great diversity of structures of lipids and FAs conditions the nutritional quality of our food by playing on the composition of oils, and thereby on their functional properties. In addition and on the same theme, other compounds contributing to health-promotion and functionality, such as a-tocopherol, an essential nutrient (vitamin E) and chemical antioxidant helping to stabilize polyunsaturated FAs are described. The two first contributions provide an inventory of the different lipid and FA structures (GLA, SDA, EPA, DHA, u7, …) found in plants and microalgae, detailing mechanisms of their synthesis in the producers , their contributions as sources of precursors for human health, and their therapeutic effects in human diseases such as cancers , neurological disorders, diabetes, cardiovascular diseases and renal dysfunction. The third article is dedicated to a specific and unusual phospholipid (Bis(monoacylglycero)-phosphate-BMP) enriched in polyunsaturated FAs and located in the endolysosomal compartments. This BMP molecule was proposed as a new lipid diagnostic biomarker of drug-induced lysosomal dysfunction in humans. It has also been suggested that specific lipids (glycosphin-golipids, galactosyl-, glucosyl-and phosphoethanolamine-ceramide), might play crucial roles in the structure and function of myelin. From this perspective, an overview of recent advances in biotechnological tools helping in the creation of new specialty lipids used in generating vegetable oils with improved functionality and/or health-promoting FAs is also given. The utility of these innovative technologies for food and feed applications, higher nutritional value and nutraceutical markets is mentioned. Lipids and inflammatory mechanisms e Diseases and prevention Lipids and FAs are often cited as responsible for chronic pathol-ogies or involved in a wide variety of diseases (obesity, heart failure, cardiovascular, cancers, …). These disorders are responsible for inflammation which is a coordinated host response that, when self-limited, is protective. However, intense and persistent inflammation processes often cause tissue damage and/or deleterious effects on organs, involving a multitude of cell types, chemical mediators, and interactions. The mediators can efficiently regulate the physiological function of inflammation, if known. Thus there is a real need for detecting lipid mediators in the immediate effector phase and to identify the pathway of their recognition. The development of novel anti-inflammatory drugs and the elaboration of regenerative treatments and preventive strategies could be then rapidly elaborated. It is a prerequisite for initiating reparatory processes to limit host-tissue degradation and to promote regenera-tion and/or treatment. Along this theme, two review articles summarize the latest developments (i) in the role of lipids in oste-oporosis (OP), and (ii) in the possible influence of diet on tumour growth and development. These two presentations underline the presence of specific FAs in OP bones or in cancerous tumours and their changes during the development of these diseases. In both cases, the polyunsaturated usual and unusual FAs used a

Étude comparative du métabolisme des lipides dans les embryons de lin et de colza producteurs d'acides gras inhabituels ou non (modélisation des systèmes)

COMPIEGNE-BU (601592101) / SudocSudocFranceF

MISE EN PLACE DU SYSTEME DE RECOMBINAISON SITE-SPECIFIQUE FLP/FRT CHEZ LE TABAC (ETUDES PRELIMINAIRES AU CIBLAGE DE GENES)

COMPIEGNE-BU (601592101) / SudocSudocFranceF

Etude et fonctionnalité de promoteurs graines spécifiques de lin dans les embryons de plantes en développement (synthèse d'acides gras inhabituels dans les plantes oléagineuses)

COMPIEGNE-BU (601592101) / SudocSudocFranceF