No description available.

Cuticular wax is a component of the plant cuticle, the lipid barrier which covers the surface of above ground primary plant organs and plays important protective roles. The isolation of wax deficient mutants from Arabidopsis and other plants resulted in identification and isolation of genes required for wax deposition, and broadened our knowledge of this process in plants. To identify additional components involved in cuticular wax production, I investigated the role of the XTC1 gene, defective in the xtcl (extra cotyledon 1) mutant. This mutant was reported to have reduced levels of cuticular wax on its inflorescence stems and accumulate a large number of oil bodies in the primordia of its extra cotyledons. Stem wax extraction and gas chromatography analysis showed that the total xtcl stem wax is decreased 3-fold in comparison to the wild type, and that all wax components were reduced to a similar extent. Compositional analyses of leaf and seed fatty acids demonstrated that saturated fatty acid content was decreased by around 55%, and unsaturated fatty acid content was approximately 20% lower in xtcl mutants. A detailed examination of xtcl seeds revealed seed deformities, altered seed coat permeability and defective seed mucilage extrusion. Positional cloning of the XTC1 gene resulted in the discovery that it is identical to FATB, an already characterized gene known to encode the fatty acid thioesterase B. The FATB enzyme releases saturated free fatty acids (C16:0and C18:0) from ACP in the plastid and allows their export across the plastid envelope. Analysis of FATB gene expression pattern showed that FATB is transcribed ubiquitously in all tissues and in different development stages. It is therefore not surprising that FATB disruption results in multiple lipid associated phenotypes, including decreased cuticular wax amounts and altered fatty acid compositions of leaves and seeds. Additional phenotypes caused by mutations in FATB that affect embryo and seed development and lead to appearance of extra cotyledons, altered permeability of the seed coat and defective seed mucilage extrusion are difficult to explain at present.

Cuticular wax is a component of the plant cuticle, the lipid barrier which covers the surface of above ground primary plant organs and plays important protective roles. The isolation of wax deficient mutants from Arabidopsis and other plants resulted in identification and isolation of genes required for wax deposition, and broadened our knowledge of this process in plants. To identify additional components involved in cuticular wax production, I investigated the role of the XTC1 gene, defective in the xtcl (extra cotyledon 1) mutant. This mutant was reported to have reduced levels of cuticular wax on its inflorescence stems and accumulate a large number of oil bodies in the primordia of its extra cotyledons. Stem wax extraction and gas chromatography analysis showed that the total xtcl stem wax is decreased 3-fold in comparison to the wild type, and that all wax components were reduced to a similar extent. Compositional analyses of leaf and seed fatty acids demonstrated that saturated fatty acid content was decreased by around 55%, and unsaturated fatty acid content was approximately 20% lower in xtcl mutants. A detailed examination of xtcl seeds revealed seed deformities, altered seed coat permeability and defective seed mucilage extrusion. Positional cloning of the XTC1 gene resulted in the discovery that it is identical to FATB, an already characterized gene known to encode the fatty acid thioesterase B. The FATB enzyme releases saturated free fatty acids (C16:0and C18:0) from ACP in the plastid and allows their export across the plastid envelope. Analysis of FATB gene expression pattern showed that FATB is transcribed ubiquitously in all tissues and in different development stages. It is therefore not surprising that FATB disruption results in multiple lipid associated phenotypes, including decreased cuticular wax amounts and altered fatty acid compositions of leaves and seeds. Additional phenotypes caused by mutations in FATB that affect embryo and seed development and lead to appearance of extra cotyledons, altered permeability of the seed coat and defective seed mucilage extrusion are difficult to explain at present.

No description available.

The <i>de novo</i> formation of long-chain fatty acids and the reduction of long-chain fatty acids to the corresponding fatty alcohol were studied in the calanoid copepod <i>Calanus finmarchicus (Calanus</i>) and the fresh-water fish, <i>Trichogaster trichopterus</i> (the gourami). <i>De novo</i> biosynthesis of fatty acids by the enzyme fatty acid synthase (FAS) was localised in the 6.3 x 10⁶g-min supernatant ('cytosolic' fraction) of homogenates of whole <i>Calanus</i> and was characteristic of a Type 1 multienzyme complex. The formation of fatty acids required the presence of acetyl-CoA, malonyl-CoA and was specific for NADPH as the reductant. The main products of the reaction were the saturated long-chain fatty acids stearic acid and palmitic acid, accounting for 54% and 25% of the total fatty acid product, respectively. The alcohol-forming enzyme, NADPH-fatty acyl-CoA oxidoreductase, from both <i>Calanus</i> the gourami roe was membrane-associated. Differential ultracentrifugation showed that a 6.3 x 10⁶g-min pellet (the 'particulate' fraction) was most active in the formation of long-chain fatty acohols. The specific activity of the enzyme in the gourami roe particulate fraction was over 100-fold higher than that in the <i>Calanus</i> particulate fraction. Both systems required the presence of an acyl-CoA generating system in the form of exogenous CoASH, ATP and Mg⁺⁺. The reaction was specific for NADPH as the reductant in the case of the gourami roe system. However, NADH substituted for NADPH in the <i>Calanus</i> system. Palmitic acid, in the presence of an acyl-CoA generating system, was the most effective substrate with the 18:0, 18:1 and 22:1 substrates giving progressively lower activities.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1940. / Typescript. Includes abstract and vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 94-140).

Thesis (M.F.A.)--The University of North Carolina at Greensboro, 2009. / Directed by Mariam Stephan; submitted to the Dept. of Art. Title from PDF t.p. (viewed May 5, 2010).

Cuticular wax is a component of the plant cuticle, the lipid barrier which covers the surface of above ground primary plant organs and plays important protective roles. The isolation of wax deficient mutants from Arabidopsis and other plants resulted in identification and isolation of genes required for wax deposition, and broadened our knowledge of this process in plants. To identify additional components involved in cuticular wax production, I investigated the role of the XTC1 gene, defective in the xtcl (extra cotyledon 1) mutant. This mutant was reported to have reduced levels of cuticular wax on its inflorescence stems and accumulate a large number of oil bodies in the primordia of its extra cotyledons. Stem wax extraction and gas chromatography analysis showed that the total xtcl stem wax is decreased 3-fold in comparison to the wild type, and that all wax components were reduced to a similar extent. Compositional analyses of leaf and seed fatty acids demonstrated that saturated fatty acid content was decreased by around 55%, and unsaturated fatty acid content was approximately 20% lower in xtcl mutants. A detailed examination of xtcl seeds revealed seed deformities, altered seed coat permeability and defective seed mucilage extrusion. Positional cloning of the XTC1 gene resulted in the discovery that it is identical to FATB, an already characterized gene known to encode the fatty acid thioesterase B. The FATB enzyme releases saturated free fatty acids (C16:0and C18:0) from ACP in the plastid and allows their export across the plastid envelope. Analysis of FATB gene expression pattern showed that FATB is transcribed ubiquitously in all tissues and in different development stages. It is therefore not surprising that FATB disruption results in multiple lipid associated phenotypes, including decreased cuticular wax amounts and altered fatty acid compositions of leaves and seeds. Additional phenotypes caused by mutations in FATB that affect embryo and seed development and lead to appearance of extra cotyledons, altered permeability of the seed coat and defective seed mucilage extrusion are difficult to explain at present. / Science, Faculty of / Botany, Department of / Graduate

[pt] Deposição de parafinas de alto peso molecular nas paredes internas de linhas submarinas de produção e transporte é um dos problemas críticos encontrados pela indústria de petróleo. O acúmulo de material depositado pode ocasionar um aumento na potência de bombeamento requerida, diminuição da vazão ou mesmo o bloqueio completo da linha com conseqüente perda de produção e de investimentos. O presente trabalho realizou uma análise detalhada da literatura sobre deposição de parafina onde concluiu-se que não existe evidência experimental suficiente para definir qual o mecanismo básico responsável pela deposição dos cristais de parafina. Baseado no resultado da revisão bibliográfica foram realizados estudos experimentais e simulações numéricas sobre a deposição de parafina no interior de dutos. O trabalho foi direcionado para a condução de estudos de caráter fundamental onde buscou-se, através de experimentos simples, tentar contribuir para o melhor entendimento dos mecanismos de deposição de parafina. Experimentos com deposição em cavidades contendo fluido estagnado e em escoamento laminar produziram resultados para a evolução temporal e espacial da frente de deposição ainda não disponíveis na literatura. O modelo numérico puramente difusivo proposto no presente trabalho para deposição em cavidades com fluido estagnado, subestima os valores de espessura de depósito quando comparados com os valores experimentais observados. As observações realizadas não foram suficientes para corroborar a hipótese que a deposição de parafina é devida somente ao mecanismo de difusão molecular. / [en] Deposition of high molecular weight paraffin on the inner wall of subsea production and transportation pipelines continues to be a critical operational problems faced by the petroleum industry. The accumulation of the deposited material on the inner wall of the lines may lead to increased pumping power, decreased flow rate or even to the total blockage of the line, with loss of production and capital investment. In the present work a critical review of the literature on wax deposition was conducted leading to the conclusion that there is not enough experimental evidence to determine which are the relevant mechanisms responsible for wax deposition. Based on the conclusions of the literature search, experimental studies and numerical simulations were conducted. The focus of the work was on simple, basic studies that were able to contribute to the understanding of the relative importance of the deposition mechanisms. The experiments on deposition cavities containing stagnant fluids and in laminar flow through channels yielded temporal and spatial distributions of paraffin deposits not yet available. A molecular-diffusion-based model developed underestimated the deposit thickness for the stagnant cavity. The results obtained were not sufficient to corroborate the hyphotesis that the wax deposition process is controlled by molecular diffusion.

No description available.