Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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The relationship between the presence of antibodies and direct detection of Toxoplasma gondii in slaughtered calves and cattle in four European countries
Opsteegh, M. ; Spano, F. ; Aubert, D. ; Balea, A. ; Burrells, A. ; Cherchi, S. ; Cornelissen, J.B.W.J. ; Dam-Deisz, C. ; Guitian, J. ; Györke, A. ; Innes, E.A. ; Katzer, F. ; Limon, G. ; Possenti, A. ; Pozio, E. ; Schares, G. ; Villena, I. ; Wisselink, H.J. ; Giessen, J.W.B. van der - \ 2019
International Journal for Parasitology 49 (2019)7. - ISSN 0020-7519 - p. 515 - 522.
Cattle - Detection - Mouse bioassay - PCR - Serology - Toxoplasma gondii

In cattle, antibodies to Toxoplasma gondii infection are frequently detected, but evidence for the presence of T. gondii tissue cysts in cattle is limited. To study the concordance between the presence of anti-T. gondii IgG and viable tissue cysts of T. gondii in cattle, serum, liver and diaphragm samples of 167 veal calves and 235 adult cattle were collected in Italy, the Netherlands, Romania and the United Kingdom. Serum samples were tested for anti-T. gondii IgG by the modified agglutination test and p30 immunoblot. Samples from liver were analyzed by mouse bioassay and PCR after trypsin digestion. In addition, all diaphragms of cattle that had tested T. gondii-positive (either in bioassay, by PCR on trypsin-digested liver or serologically by MAT) and a selection of diaphragms from cattle that had tested negative were analyzed by magnetic capture quantitative PCR (MC-PCR). Overall, 13 animals were considered positive by a direct detection method: seven out of 151 (4.6%) by MC-PCR and six out of 385 (1.6%) by bioassay, indicating the presence of viable parasites. As cattle that tested positive in the bioassay tested negative by MC-PCR and vice-versa, these results demonstrate a lack of concordance between the presence of viable parasites in liver and the detection of T. gondii DNA in diaphragm. In addition, the probability to detect T. gondii parasites or DNA in seropositive and seronegative cattle was comparable, demonstrating that serological testing by MAT or p30 immunoblot does not provide information about the presence of T. gondii parasites or DNA in cattle and therefore is not a reliable indicator of the risk for consumers.

Induction of desiccation tolerance in desiccation sensitive Citrus limon seeds
Marques, Alexandre ; Nijveen, Harm ; Somi, Charles ; Ligterink, Wilco ; Hilhorst, Henk - \ 2019
Journal of Integrative Plant Biology 61 (2019)5. - ISSN 1672-9072 - p. 624 - 638.

Many economically important perennial species bear recalcitrant seeds, including tea, coffee, cocoa, mango, citrus, rubber, oil palm and coconut. Orthodox seeds can be dried almost completely without losing viability, but so-called recalcitrant seeds have a very limited storage life and die upon drying below a higher critical moisture content than orthodox seeds. As a result, the development of long-term storage methods for recalcitrant seeds is compromised. Lowering this critical moisture content would be very valuable since dry seed storage is the safest, most convenient and cheapest method for conserving plant genetic resources. Therefore, we have attempted to induce desiccation tolerance (DT) in the desiccation sensitive seeds of Citrus limon. We show that DT can be induced by paclobutrazol (an inhibitor of gibberellin biosynthesis) and we studied its associated transcriptome to delineate the molecular mechanisms underlying this induction of DT. Paclobutrazol not only interfered with gibberellin related gene expression but also caused extensive changes in expression of genes involved in the biosynthesis and signaling of other hormones. Paclobutrazol induced a transcriptomic switch encompassing suppression of biotic- and induction of abiotic responses. We hypothesize that this is the main driver of the induction of DT by paclobutrazol in C. limon seeds.

Tissue-specific production of limonene in Camelina sativa with the Arabidopsis promoters of genes BANYULS and FRUITFULL
Borghi, Monica ; Xie, De Yu - \ 2016
Planta 243 (2016)2. - ISSN 0032-0935 - p. 549 - 561.
BANYULS - Camelina - FRUITFULL - Limonene - Metabolic engineering - Oilseed crop

Main conclusion: Arabidopsis promoters of genesBANYULSandFRUITFULLare transcribed in Camelina. They triggered the transcription oflimonene synthaseand induced higher limonene production in seeds and fruits thanCaMV 35Spromoter.Camelina sativa (Camelina) is an oilseed crop of relevance for the production of biofuels and the plant has been target of a recent and intense program of genetic manipulation aimed to increase performance, seed yield and to modify the fatty acid composition of the oil. Here, we have explored the performance of two Arabidopsis thaliana (Arabidopsis) promoters in triggering transgene expression in Camelina. The promoters of two genes BANYULS (AtBANpro) and FRUITFULL (AtFULpro), which are expressed in seed coat and valves of Arabidopsis, respectively, have been chosen to induce the expression of limonene synthase (LS) from Citrus limon. In addition, the constitutive CaMV 35S promoter was utilized to overexpress LS in Camelina . The results of experiments revealed that AtBANpro and AtFULpro are actively transcribed in Camelina where they also retain specificity of expression in seeds and valves as previously observed in Arabidopsis. LS induced by AtBANpro and AtFULpro leads to higher limonene production in seeds and fruits than when the CaMV 35S was used to trigger the expression. In conclusion, the results of experiments indicate that AtBANpro and AtFULpro can be successfully utilized to induce the expression of the transgenes of interest in seeds and fruits of Camelina.

Relationship between seroprevalence in the main livestock species and presence of Toxoplasma gondii in meat
Opsteegh, M. ; Maas, Miriam ; Schares, Gereon ; Giessena, Joke van der; Conraths, F. ; Bangoura, Berit ; Blaga, Radu ; Boireau, Pascal ; Vallee, Isabelle ; Djokic, Vitomir ; Roux, Delphine Le; Perret-Duménil, Catherine ; Ducry, Tamara ; Wisselink, H.J. ; Cornelissen, J.B.W.J. ; Villena, Isabelle ; Aubert, Dominique ; Györke, Adriana ; Cozma, Vasile ; Mircean, Viorica ; Pastiu, Anamaria Ioana ; Balea, Anamaria ; Kalmar, Zsuzsa ; Barburas, Diana ; Pozio, Edoardo ; Spano, Furio ; Limon, Georgina ; Georgiev, Milen ; Blake, Damer ; Guitian, Javier ; Dominguez, Javier ; Katzer, Frank ; Burrells, Alison ; Innes, Lee ; Djurkovic-Djakovic, Olgica ; Klunl, Ivana - \ 2016
Toxoplasma gondii in European slaughtered calves and cattle - serology, mouse bioassay and magnetic capture qPCR
Opsteegh, M. ; Aubert, Dominique ; Balea, Anamaria ; Burrells, Alison ; Cherchi, S. ; Cornelissen, J.B.W.J. ; Dam, C. ; Györke, Adriana ; Kalmar, Zsuzsa ; Katzer, Frank ; Limon, Georgina ; Possenti, A. ; Pozio, Edoardo ; Spano, Furio ; Villena, Isabelle ; Wisselink, H.J. ; Giessen, J. van der - \ 2015
Capturing of the monoterpene olefin limonene produced in Saccharomyces cerevisiae
Jongedijk, E.J. ; Cankar, K. ; Ranzijn, J. ; Krol, A.R. van der; Bouwmeester, H.J. ; Beekwilder, M.J. - \ 2015
Yeast 32 (2015)1. - ISSN 0749-503X - p. 159 - 171.
monoterpene biosynthesis - escherichia-coli - synthase - precursor
Monoterpene olefins such as limonene are plant compounds with applications as flavouring and fragrance agents, as solvents and potentially also in polymer and fuel chemistry. We engineered baker's yeast Saccharomyces cerevisiae to express a (-)-limonene synthase from Perilla frutescens and a (+)-limonene synthase from Citrus limon. Both proteins were expressed either with their native plastid targeting signal or in a truncated form in which the plastidial sorting signal was removed. The yeast host strain for expression was AE9 K197G, which expresses a mutant Erg20 enzyme. This enzyme catalyses the formation of geranyl diphosphate, which is the precursor for monoterpenes. Several methods were tested to capture limonene produced by the yeast. Extraction from the culture medium by pentane, or by the addition of CaCl2 followed by solid-phase micro-extraction, did not lead to detectable limonene, indicating that limonene is rapidly lost from the culture medium. Volatile terpenes such as limonene may also be trapped in a dodecane phase added to the medium during fermentation. This method resulted in recovery of 0.028¿mg/l (+)-limonene and 0.060¿mg/l (-)-limonene in strains using the truncated Citrus and Perilla synthases, respectively. Trapping the headspace during culture of the limonene synthase-expressing strains resulted in higher titres, at 0.12¿mg/l (+)-limonene and 0.49¿mg/l (-)-limonene. These results show that the volatile properties of the olefins produced require specific methods for efficient recovery of these molecules from biotechnological production systems. Gene Bank Nos were: KM015220 (Perilla limonene synthase; this study); AF317695 (Perilla limonene synthase; Yuba et al., 1996); AF514287.1 (Citrus limonene synthase; Lucker et al., 2002).
Does functional trait diversity predict aboveground biomass and productivity of tropical forests? Testing three alternative hypotheses
Finegan, B. ; Pena Claros, M. ; Silva de Oliveira, A. ; Ascarrunz, N. ; Bret-Harte, M.S. ; Carreño Rocabado, I.G. ; Casanoves, F. ; Diaz, S. ; Eguiguren Velepucha, P. ; Fernandez, F. ; Licona, J.C. ; Lorenzo, L. ; Salgado Negret, B. ; Vaz, M. ; Poorter, L. - \ 2014
green soup hypothesis - biodiversity - biomass ratio - ecosystem processes - functional traits - commiunity weighted mean - niche complementary
1. Tropical forests are globally important, but it is not clear whether biodiversity enhances carbon storage and sequestration in them. We tested this relationship focusing on components of functional trait biodiversity as predictors. 2. Data are presented for three rain forests in Bolivia, Brazil and Costa Rica. Initial above-ground biomass and biomass increments of survivors, recruits and survivors + recruits (total) were estimated for trees ≥10 cm d.b.h. in 62 and 21 1.0-ha plots, respectively. We determined relationships of biomass increments to initial standing biomass (AGBi), biomass-weighted community mean values (CWM) of eight functional traits and four functional trait variety indices (functional richness, functional evenness, functional diversity and functional dispersion). 3. The forest continuum sampled ranged from ‘slow’ stands dominated by trees with tough tissues and high AGBi, to ‘fast’ stands dominated by trees with soft, nutrient-rich leaves, lighter woods and lower AGBi. 4. We tested whether AGBi and biomass increments were related to the CWM trait values of the dominant species in the system (the biomass ratio hypothesis), to the variety of functional trait values (the niche complementarity hypothesis), or in the case of biomass increments, simply to initial standing biomass (the green soup hypothesis). 5. CWMs were reasonable bivariate predictors of AGBi and biomass increments, with CWM specific leaf area SLA, CWM leaf nitrogen content, CWM force to tear the leaf, CWM maximum adult height Hmax and CWM wood specific gravity the most important. AGBi was also a reasonable predictor of the three measures of biomass increment. In best-fit multiple regression models, CWMHmax was the most important predictor of initial standing biomass AGBi. Only leaf traits were selected in the best models for biomass increment; CWM SLA was the most important predictor, with the expected positive relationship. There were no relationships of functional variety indices to biomass increments, and AGBi was the only predictor for biomass increments from recruits. 6. Synthesis. We found no support for the niche complementarity hypothesis and support for the green soup hypothesis only for biomass increments of recruits. We have strong support for the biomass ratio hypothesis. CWMHmax is a strong driver of ecosystem biomass and carbon storage and CWM SLA, and other CWM leaf traits are especially important for biomass increments and carbon sequestration.
Antibacterial Effects of the Essential Oils of CommonlyConsumed Medicinal Herbs Using an In Vitro Model.
Sokovic, M. ; Glamoclija, J. ; Marin, P.D. ; Brkic, D. ; Griensven, L.J.L.D. van - \ 2010
Molecules 15 (2010)11. - ISSN 1420-3049 - p. 7532 - 7546.
oregano essential oil - salmonella-enteritidis - listeria-monocytogenes - antifungal activities - chemical-composition - escherichia-coli - fungi
The chemical composition and antibacterial activity of essential oils from 10 commonly consumed herbs: Citrus aurantium, C. limon, Lavandula angustifolia, Matricaria chamomilla, Mentha piperita, M. spicata, Ocimum basilicum, Origanum vulgare, Thymus vulgaris and Salvia officinalis have been determined. The antibacterial activity of these oils and their main components; i.e. camphor, carvacrol, 1,8-cineole, linalool, linalyl acetate, limonene, menthol, a-pinene, b-pinene, and thymol were assayed against the human pathogenic bacteria Bacillus subtilis, Enterobacter cloacae, Escherichia coli O157:H7, Micrococcus flavus, Proteus mirabilis, Pseudomonas aeruginosa, Salmonella enteritidis, S. epidermidis, S. typhimurium, and Staphylococcus aureus. The highest and broadest activity was shown by O. vulgare oil. Carvacrol had the highest antibacterial activity among the tested components.
Chemical composition and antibacterial activity of essential oils against human pathogenic bacteria
Sokovic, M. ; Marin, P.D. ; Brkic, D. ; Griensven, L.J.L.D. van - \ 2008
Food 1 (2008)2. - ISSN 1749-7140 - p. 220 - 226.
The chemical composition and antibacterial activity of essential oils from 10 aromatic plants Matricaria chamommilla, Mentha piperita, M. spicata, Lavandula angustifolia, Ocimum basilicum, Thymus vulgaris, Origanum vulgare, Salvia officinalis, Citrus limon and C. aurantium have been determined. Antibacterial activity of these oils and their components; i.e. linalyl acetate, linalool, limonene, pinene, ß-pinene, 1,8-cineole, camphor, carvacrol, thymol and menthol were assayed against a variety of human pathogenic bacteria. The highest and broadest activity was shown by Origanum vulgare oil. Carvacrol possessed the highest antifungal activity among the components tested
Antimicrobial activity of essential oils and their components against the three major pathogens of the cultivated button mushroom
Sokovic, M. ; Griensven, L.J.L.D. van - \ 2006
European Journal of Plant Pathology 116 (2006)3. - ISSN 0929-1873 - p. 211 - 224.
antifungal activities - chemical-composition - aromatic plants - mutagenicity - disease
Essential oils of Matricaria chamommilla, Mentha piperita, M. spicata, Lavandula angusti folia, Ocimum basilicum, Thymus vulgaris, Origanum vulgare, Salvia officinalis, Citrus limon and C. aurantium and their components; linalyl acetate, linalool, limonene, ¿-pinene, ß-pinene, 1,8-cineole, camphor, carvacrol, thymol and menthol were assayed for inhibitory activity against the three major pathogens of the button mushroom, Agaricus bisporus, i.e. the fungi Verticillium fungicola and Trichoderma harzianum and the bacterium Pseudomonas tolaasii. The highest and broadest activity was shown by the Origanum vulgare oil. Carvacrol possessed the highest antifungal activity among the components tested.
Increased and altered fragrance of tobacco plants after metabolic engineering using three monoterpene synthases from lemon
Lücker, J. ; Schwab, W. ; Hautum, B. van; Blaas, J. ; Plas, L.H.W. van der; Bouwmeester, H.J. ; Verhoeven, H.A. - \ 2004
Plant Physiology 134 (2004)1. - ISSN 0032-0889 - p. 510 - 519.
s-linalool synthase - biosynthetic-pathway - volatile compounds - nicotiana-tabacum - gene-expression - floral scents - flowers - transformation - emission - clarkia
Wild-type tobacco (Nicotiana tabacum) plants emit low levels of terpenoids, particularly from the flowers. By genetic modification of tobacco cv Petit Havana SR1 using three different monoterpene synthases from lemon (Citrus limon L. Burm. f.) and the subsequent combination of these three into one plant by crossings, we show that it is possible to increase the amount and alter the composition of the blend of monoterpenoids produced in tobacco plants. The transgenic tobacco plant line with the three introduced monoterpene synthases is emitting -pinene, limonene, and -terpinene and a number of side products of the introduced monoterpene synthases, from its leaves and flowers, in addition to the terpenoids emitted by wild-type plants. The results show that there is a sufficiently high level of substrate accessible for the introduced enzymes
Metabolic engineering of monoterpende biosysnthesis: two step production of (+)-trans-Isopiperitenol by tobacco
Lücker, J. ; Schwab, W. ; Franssen, M.C.R. ; Plas, L.H.W. van der; Bouwmeester, H.J. ; Verhoeven, H.A. - \ 2004
The Plant Journal 39 (2004)1. - ISSN 0960-7412 - p. 135 - 145.
peppermint mentha-piperita - functional expression - limonene enantiomers - linalool synthase - cdna isolation - s-linalool - plants - mint - (-)-limonene - cloning
Monoterpenoid biosynthesis in tobacco was modified by introducing two subsequent enzymatic activities targeted to different cell compartments. A limonene-3-hydroxylase (lim3h) cDNA was isolated from Mentha spicata L. 'Crispa'. This cDNA was used to re-transform a transgenic Nicotiana tabacum'Petit Havana' SR1 (tobacco) line expressing three Citrus limon L. Burm. f. (lemon) monoterpene synthases producing (+)-limonene, gamma-terpinene and (-)-beta-pinene as their main products. The targeting sequences of these synthases indicate that they are probably localized in the plastids, whereas the sequence information of the P450 hydroxylase indicates targeting to the endoplasmatic reticulum. Despite the different location of the enzymes, the introduced P450 hydroxylase proved to be functional in the transgenic plants as it hydroxylated (+)-limonene, resulting in the emission of (+)-trans-isopiperitenol. Some further modifications of the (+)-trans-isopiperitenol were also detected, resulting in the additional emission of 1,3,8-p-menthatriene, 1,5,8-p-menthatriene, p-cymene and isopiperitenone.
Domain swapping of Citrus limon monoterpene synthases: impact on enzymatic activity and product specifity.
Tamer, M.K. el; Lucker, J. ; Bosch, D. ; Verhoeven, H.A. ; Verstappen, F.W.A. ; Schwab, W. ; Tunen, A.J. van; Voragen, A.G.J. ; Maagd, R.A. de; Bouwmeester, H.J. - \ 2003
Archives of Biochemistry and Biophysics 411 (2003). - ISSN 0003-9861 - p. 196 - 203.
site-directed mutagenesis - 5-epi-aristolochene synthase - trichodiene synthase - linalool synthase - germacrene-a - biosynthesis - expression - biology
Monoterpene cyclases are the key enzymes in the monoterpene biosynthetic pathway, as they catalyze the cyclization of the ubiquitous geranyl diphosphate (GDP) to the specific monoterpene skeletons. From Citrus limon, four monoterpene synthase-encoding cDNAs for a P-pinene synthase named Cl(-)betaPINS, a gamma-terpinene synthase named ClgammaTS, and two limonene synthases named Cl(+)LIMS1 and Cl(+)LIMS2 were recently isolated [J. Lucker et al., Eur. J. Biochem. 269 (2002) 3160]. The aim of our work in this study was to identify domains within these monoterpene synthase enzymes determining the product specificity. Domain swapping experiments between Cl(-)betaPINS and ClgammaTS and between Cl(+)LIMS2 and ClyTS were conducted. We found that within the C-terminal domain of these monoterpene synthases, a region comprising 200 amino acids, of which 41 are different between Cl(-)betaPINS and ClgammaTS, determines the specificity for the formation of P-pinene or gamma-terpinene, respectively, while another region localized further downstream is required for a chimeric enzyme to yield products in the same ratio as in the wild-type ClgammaTS. For Cl(+)LIMS2, the two domains together appear to be sufficient for its enzyme specificity, but many chimeras were inactive probably due to the low homology with ClyTS. Molecular modeling was used to further pinpoint the amino acids responsible for the differences in product specificity of ClyTS and Cl(-)betaPINS. (C) 2003 Elsevier Science (USA). All rights reserved.
Monoterpene biosynthesis in lemon (Citrus limon) cDNA isolation and functional analysis of four monoterpene synthases
Lücker, J. ; Tamer, M.K. El; Schwab, W. ; Verstappen, F.W.A. ; Plas, L.H.W. van der; Bouwmeester, H.J. ; Verhoeven, H.A. - \ 2002
European Journal of Biochemistry 269 (2002). - ISSN 0014-2956 - p. 3160 - 3161.
Citrus limon possesses a high content and large variety of monoterpenoids, especially in the glands of the fruit flavedo. The genes responsible for the production of these monoterpenes have never been isolated. By applying a random sequencing approach to a cDNA library from mRNA isolated from the peel of young developing fruit, four monoterpene synthase cDNAs were isolated that appear to be new members of the previously reported tpsb family. Based on sequence homology and phylogenetic analysis, these sequences cluster in two separate groups. All four cDNAs could be functionally expressed in Escherichia coli after removal of their plastid targeting signals. The main products of the enzymes in assays with geranyl diphosphate as substrate were ( )-limonene (two cDNAs) (-)--pinene and -terpinene. All enzymes exhibited a pH optimum around 7; addition of Mn2 as bivalent metal ion cofactor resulted in higher activity than Mg2 , with an optimum concentration of 0.6 mm. Km values ranged from 0.7 to 3.1 ?m. The four enzymes account for the production of 10 out of the 17 monoterpene skeletons commonly observed in lemon peel oil, corresponding to more than 90␘f the main components present
Molecular regulation of plant monoterpene biosynthesis in relation to fragrance
Tamer, M.K. El - \ 2002
Wageningen University. Promotor(en): A.G.J. Voragen; H.J. Bouwmeester; J.P. Roozen. - S.l. : S.n. - ISBN 9789058087522 - 151
citrus limon - citrus sinensis - monoterpenen - welriekendheid - biosynthese - regulatie - moleculaire biologie - plantensamenstelling - genetische modificatie - citrus limon - citrus sinensis - monoterpenes - fragrance - biosynthesis - regulation - genetic engineering - molecular biology - plant composition

Citrus belongs to an important economical group of crops. Fruits have a distinguished and pleasant taste partly due to the presence of terpenes. Furthermore, these terpenes potentially play a role in the resistance against pathogens such as insects and fungi. The aim of this thesis was therefore to study the regulation of terpene biosynthesis in Citrus limon L. Burm. Therefore, monoterpene synthase cDNAs from Citrus limon L. Burm. peel were isolated by a cDNA library-screening approach and to identify specific domains, and possibly amino acids, involved in product specificity within the active site of these enzymes. In addition, we aimed at investigating factors that might positively contribute to the regeneration of transgenic Citrus sinensis (L.) Osbeck cv. Valencia Late plants. Because transforming Citrus was not practical, we aimed at studying the odor effects of transforming a model plant, Nicotiana tabacum , with the isolated Citrus limon monoterpene synthases.

In chapter 2, the isolation, expression and characterization of four new cDNAs belonging to the terpene synthase b sub-family ( tpsb ) family (Bohlmann et al., 1998) and coding for monoterpene synthases in Citrus limon L. Burm . has been described in detail. A random sequencing approach was applied to a cDNA library from mRNA isolated from the peel of a young developing fruit. These monoterpene synthase cDNAs were isolated and all four cDNAs could be functionally expressed in E. coli after removal of their plastid targeting signals. The main products of the enzymes in assays with geranyl diphosphate (GDP) as substrate were (+)-limonene (two cDNAs), (-)-β-pinene andγ-terpinene and these enzymes were named Cl(+)LIMS1, Cl(+)LIMS2, Cl(-)βPINS and ClγTS, respectively.

In chapter 3, the functional differences which were present within the domains of the monoterpene synthases and leading to product specificity in the enzymatic catalysis, have been studied. Domain swapping experiments were conducted as well between Cl(-)βPINS and ClγTS as between Cl(+)LIMS2 and ClγTS . We showed that within the same putative C-terminal structural domain of monoterpene synthases, a region comprising 200 amino acids, of which 41 are different between Cl(-)βPINS and ClγTS, determines the specificity for the formation ofβ-pinene orγ- terpinene, respectively, while another region localized further downstream is required for a chimeric enzyme to yield products with the same ratio as in the wild type ClγTS. For Cl(+)LIMS2, both domains together appear to be sufficient for its enzyme specificity, but probably due to the low homology with ClγTS, many chimeric enzymes were inactive.

In order to find factors that might improve the transformation efficiency of Citrus sinensis (L.) Osbeck cv. Valencia Late, the interactive effects within the regeneration of Citrus sinensis have been studied (Chapter 4). The latter was focused on the influence of the initial germination medium, of the explant type (source) and of the regeneration medium on shoot regeneration. Results show that the germination on MS30 (Murashige & Skoog, 1962) and the regeneration on NNIII (Nitsch & Nitsch, 1969) containing a 20:1 cytokinin: auxin ratio supplied with the riboside form of the benzyl amino purine cytokinin, are essential for an efficient induction of shoot regeneration. In addition, hypocotyl-derived shoot regenerants incubated on NNRtVIII (Nitsch & Nitsch based medium) showed better rooting than epicotyl-derived shoot regenerants and incubation on other media tested.

Finally, with the help of a human panel, the floral fragrance effect of transforming Nicotiana tabacum either together with the Cl(+)LIMS1, Cl(-)βPINS and ClγTS genes, or singly with the Cl(-)βPINS gene has been investigated (Chapter 5). In a triangle experimental design, the panel was able to discriminate significantly between the smell of a transgenic plant and a wild type plant. However, a descriptive panel had difficulties to generate accurate sensory descriptors for smells, and to reach consensus on the precise meaning of chosen attributes in a predetermined small number of panel sessions.

Nevertheless, this thesis illustrates an example where the combination of molecular biology, cell biology and biochemistry, and sensory analysis offers an integrated approach as a first step in trying to unravel the world of plant fragrance emission and perception.

Metabolic engineering of monoterpene biosynthesis in plants
Lücker, J. - \ 2002
Wageningen University. Promotor(en): L.H.W. van der Plas; H.A. Verhoeven; H.J. Bouwmeester. - S.l. : S.n. - ISBN 9789058087171 - 158
nicotiana - petunia - citrus limon - monoterpenen - biosynthese - genetische modificatie - metabolisme - transgene planten - plantenfysiologie - nicotiana - petunia - citrus limon - monoterpenes - biosynthesis - genetic engineering - metabolism - transgenic plants - plant physiology

Monoterpenes are a large group of compounds that belong to the terpenoid family of natural compounds in plants. They are small, volatile, lipophilic substances of which around one thousand different structures have been identified. Monoterpenes are involved in plant-insect, plant-microorganism and plant-plant interactions. Many monoterpenes, such as menthol, carvone, limonene and linalool, are of commercial interest as they are commonly used in foods, beverages, perfumes and cosmetics and in many cleaning products. In flowers they also contribute to the characteristic scent. Monoterpene synthases and subsequent modifying enzymes such as cytochrome P450 hydroxylases, dehydrogenases, reductases and isomerases are responsible for the production of the variety of different carbon skeletons of monoterpenes that are found in nature. In this thesis the use of genetic engineering to introduce or alter the production of monoterpenes by plants was explored.

Initially, as described in Chapter 2, S -linalool synthase from Clarkia breweri was introduced in Petunia plants regulated by a constitutive promoter. Expression was obtained in all tissues analysed, but formation of linalool was restricted to leaves, sepals, corollas, stems and ovaries, and could not be detected in nectaries, roots, pollen and style. Although it was expected that the formation of linalool would result in an alteration of the scent of the plants, no linalool was detected in the headspace. Instead, all the S -linalool produced was efficiently converted by an endogenous glucosyltransferase present in the petunia tissues to the non-volatile S -linalyl-b-D-glucopyranoside. These results showed that genetic engineering of plants for monoterpene biosynthesis is possible, but that it can lead to unexpected conversions of the produced metabolites by endogenous enzyme activities.

In order to obtain new monoterpene synthases for the genetic engineering of plants, a cDNA library was made of the fruit peel of lemon, a plant species producing many different monoterpenes. From this library four different monoterpene synthases were obtained as described in Chapter 3, which together showed to be responsible for more than 90% of the total number of components present in lemon oil. The product specificity of the enzymes could be analysed after heterologous expression in Escherichia coli . Two of the four cDNA-encoded enzymes were producing (+)-limonene, the main component present in lemon. One cDNA-encoded enzyme was mainly producing (-)-b-pinene and the fourth cDNA-encoded enzyme was mainly producingg-terpinene. The latter two enzymes were both producing traces of multiple side products as well. Also other properties of the heterologously expressed enzymes were determined, which are described in Chapter 3.

Three monoterpene synthases responsible for the production of different main products were chosen for the genetic engineering of Nicotiana tabacum 'Petit Havana' SR1, described in Chapter 4. The wild type of this tobacco variety produces one monoterpene, linalool that is only emitted from the flowers. After the transformation with the three monoterpene synthases and subsequent crossings, a plant was obtained that emitted all the three main products of the three introduced monoterpene synthases in addition to the endogenous linalool in the flowers. The levels of limonene,b-pinene andg-terpinene emitted from the leaves and flowers of the plant were higher than the level of the endogenous monoterpene. Also the side products of the monoterpene synthases were detected. The extensive modification of the volatile profile of the tobacco plants that we obtained indicates that there is a sufficient amount of substrate available to the introduced enzymes.

In Chapter 5 the transgenic tobacco plant emitting the products of three monoterpene synthases, was used in a subsequent transformation experiment in order to modify the already introduced pathway. A second step in the pathway was introduced by transformation of the plant material with a limonene-3-hydroxylase isolated from spearmint, which is supposed to be localised in the endoplasmatic reticulum (ER) in the cytosol of the plant cells, while the primarily introduced monoterpene synthases were most likely localised in the plastids in the transgenic plants. The introduction of the cytochrome P450 monoterpene hydroxylase and the resulting formation of the hydroxylated product of (+)-limonene, (+)- trans -isopiperitenol demonstrates that there is intracellular trafficking of limonene from the plastids to the ER in the cytosol. That this trafficking mechanism would be present in plants normally producing these hydroxylated monoterpenes could be expected, but that it is apparently also present in plants not specialised for the production of these compounds is an exciting discovery. Apart from the production and subsequent emission of high further oxidised conversion product isopiperitenone was detected. In addition, an increase in the p -cymene level and the formation of the new products 1,3,8- p -menthatriene and 1,5,8- p -menthatriene were detected. The occurrence of these latter two products and the increase of the p -cymene level could be a consequence of the metabolic engineering of the biosynthetic route into a cell compartment not adapted to the production of these compounds. Endogenous enzymes and pH differences were suggested to be the main cause the formation of these products.

Chapter 6 discusses the various strategies followed for the metabolic engineering of monoterpene biosynthesis in this thesis and by other groups. Functional implications are discussed such as ecological and physiological consequences of the new metabolites for the transgenic plants. The commercial aspects and interesting opportunities for further research are also discussed.

El empresario agricola en el jugoso negocio de las frutas y hortalizas de Mexico
Gonzalez Chavez, H. - \ 1994
Agricultural University. Promotor(en): N.E. Long. - S.l. : Gonzalez Chavez - ISBN 9789054852407 - 361
productiviteit - sociale economie - internationale samenwerking - integratie - productie - planning - economie - export - multinationale corporaties - tuinbouw - mexico - economische samenwerking - productivity - socioeconomics - international cooperation - integration - production - planning - economics - exports - multinational corporations - horticulture - mexico - economic cooperation

Dit werk heeft als doel om het veranderingsproces uit te leggen dat een landbouwstreek heeft ondergaan door de komst van een van oorsprong Noordamerikaanse exportondernemingen van landbouwprodukten. Deze ondernemingen zijn op grote schaal met de verbouw begonnen van groenten en fruit voor de markt in de Verenigde Staten in de wintertijd. Voor de analyse van dit veranderingsproces heb ik gekozen voor een theoretisch en methodisch perspectief dat van de deelnemende actoren uitgaat. Binnen het geheel van actoren, is mijn aandacht vooral uitgegaan naar de ondernemers van Mexicaanse origine. Zij zijn begonnen als producenten van de exportprodukten en door de tijd heen zijn ze gaan deelnemen aan de industriële verwerking. Ze verpakken de produkten, en vermarkten nu in de nationale en internationale markt.

Het studiegebied bevindt zich in het Westen van Mexico, in een vallei die binnen de bergketen ligt van de Sierra Madre Oriental. Deze vallei omvat drie gemeentes in de deelstaat Jalisco: Autlán, Ei Grullo en El Limón.

In dit werk bekijk ik drie problemen van theoretisch karakter. De eerste herziet het probleem van de interventie in de sociale verandering, en in het bijzonder probeert het de vraag te beantwoorden over de rol die de externe "agenten" spelen, in dit geval de multinationale ondernemingen. Mijn positie over deze problematiek is dat het handelen van de transnationale ondernemingen vorm krijgt aan de hand van de weerstanden en de initiatieven van de lokale actoren. Deze actoren zien nieuwe of verschillende mogelijkheden voor hun handelen en voordeel in het licht van de initiatieven en de aanbiedingen van de transnationale ondernemingen als die in hun gebied aankomen.

De lokale ondernemers hebben geen passieve rol ten aanzien van de Amerikaanse ondernemingen; of beter gezegd, ze proberen voordeel te halen uit al hun ervaringen, relaties en middelen die ze hebben. Door middel van het deelnemen aan de produktie van deze gewassen proberen ze betere condities te verkrijgen. Deze betere condities maakt het mogelijk om te groeien en zich los te maken van de technologische, commerciële en financiële afhankelijkheid van de Amerikaanse ondernemingen. Wanneer de lokale ondernemers dat bereiken concurreren ze met de internationale bedrijven voor het verkrijgen van de hoogste economische voordelen.

Het tweede vraagstuk waar deze studie over gaat is het begrijpen van het "globalisatie" of "internationalisatie" proces vanuit het perspectief van de rol die de lokale actoren daarin spelen. In de studie bekritiseer ik de stelling dat er een economische geïntegreerde wereldstructuur als een functioneel geheel bestaat, dat ons leidt naar een grotere economische en culturele homogenisatie. Ten aanzien van deze stelling, benadruk ik de heterogeniteit en de onbepaaldheden in de wereldprocessen, en de noodzaak om specifieke historische processen in elke regio en in elk land te erkennen.

De lokale ondernemers zijn geen actoren die gebonden zijn aan een gebied, een regio of een land. De juridische en administratieve afbakening zijn van historische origine, en hun geldigheid hangt af van de manier waarop elk individu en elke groep er waarde aan geeft en gebruik van maakt. De ondernemers definiëren op een flexibele manier hun grenzen rekening houdend met de behoeften en de belangen van hun onderneming. Op deze manier geven ze continuïteit of openen nieuwe alternatieven ten aanzien van de economische, sociale en culturele relaties. Deze veranderende relaties hebben betrekking op de produktie, de verwerking en de vermarkting in zowel de produktie- als de vermarktingsplaats.

Het derde vraagstuk voor analyse is het gebruik dat de agrarische exportondernemers maken van de natuurlijke bronnen. De centrale vraag is of deze landbouw op de lange termijn het productiviteitsniveau kan handhaven, ten bate van de producenten van de volgende generaties. Mijn aandacht gaat uit naar de produktiewijze van de Amerikaanse en mexicaanse producenten, en de directe gevolgen daarvan op de produktiviteit van de natuurlijke bronnen van het gebied. Het resultaat van deze studie bevestigt de conclusies van andere onderzoekers, dat deze landbouw schade veroorzaakt in de ecosystemen waarin het zich ontwikkelt. Bovendien laat ik zien dat deze manier van het gebruiken van natuurlijke bronnen door de Amerikaanse ondernemingen is ingevoerd en door de lokale producenten is overgenomen. Het wonen in de produktieregio en het eigenaar zijn van het land, hebben tot gevolg dat de lokale ondernemers controlemaatregelen hebben ingevoerd om de verderfelijke effecten van deze produktiewijze tegen te gaan.

De etnografische methodologie heeft het me in deze studie mogelijk gemaakt om de meest relevante informatie in te winnen met als doel me te kunnen verdiepen in de drie hiervoor genoemde vraagstukken.

Deze studie bevat 8 hoofdstukken en conclusies. In het eerste introduceer ik een discussie over de meest relevante bibliografie betreffende studies over landbouwexportbedrijven en behandel ik uitvoerig de in deze samenvatting genoemde vraagstukken. In het tweede hoofdstuk behandel ik gegevens over het studiegebied, Autlán, El Grullo en En Limón, aan de hand van de condities van de Mexicaanse en Amerikaanse exportondernemers die deze landbouwexport zijn begonnen. Het derde en vierde hoofdstuk analyseert de expansie de lokale landbouwexportbedrijven. De hoofdstukken vijf tot en met acht hebben met elkaar gemeen dat het case-studies zijn over de ondernemersloopbaan van verschillende lokale producenten. Deze cases laten ons de heterogeniteit zien in de ontwikkelingsprocessen en de vele verschillende antwoorden van de deelnemende actoren. Elk hoofdstuk is een eenheid op zich dat rekening geeft van het opkomen en de consolidatie van de individuele en collectieve landbouwexportondernemingen.

Unos aspectos historticos de desarrollo de la irrigacion en la region Autlan-El Grullo-El Limon, desde 1900, primera parte: 1900-1965, first draft.
Zaag, P. van der - \ 1988
Unknown Publisher
Los problemas juridicos agrarios de la provincia de Limón
Bolaños, C. ; Ulate, C.E. - \ 1987
Turrialba [etc.] : CATIE [etc.] (Working document / CATIE - UAW - MAG 4) - 46
landbouw - landbouwproductie - recht - wetgeving - plattelandsontwikkeling - costa rica - agriculture - agricultural production - law - legislation - rural development
Structural aspects of female sterility in Citrus limon
Wilms, H.J. ; Went, J.L. van; Cresti, M. ; Ciampolini, F. - \ 1983
Acta botanica neerlandica 32 (1983). - ISSN 0044-5983 - p. 87 - 96.
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