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Showing papers by "Institut national de la recherche agronomique published in 1995"


Journal ArticleDOI
TL;DR: The genetic information present in the plant mitochondrial DNA and chloroplast DNA is of great interest in phylogeny and in population genetics, largely because of the non-mendelian mode of inheritance of these genomes.
Abstract: The genetic information present in the plant mitochondrial DNA (mtDNA) and chloroplast DNA (cpDNA) is of great interest in phylogeny and in population genetics, largely because of the non-mendelian mode of inheritance of these genomes. The circular cpDNA molecule has been shown to be highly conserved in structure Palmer & Stein 1986). This has led to the design of pairs of 'universal' primers which can amplify noncoding regions separating two coding sequences in most land plants (Taberlet et al. 1991). Such non-coding sequences can then be explored (through sequencing or simply by using a variety of restriction enzymes) in order to detect informative polymorphism at a variety of taxonomic levels. The efficiency of this approach has already been demonstrated in phylogenetic and population genetic studies (e.g. Arnold et nl. 1991). However, only a limited number of such universal chloroplast primers have been described so far, whereas no mitochondrial primers seem to have been described. Though the substitution rate of plant mitochondrial DNA genes is even smaller than that of chloroplast genes (Wolfe et nl. 1987), making it easy to identify conserved coding sequences to anchor primers, the amazing lability of the organisation and size of this genome Palmer 1992) is a serious limitation when non-coding sequences need to be amplified. Here we descr i i mitochondrial universal primers, together with additional chloroplast universal primers, which we expect to be useful in a variety of studies of the genetic variability of both organelle genomes of land plants.

1,173 citations


Journal ArticleDOI
11 Aug 1995-Science
TL;DR: The Arabidopsis thaliana RPM1 gene enables dual specificity to pathogens expressing either of two unrelated Pseudomonas syringae avr genes, and encodes a protein sharing molecular features with recently described single-specificity R genes.
Abstract: Plants can recognize pathogens through the action of disease resistance (R) genes, which confer resistance to pathogens expressing unique corresponding avirulence (avr) genes. The molecular basis of this gene-for-gene specificity is unknown. The Arabidopsis thaliana RPM1 gene enables dual specificity to pathogens expressing either of two unrelated Pseudomonas syringae avr genes. Despite this function, RPM1 encodes a protein sharing molecular features with recently described single-specificity R genes. Surprisingly, RPM1 is lacking from naturally occurring, disease-susceptible Arabidopsis accessions.

934 citations


Journal ArticleDOI
TL;DR: Physical and sensory quality of fish flesh were little affected by dietary treatments, and plasma vitellogenin levels were not significantly affected by the dietary levels of protein from soybean.

783 citations


Journal ArticleDOI
TL;DR: The great variability in behavior and in physiological patterns generally associated with emotional reactivity is described, suggesting that fearfulness could be considered a basic feature of the temperament of each individual, one that predisposes it to respond similarly to a variety of potentially alarming challenges but is nevertheless continually modulated during development by the interaction of genetic traits of reactivity with environmental factors, particularly in the juvenile period.
Abstract: Persistence of individual differences in animal behavior in reactions to various environmental challenges could reflect basic divergences in temperament, which might be used to predict details of adaptive response. Although studies have been carried out onfear and anxiety in various species, including laboratory, domestic and wild animals, no consistent definition offearfulness as a basic trait of temperament has emerged. After a classification of the events that may produce a state of fear, this article describes the great variability in behavior and in physiological patterns generally associated with emotional reactivity. The difficulties of proposing fearfulness - the general capacity to react to a variety of potentially threatening situations - as a valid basic internal variable are then discussed. Although there are many studies showing covariation among the psychobiological responses to different environmental challenges, other studies find no such correlations and raise doubts about the interpretation offearfulness as a basic personality trait. After a critical assessment of methodologies used in fear and anxiety studies, it is suggested that discrepancies among results are mainly due to the modulation of emotional responses in animals, which depend on numerous genetic and epigenetic factors. It is difficult to compare results obtained by different methods from animals reared under various conditions and with different genetic origins. The concept offearfulness as an inner trait is best supported by two kinds of investigations. First, an experimental approach combining ethology and experimental psychology produces undeniable indicators of emotional reactivity. Second, genetic lines selectedfor psychobiological traits prove useful in establishing relationships between behavioral and neuroendocrine aspects of emotional reactivity. It is suggested that fearfulness could be considered a basic feature of the temperament of each individual, one that predisposes it to respond similarly to a variety of potentially alarming challenges, but is nevertheless continually modulated during development by the interaction of genetic traits of reactivity with environmentalfactors, particularly in the juvenile period. Such interaction may explain much of the interindividual variability observed in adaptive responses.

709 citations


Proceedings Article
20 Aug 1995
TL;DR: A simple algebraic framework is considered, related to Partial Constraint Satisfaction, which subsumes most of these proposals and is used to characterize existing proposals in terms of rationality and computational complexity.
Abstract: In order to deal with over-constrained Constraint Satisfaction Problems, various extensions of the CSP framework have been considered by taking into account costs, uncertainties, preferences, priorities...Each extension uses a specific mathematical operator (+, max...) to aggregate constraint violations. In this paper, we consider a simple algebraic framework, related to Partial Constraint Satisfaction, which subsumes most of these proposals and use it to characterize existing proposals in terms of rationality and computational complexity. We exhibit simple relationships between these proposals, try to extend some traditional CSP algorithms and prove that some of these extensions may be computationally expensive.

697 citations


Journal ArticleDOI
TL;DR: Findings indicate that inIB is required for entry of L. monocytogenes into hepatocytes, but not into intestinal epithelial cells; inIB encodes a surface protein; and internalin plays a role for entry into some hepatocyte cell lines.
Abstract: The intracellular bacterium Listeria monocytogenes can invade several types of normally non-phagocytic cells. Entry into cultured epithelial cells requires the expression of inIA, the first gene of an operon, comprising two genes: inIA, which encodes internalin, an 800-amino-acid protein, and inIB, which encodes a 630-amino-acid protein. Several genes homologous to inIA are detected in the genome of L. monocytogenes; InIB is one of them. We have assessed the role of inIB in invasiveness of L. monocytogenes by constructing isogenic chromosomal deletion mutants in the inIAB locus. Our findings indicate that: i) inIB is required for entry of L. monocytogenes into hepatocytes, but not into intestinal epithelial cells; ii) inIB encodes a surface protein; iii) internalin plays a role for entry into some hepatocyte cell lines. These results provide the first insight into the cell tropism displayed by L. monocytogenes.

489 citations


Journal ArticleDOI
TL;DR: The results indicate that both genomes are maternally inherited, an observation which agrees with the commonly observed pattern of inheritance in angiosperms and confirms that both chloroplast DNA and mitochondrial DNA can be used as a source of seed-specific markers for the study of the geographic structure of oaks.
Abstract: The restriction patterns of two chloroplast fragments and one mitochondrial DNA fragment, amplified by PCR with universal primers, were studied to determine the mode of inheritance of these organelles in 143 progeny of five intraspecific crosses in pedunculate oak (Quercus robur L.). The results indicate that both genomes are maternally inherited, an observation which agrees with the commonly observed pattern of inheritance in angiosperms. They confirm that both chloroplast DNA and mitochondrial DNA can be used as a source of seed-specific markers for the study of the geographic structure of oaks. This is the first report of organelle inheritance within the Fagaceae, an important and widespread tree family.

461 citations


Journal ArticleDOI
TL;DR: Thinning enhanced tree growth as a result of a longer growing period due to the absence of summer drought and higher rates of growth and increased inter-tree variability in sap flow density, which was closely related to a leaf area competition index.
Abstract: Summary To quantify the effects of crown thinning on the water balance and growth of the stand and to analyze the ecophysiological modifications induced by canopy opening on individual tree water relations, we conducted a thinning experi ment in a 43-year-old Quercus petraea stand by removing trees from the upper canopy level. Soil water content, rainfall inter ception, sap flow, leaf water potential and stomatal conduc tance were monitored for two seasons following thinning. Seasonal time courses of leaf area index (LAI) and girth increment were also measured. Predawn leaf water potential was significantly higher in trees in the thinned stand than in the closed stand, as a conse quence of higher relative extractable water in the soil. The improvement in water availability in the thinned stand resulted from decreases in both interception and transpiration. From Year 1 to Year 2, an increase in transpiration was observed in the thinned stand without any modification in LAI, whereas changes in transpiration in the closed stand were accompanied by variations in LAI. The different behaviors of the closed and open canopies were interpreted in terms of coupling to the atmosphere. Thinning increased inter-tree variability in sap flow density, which was closely related to a leaf area competi tion index. Stomatal conductance varied little inside the crown and differences in stomatal conductance between the treat ments appeared only during a water shortage and affected mainly the closed stand. Thinning enhanced tree growth as a result of a longer growing period due to the absence of summer drought and higher rates of growth. Suppressed and dominant trees benefited more from thinning than trees in the codomi nant classes.

455 citations



Journal ArticleDOI
TL;DR: In this paper, the PROSPECT leaf optical properties and SAIL reflectance models were coupled and inverted using a set of 96 AVIRIS (Airborne Visible/Infrared Imaging Spectrometer) equivalent spectra gathered in a field experiment on sugar beet plots expressing a large range in leaf area index, chlorophyll concentration, and soil color.

409 citations


Journal ArticleDOI
TL;DR: In this paper, an analysis of the relationship between the flexural behavior of extruded foams and the model of cellular solids with open cavities was performed in the presence of water or water with glycerol.

Journal ArticleDOI
TL;DR: This review focuses on the modern physicochemical methods of structural analysis of lignins, and on the new approaches of molecular biology and genetic engineering applied to lignification.
Abstract: SUMMARY Lignins, which result from the dehydrogenative polymerization of cinnamyl alcohols, are complex heteropolymers deposited in the walls of specific cells of higher plants. Lignins have probably been associated to land colonization by plants but several aspects concerning their biosynthesis, structure and function are still only partially understood. This review focuses on the modern physicochemical methods of structural analysis of lignins, and on the new approaches of molecular biology and genetic engineering applied to lignification. The principles, advantages and limitations of three important analytical tools for studying lignin structure are presented. They include carbon 13 nuclear magnetic resonance, analytical pyrolysis and thioacidolysis. The use of these methods is illustrated by several examples concerning the characterization of grass lignins,‘lignin-like’materials in protection barriers of plants and lignins produced by cell suspension cultures. Our present limited knowledge of the spatio temporal deposition of lignins during cell wall differentiation including the nature of the wall components associated to lignin deposition and of the cross-links between the different wall polymers is briefly reviewed. Emphasis is placed on the phenylpropanoid pathway enzymes and their corresponding genes which are described in relation to their potential roles in the quantitative and qualitative control of lignification. Recent findings concerning the promoter sequence elements responsible for the vascular expression of some of these genes are presented. A section is devoted to the enzymes specifically involved in the synthesis of monolignols: cinnamoyl CoA reductase and cinnamyl alcohol dehydrogenase. The recent characterization of the corresponding cDNAs/genes offers new possibilities for a better understanding of the regulation of lignification. Finally, at the level of the synthesis, the potential involvement of peroxidases and laccases in the polymerization of monolignols is critically discussed. In addition to previously characterized naturally occurring lignin mutants, induced lignin mutants have been obtained during the last years through genetic engineering. Some examples include plants transformed by O-methyltransferase and cinnamyl alcohol dehydrogenase antisense constructs which exhibit modified lignins. Such strategies offer promising perspectives in gaining a better understanding of lignin metabolism and functions and represent a realistic way to improve plant biomass.

Journal ArticleDOI
22 Jun 1995-Nature
TL;DR: Different mutants in Arabidopsisthat are unable to form these two cortical microtubular arrays are described, and surprisingly, the mutations do not affect differentiation patterns: all cell types and organs are in their correct relative positions.
Abstract: IT is generally accepted that polarized cell expansion and the strict control of division plane alignment are prerequisites for ordered spatial development in higher plants(1) This appears to be l

Journal ArticleDOI
TL;DR: The results show that dietary flavonol are recovered in rat plasma as conjugated metabolites in non-negligible concentrations, and that these flavonols may be interesting antioxidant micronutrients with a variety of biological effects.
Abstract: We studied the bioavailability and the plasma transport of flavonols in rats fed quercetin or rutin diets. Wistar rats were fed one of the following purified diets for 10 d: control; 16.4 or 8.2 mmol rutin/kg diet; or 16.4, 8.2 or 4.1 mmol quercetin/kg diet. Flavonol concentrations were determined in plasma, ileal and cecal contents, and feces. In rats fed diets containing 16.4 mmol quercetin or rutin/kg, the concentration of circulating flavonols was approximately 115 mumol/L. Quercetin or rutin administration resulted in similar concentrations of quercetin in cecal contents. By HPLC analysis and beta-glucuronidase/sulfatase treatment, plasma flavonols have been identified as conjugated quercetin itself, or a conjugated form (4.5-fold as abundant) of an aglycone less polar than quercetin. Rats fed quercetin or rutin diets had a green/yellow-colored plasma that exhibited a peak absorbance at 411 nm, vs. 363 or 375 nm for pure rutin or quercetin solutions, respectively. This shift of band I absorption was obtained when pure quercetin was in the presence of albumin or added to a plasma fraction. The bathochromic properties of flavonoids in the presence of albumin are highly dependent on the presence of the C-2/C-3 double bond on the C-ring and are influenced by the degree of B-ring hydroxylation. The existence of intermolecular bonds between albumin and quercetin is supported by in vitro absorbance and fluorescence studies. With human albumin, the fluorescence intensity and the shift of quercetin absorbance increased in parallel to the albumin/quercetin molar ratio. Conjugated diene formation, resulting from Cu(2+)-catalyzed oxidation of human LDL or rat VLDL+LDL was effectively inhibited in vitro by 0.5 mumol/L quercetin. These results show that dietary flavonols are recovered in rat plasma as conjugated metabolites in non-negligible concentrations, and that these flavonols may be interesting antioxidant micronutrients with a variety of biological effects.

Journal ArticleDOI
TL;DR: The results suggest that these oligomers are side-chain constituents of heteroxylans in maize bran and Ferulic acid is probably partly responsible for the insolubility of heterxylans by coupling polysaccharide chains through ferulic acid dimers.

Journal ArticleDOI
TL;DR: Propionate may represent an effective inhibitor of lipid synthesis when acetate is a major source of acetyl-CoA, a situation which is encountered with diets rich in readily-fermentable fibres.
Abstract: In the present study the actual role of propionic acid in the control of fatty acid and cholesterol synthesis was investigated in isolated liver cells from fed rats maintained in the presence of near-physiological concentrations of glucose, glutamine and acetate. Using 3H2O for lipid labelling, propionate appears as an effective inhibitor of fatty acid synthesis and to a lesser extent of cholesterol synthesis, even at the lowest concentration used (0.6 mmol/l). Butyrate is a potent activator of both synthetic pathways, and the activating effect was not counteracted by propionate. Using 1-[14C]acetate, it was observed that propionate at a moderate concentration, or 1 mmol oleate/l, are both very effective inhibitors of 14C incorporation into fatty acid and cholesterol. This incorporation was drastically inhibited when propionate and oleate were present together in the incubation medium. The net utilization of acetate by rat hepatocytes was impaired by propionate, in contrast to oleate. 1-[14C]butyrate was utilized at a high rate for fatty acid synthesis, but to a lesser extent for cholesterol synthesis; both processes were unaffected by propionate. Intracellular citrate concentration was not markedly depressed by propionate, whereas it was strongly elevated by butyrate. In conclusion, propionate may represent an effective inhibitor of lipid synthesis when acetate is a major source of acetyl-CoA, a situation which is encountered with diets rich in readily-fermentable fibres. The present findings also suggest that propionate may be effective at concentrations close to values measured in vivo in the portal vein.

Journal ArticleDOI
TL;DR: It is shown that, at a given locus, there is a unique sample size per population which yields the smallest variance of GST, regardless of the number of populations studied, and the optimal sampling strategy for measuring GST is considered.
Abstract: An extension of Nei's analysis of diversity in a subdivided population is proposed for a haploid locus. The differentiation G STbecomes a natural extension of Wright's F STand generalizes Weir and Cockerham's parameter of co-ancestry by relaxing the assumption of identical correlation for all the alleles. Inter- and intrapopulation variances of the estimated diversities and differentiation are derived. Finally, the optimal sampling strategy for measuring G STwhen a fixed number of individuals can be analysed is considered. It is shown that, at a given locus, there is a unique sample size per population which yields the smallest variance of G ST,regardless of the number of populations studied. These theoretical developments are illustrated with an analysis of chloroplast DNA diversity in a forest tree. The results emphasize the necessity of sampling many populations, rather than many individuals per population, for an accurate measurement of the subdivision of gene diversity at a single locus.

Journal ArticleDOI
TL;DR: In this article, a simple algorithm to retrieve sail moisture and vegetation water content from passive microwave measurements is analyzed, based on a zeroth-order solution of the radiative transfer equations in a vegetation layer.

Journal ArticleDOI
TL;DR: Methanogenic bacteria associated with rumen ciliates were apparently responsible for between 9 and 25% of methanogenesis in rumen fluid.
Abstract: The importance of methanogenic bacteria associated with ciliate protozoa was estimated either by removing protozoa from whole rumen fluid (using defaunated rumen fluid to correct for the effects of centrifugation on bacteria) or by isolating the protozoa. Rumen fluid was withdrawn from sheep inoculated with either Polyplastron multivesiculatum, a co-culture of Isotricha prostoma plus Entodinium spp. or a mixed type B fauna of Entodinium, Eudiplodinium and Epidinium spp. Methanogenesis was highest in rumen fluid containing a mixed protozoal population of the following genera: Entodinium, Eudiplodinium and Epidinium, was lower in defaunated rumen fluid and lowest in rumen fluid containing either I. prostoma plus Entodinium or P. multivesiculatum. Methanogenic bacteria associated with rumen ciliates were apparently responsible for between 9 and 25% of methanogenesis in rumen fluid.

Journal ArticleDOI
TL;DR: Although the lignin composition was consistently modified, theLignin content of the transgenic poplars was similar to that of the controls, and a similar phenotype was observed in brown-midrib mutants of maize and sorghum, known for their altered lignification.
Abstract: Summary Lignin is a polymeric constituent of the cell wall that needs to be removed during the paper making process. Bi-specific caffeic acid/5-hydroxyferulic acid O-methyltransferase (COMT) catalyses the O-methylation of caffeic acid and 5-hydroxyferulic acid to ferulic acid and sinapic acid, respectively. These compounds are intermediates in the biosynthesis of the lignin precursors. Therefore, COMTs are potential target enzymes for reducing the amount, or modifying the composition, of lignin in plants. Different antisense and sense constructs have been expressed of a gene encoding a COMT from poplar (Populus trichocarpa x P. deltoides) in a P. tremula x P. alba clone under the control of the cauliflower mosaic virus 35S promoter. From all analysed transformants, four lines transformed with an antisense construct had a reduced COMT activity. Two showed a 50% reduction of COMT activity, which altered only slightly the monomeric composition. In the two other transformants, the COMT activity was reduced by 95%. In the latter case, the syringyl/ guaiacyl ratio (S/G) was reduced by sixfold (due to a decrease of S and an increase of G), as analysed by thioacidolysis. A new component of lignin, the 5-hydroxyguaiacyl residue, was detected among the thioacidolysis products. Moreover, in contrast to the white/yellow colour of wild-type wood, the xylem of the transgenic lines with a 95% reduction of COMT activity was pale rose. A similar phenotype was observed in brown-midrib mutants of maize and sorghum, known for their altered lignification. Although the lignin composition was consistently modified, the lignin content of the transgenic poplars was similar to that of the controls.

Journal ArticleDOI
TL;DR: The data suggest that a plant metal transporter, which is most likely involved in the transport of copper, has been identified and is associated with an increased sensitivity to copper toxicity.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the linkages which hold heteroxylans in maize bran cell walls and found that linkages to structural cell wall proteins were probably the main cause of heteroxylan insolubility.

Journal ArticleDOI
TL;DR: Data demonstrate the feasibility and the potential benefits of lignin manipulation and show T-DNA genes were shown to be stably integrated into the tobacco genome and to be transmitted to the progeny.
Abstract: Summary The monomeric composition of tobacco lignin has been modified by genetic engineering. Sense or antisense expression of sequences encoding O-methyltransferase (OMT), a lignin biosynthetic enzyme, was shown to modulate enzyme activity. Ten constructs harboring the entire or a partial OMT cDNA were used. Populations of 20 trensgenic plants per construct were analyzed for OMT activity and compared with untransformed controls. As expected, expression of only the full-length sense construct led to an increase in OMT activity. An important reduction of activity was found in a variable number of plantlets from all other transgenic populations but the inhibition was sustained through the adult stage only in plants transformed with the complete cDNA. T-DNA genes were shown to be stably integrated into the tobacco genome and to be transmitted to the progeny. By using gene-specific probes, OMT inhibition in stems was correlated to a parallel disappearance of OMT transcripts originating from both the resident gene and the transgene. In contrast, transgene transcripts were detected in leaf tissues where the resident gene is poorly expressed, thus indicating that relative expression of the two OMT genes controls transcript turnover. In stems of inhibited plants, a marked decrease of syringyl units and the appearance of 5-hydroxy guaiacyl units were demonstrated. These two structural features are also characteristic of natural mutants of maize with an improved digestibility compared with wild lines. These data demonstrate the feasibility and the potential benefits of lignin manipulation.

Journal ArticleDOI
TL;DR: There is a unique sample size per population which yields the best accuracy in estimating FST and FIS, respectively, at a given locus, compared to those obtained under the Hardy-Weinberg assumption.
Abstract: Nei's analysis of diversity at a diploid locus is extended to a population subdivided into a large number of subpopulations. The diversities and the heterozygotes frequency are defined with respect to the total population and unbiasedly estimated in a two-stage random cluster sampling. The fixation indices F IS, F IT andF ST are derived, then inter- and intra-population variances of the estimated parameters are studied. We show that there is a unique sample size per population which yields the best accuracy in estimatingF ST and F IS, respectively, at a given locus. These results are illustrated with an analysis of DNA diversity in a forest tree and compared to those obtained under the Hardy-Weinberg assumption.

Journal ArticleDOI
TL;DR: Since citrinin is a toxic product, it is essential that the production of red pigments as food additives from Monascus spp.

Journal ArticleDOI
TL;DR: Temperature-dependent sex differentiation may occur more frequently in fish than previously thought, despite the presence of functional sex chromosomes, and sex reversal by temperature treatment was confirmed on a genotypic female population.
Abstract: Up to now, temperature sex differentiation has been demonstrated in a single fish species, #Menidia menidia# This study analyzes this hypothesis in #Oreochromis niloticus# Treatments at 36 °C, covering the hormone sensitive period, increased the proportion of males (33% to 81%)The male proportion was affected by treatments starting not later than 13 days after fertilization and lasting 10 days or more Survival rates were not affected by treatments Functional masculinization of genetic females was demonstrated by the sex-ratio analysis of 10 temperature-treated males Sex reversal by temperature treatment was also confirmed on a genotypic female population The response to temperature strongly depends upon the breeding pairs Hight temperatures override sex chromosome influence in #Oreochromis niloticus# Therefore, #Oreochromis niloticus# sex is determined by genetic factors, temperature level, and genotype-temperature interactions Temperature-dependent sex differentiation may occur more frequently in fish than previously thought, despite the presence of functional sex chromosomes (Resume d'auteur)

Journal ArticleDOI
TL;DR: Moderate changes in leaf Fe content have a dramatic effect on plant metabolism, indicating that cellular Fe concentrations must be finely regulated to avoid cellular damage most probably because of oxidative stress induced by Fe.
Abstract: Fe excess is believed to generate oxidative stress. To contribute to the understanding of Fe metabolism, Fe excess was induced in Nicotiana plumbaginifolia grown in hydroponic culture upon root cutting. Toxicity symptoms leading to brown spots covering the leaf surface became visible after 6 h. Photosynthesis was greatly affected within 12 h; the photosynthetic rate was decreased by 40%. Inhibition of photosynthesis was accompanied by photoinhibition, increased reduction of photosystem II, and higher thylakoid energization. Fe excess seemed to stimulate photorespiration because catalase activity doubled. To cope with cellular damage, respiration rate increased and cytosolic glucose-6-phosphate dehydrogenase activity more than doubled. Simultaneously, the content of free hexoses was reduced. Indicative of generation of oxidative stress was doubling of ascorbate peroxidase activity within 12 h. Contents of the antioxidants ascorbate and glutathione were reduced by 30%, resulting in equivalent increases of dehydroascorbate and oxidized glutathione. Taken together, moderate changes in leaf Fe content have a dramatic effect on plant metabolism. This indicates that cellular Fe concentrations must be finely regulated to avoid cellular damage most probably because of oxidative stress induced by Fe.

Journal ArticleDOI
TL;DR: In vitro fermentations with inocula made from human faeces and from rat caecal contents gave similar results and there was a close correspondence between the data obtained in the present experiment and those previously published in in vivo studies in the rat.
Abstract: Five European laboratories tested a simple in vitro batch system for dietary fibre fermentation studies. The inoculum was composed of fresh human faeces mixed with a carbonate-phosphate buffer complex supplemented with trace elements and urea. Five dietary fibre sources (cellulose, sugarbeet fibre, soyabean fibre, maize bran and pectin) were used by each laboratory on three occasions to determine pH, residual non-starch polysaccharides (NSP) and short-chain fatty acid production during fermentation. Cellulose and maize bran degradabilities were very low (7.2(SE 10.8) and 6.2 (SE 9.1)% respectively after 24 h), whereas pectin and soyabean fibre were highly degraded (97.4 (SE 4.4) and 91.1 (SE 3.4)% respectively after 24 h). Sugarbeet fibre exhibited an intermediate level of degradability (59.5 (SE 14.9)%). Short-chain fatty acid production was closely related to NSP degradation (r 0.99). Although each variable was ranked similarly by all laboratories, some differences occurred with respect to absolute values. However, the adaptation of donors to the experimental substrates was not an influential factor. Interlaboratory differences could be reduced either by adding less substrate during incubations or using less-diluted inocula. In vitro fermentations with inocula made from human faeces and from rat caecal contents gave similar results. There was a close correspondence between the data obtained in the present experiment and those previously published in in vivo studies in the rat using the same fibres. The in vitro batch system tested during the present study provides a rapid means of obtaining quantitative estimates of the fermentation and the estimation of the energy content of new sources of dietary fibre.

Journal ArticleDOI
01 Jan 1995-Lait
TL;DR: The role of polysaccharides exocellulaires dans the fabrication of the laits fermentes is discussed in this paper, where it is shown that their presence is indispensable for obtenir a texture convenable du produit.
Abstract: Les bacteries Gram + productrices d'exopolysaccharides les plus etudiees sont les bacteries lactiques utilisees dans la fabrication de divers laits fermentes, telles que Streptococcus thermophilus, Lactobacillus delbrueckii ssp bulgaricus et Lactococcus lactis ssp cremoris. Le role des polysaccharides exocellulaires dans la fabrication des laits fermentes, et en particulier du yaourt, n'est plus a demontrer. Il est en effet reconnu que leur presence est indispensable pour obtenir une texture convenable du produit. Un certain nombre de souches de ces bacteries produisent des heteropolysaccharides constitues d'un enchainement lineaire ou ramifie d'un petit nombre de sucres (1 a 7) appele unite repetitive. Ces unites, par enchainement lineaire ou ramifie d'une centaine a plusieurs milliers, forment le polysaccharide de poids moleculaire souvent tres eleve (1 a 2 x 10 6 ). Les bacteries propioniques sont egalement capables de produire des EPS, mais les recherches dans ce domaine sont moins avancees. Toutefois, la comparaison des connaissances sur les bacteries lactiques d'interet laitier et les bacteries propioniques permet de degager un certain nombre de similitudes. En effet, les conditions de culture (temperature, duree d'incubation) et la composition du milieu (source d'azote et de carbone) ont une influence considerable sur la production des EPS et leur composition en monosaccharides. Les monosaccharides les plus frequemment identifies dans les polysaccharides exocellulaires produits par les bacteries propioniques sont le glucose, le galactose, le mannose et parfois le rhamnose ou le fucose. En revanche, les poids moleculaires de l'ordre de 200 a 5 000 sont nettement inferieurs a ceux des exopolysaccharides produits par les bacteries lactiques. La capacite des bacteries lactiques de produire des polymeres est une propriete extremement instable. Elle est portee par des plasmides de taille variable dans le cas des bacteries lactiques mesophiles, alors que celle des bacteries lactiques thermophiles semble sous controle chromosomique. Il est connu que les bacteries propioniques contiennent des plasmides (Rehberger et Glatz, 1990), mais en absence de travaux dans ce domaine, il n'est pas possible pour l'instant de lier la capacite de produire des EPS de ces bacteries a la presence d'un ou plusieurs plasmides.

Journal ArticleDOI
TL;DR: It is concluded that AM fungal inoculation influenced processes in the root system at different levels, but not all effects were due to improved P nutrition or increased physiological age.
Abstract: We compared root system morphogenesis of micropropogated transplants of Prunus cerasifera L. inoculated with either of the arbuscular mycorrhizal (AM) fungi Glomus mosseae or Glomus intraradices or with the ericoid mycorrhizal species Hymenoscyphus ericae. All plants were grown in sand culture, irrigated with a nutrient solution that included a soluble source of phosphorus, for 75 days after transplanting. Arbuscular mycorrhizal colonization increased both the survival and growth (by over 100%) of transplants compared with either uninoculated controls or transplants inoculated with H. ericae. Arbuscular mycorrhizal colonization increased root, stem and leaf weights, leaf area, root length and specific leaf area, and it decreased root length/leaf area ratio, root/shoot weight ratio and specific root length. Both uptake of phosphorus and its concentration in leaves were increased by AM infection, although the time course of the relationships between intensity of AM infection and P nutrition were complex and suggested a role for factors other than nutrition. The time course for the development of infection varied. It was most rapid with G. mosseae, but it was ultimately higher with G. intraradices. None of the treatments significantly affected the lengths of adventitious roots or the first-, second- or third-order laterals that developed from them. Arbuscular mycorrhizal colonization increased the intensity of branching in all root orders with the effect being most obvious on first-order lateral roots where the number of branches increased from under 100 to over 300 brances m(-1). As a result, although first-order laterals made up 55% of the root systems of control plants, the comparable value was 36% in AM-infected plants. In contrast, second-order laterals represented 25% of control root systems, but 50% of AM-colonized root systems. Glomus intraradices but not G. mosseae increased root diameter. Anatomical studies revealed no changes in the overall form of the root tip, although there were changes in the diameter of the root cap, cell numbers and cell size. Hymenoscyphus ericae increased the duration of the metaphase index. Both AM fungal treatments increased the concentrations of soluble proteins in root extracts and modified the protein profiles by the elimination and addition of protein bands detected by PAGE analysis. We conclude that AM fungal inoculation influenced processes in the root system at different levels, but not all effects were due to improved P nutrition or increased physiological age.