Search results for "Ellul"
showing 10 items of 7037 documents
Evidence for a geranyl-diphosphate synthase located within the plastids of Vitis vinifera L. cultivated in vitro
1992
Intact plastids from cell suspensions of Vitis vinifera L. cv. Muscat de Frontignan, free of detectable contamination by other particles as judged by the distribution of organelle-specific marker enzymes and by electron microscopy, exhibit geranyl-diphosphate synthase activity (EC 2.5.1.1). This synthase activity remains stable after tryptic digestion of unlysed organelles and is enhanced by plastid disruption. We conclude that the enzyme is located within the organelle. The possibility of an isopentenyl diphosphate/dimethylallyl diphosphate translocating system which would play a major role in the regulation of monoterpene metabolism is discussed.
Natural Selection Fails to Optimize Mutation Rates for Long-Term Adaptation on Rugged Fitness Landscapes
2008
The rate of mutation is central to evolution. Mutations are required for adaptation, yet most mutations with phenotypic effects are deleterious. As a consequence, the mutation rate that maximizes adaptation will be some intermediate value. Here, we used digital organisms to investigate the ability of natural selection to adjust and optimize mutation rates. We assessed the optimal mutation rate by empirically determining what mutation rate produced the highest rate of adaptation. Then, we allowed mutation rates to evolve, and we evaluated the proximity to the optimum. Although we chose conditions favorable for mutation rate optimization, the evolved rates were invariably far below the optimu…
Evidence for specific, high-affinity binding sites for a proteinaceous elicitor in tobacco plasma membrane
1995
Abstract Binding of cryptogein, a proteinaceous elicitor, was studied on tobacco plasma membrane. The binding of the [125I]cryptogein was saturable, reversible and specific with an apparent Kd of 2 nM. A single class of cryptogein binding sites was found with a sharp optimum pH for binding at about pH 7.0. The high-affinity correlates with cryptogein concentrations required for biological activity in vivo.
Comparison of the effects of cryptogein and oligogalacturonides on tabacco cells and evidence of different forms of desensitization induced by these …
1998
Abstract The effects of cryptogein and oligogalacturonides (OGs) were compared on tobacco cells by measuring calcium influx and calcium-dependent responses including extracellular alkalinization and H 2 O 2 production. The main difference is the higher calcium influx and the sustained H 2 O 2 production induced by cryptogein compared to OGs. Amplitude and duration of calcium signalling triggered by cryptogein or OGs may explain the necrotic effect of cryptogein, and the absence of necrosis in tobacco plants treated with OGs. We used induction of alkalinization and H 2 O 2 production to investigate cryptogein effects after a first treatment with cryptogein or OGs, and reciprocally. Results s…
Potential of an exploitation of acid-tolerant antimicrobial microorganisms evolving enzyme systems for the utilization of dairy by-products and ligno…
2016
Introduction Bioproduction of optically pure lactic acid (LA) has roused interest in the recent years due to its potential application in a wide range of fields, and there is a significant interest to further development of sustainable and cost-effective process. However, the efficient utilization of agro-industrial wastes for LA production still causes considerable challenges. The biotechnological LA production within the targeted cost still required the development of high-performance LA-producing microorganisms and the lowering of the costs of raw materials and fermentation process. Cheap biomass, such as starchy and cellulosic agricultural residues or by-products from the food industry,…
Involvement of osmotic cell shrinkage on the proton extrusion rate in Saccharomyces cerevisiae
2001
Saccharomyces cerevisiae has been subjected to hyperosmotic shocks by using permeating (sorbitol, xylitol, glycerol, NaCl) and nonpermeating (PEG 600) solutes. The proton extrusion rate decreased as the osmotic pressure increased, whichever solute was used. However, the total inhibition of the cellular H+ extrusion depended on the solute used. A total inhibition was observed at about 20 MPa with glycerol, xylitol and sorbitol. With PEG 600, a total inhibition of extracellular acidification was obtained at 8.5 MPa. NaCl, with an extracellular pressure of 37.8 MPa (near saturation), did not completely inhibit the extracellular acidification. These results showed that the total inhibition of p…
Kinetic studies on protoporphyrinogen oxidase inhibition by diphenyl ether herbicides
1991
Diphenyl ethers (DPEs) and related herbicides are powerful inhibitors of protoporphyrinogen oxidase, an enzyme involved in the biosynthesis of haems and chlorophylls. The inhibition kinetics of protoporphyrinogen oxidase of various origins by four DPEs, (methyl)-5-[2-chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid (acifluorfen and its methyl ester, acifluorfen-methyl), methyl-5-[2-chloro-4-(trifluoromethyl) phenoxy]-2-chlorobenzoate (LS 820340) and methyl-5-[2-chloro-5-(trifluoromethyl)phenoxy]-2-nitrobenzoic acid (RH 5348), were studied. The inhibitions of the enzymes from maize (Zea mays) mitochondrial and etiochloroplastic membranes and mouse liver mitochondrial membranes were com…
NADPH Oxidase-Mediated Reactive Oxygen Species Production: Subcellular Localization and Reassessment of Its Role in Plant Defense
2009
International audience; Chemiluminescence detection of reactive oxygen species (ROS) triggered in tobacco BY-2 cells by the fungal elicitor cryptogein was previously demonstrated to be abolished in cells transformed with an antisense construct of the plasma membrane NADPH oxidase, NtrbohD. Here, using electron microscopy, it has been confirmed that the first hydrogen peroxide production occurring a few minutes after challenge of tobacco cells with cryptogein is plasma membrane located and NtrbohD mediated. Furthermore, the presence of NtrbohD in detergent-resistant membrane fractions could be associated with the presence of NtrbohD-mediated hydrogen peroxide patches along the plasma membran…
Systematic analysis of specific and nonspecific auxin effects on endocytosis and trafficking.
2021
Abstract The phytohormone auxin and its directional transport through tissues are intensively studied. However, a mechanistic understanding of auxin-mediated feedback on endocytosis and polar distribution of PIN auxin transporters remains limited due to contradictory observations and interpretations. Here, we used state-of-the-art methods to reexamine the auxin effects on PIN endocytic trafficking. We used high auxin concentrations or longer treatments versus lower concentrations and shorter treatments of natural indole-3-acetic acid (IAA) and synthetic naphthalene acetic acid (NAA) auxins to distinguish between specific and nonspecific effects. Longer treatments of both auxins interfere wi…
Comparison of binding properties and early biological effects of elicitins in tobacco cells
1998
Abstract Elicitins are a family of small proteins secreted by Phytophthora species that have a high degree of homology and elicit defense reactions in tobacco (Nicotiana tabacum). They display acidic or basic characteristics, the acidic elicitins being less efficient in inducing plant necrosis. In this study we compared the binding properties of four elicitins (two basic and two acidic) and early-induced signal transduction events (Ca2+ influx, extracellular medium alkalinization, and active oxygen species production). The affinity for tobacco plasma membrane-binding sites and the number of binding sites were similar for all four elicitins. Furthermore, elicitins compete with one another fo…