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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    Comparative Metabolomics and Molecular Phylogenetics of Melon (Cucumis melo, Cucurbitaceae) Biodiversity
    Moing, Annick ; Allwood, J.W. ; Aharoni, Asaph ; Baker, John ; Beale, M.H. ; Ben-Dor, Shifra ; Biais, B. ; Brigante, Federico ; Burger, Yosef ; Deborde, C. ; Erban, A. ; Doron-Faigenboim, Adi ; Gur, Amit ; Goodacre, R. ; Hansen, T. ; Jacob, Daniel ; Katzir, Nurit ; Kopka, Joachim ; Lewinsohn, Efraim ; Maucourt, Mickael ; Meir, Sagit ; Miller, Sonia ; Mumm, R. ; Oren, Elad ; Paris, Harry S. ; Rogachev, Ilana ; Rollin, Dominique ; Saar, Uzi ; Schjoerring, Jan K. ; Tadmor, Y. ; Tzuri, Galil ; Vos, C.H. de; Ward, J. ; Yeselson, Elena ; Hall, R.D. ; Schaffer, A. - \ 2020
    Metabolites 10 (2020)3. - ISSN 2218-1989 - 26 p.
    The broad variability of Cucumis melo (melon, Cucurbitaceae) presents a challenge to conventional classification and organization within the species. To shed further light on the infraspecific relationships within C. melo, we compared genotypic and metabolomic similarities among 44 accessions representative of most of the cultivar-groups. Genotyping-by-sequencing (GBS) provided
    over 20,000 single-nucleotide polymorphisms (SNPs). Metabolomics data of the mature fruit flesh and rind provided over 80,000 metabolomic and elemental features via an orchestra of six complementary metabolomic platforms. These technologies probed polar, semi-polar, and non-polar metabolite
    fractions as well as a set of mineral elements and included both flavor- and taste-relevant volatile and non-volatile metabolites. Together these results enabled an estimate of “metabolomic/elemental distance” and its correlation with the genetic GBS distance of melon accessions. This study indicates
    that extensive and non-targeted metabolomics/elemental characterization produced classifications that strongly, but not completely, reflect the current and extensive genetic classification. Certain melon Groups, such as Inodorous, clustered in parallel with the genetic classifications while other genome
    to metabolome/element associations proved less clear. We suggest that the combined genomic, metabolic, and element data reflect the extensive sexual compatibility among melon accessions and the breeding history that has, for example, targeted metabolic quality traits, such as taste and flavor.
    Metabolomics should be deployed in the identification and characterization of gene-edited crops
    Fraser, Paul D. ; Aharoni, Asaph ; Hall, Robert D. ; Huang, Sanwen ; Giovannoni, James J. ; Sonnewald, Uwe ; Fernie, Alisdair R. - \ 2020
    The Plant Journal 102 (2020)5. - ISSN 0960-7412 - p. 897 - 902.
    crop regulation - food system - genome-editing - metabolomics - substantial equivalence

    Gene-editing techniques are currently revolutionizing biology, allowing far greater precision than previous mutagenic and transgenic approaches. They are becoming applicable to a wide range of plant species and biological processes. Gene editing can rapidly improve a range of crop traits, including disease resistance, abiotic stress tolerance, yield, nutritional quality and additional consumer traits. Unlike transgenic approaches, however, it is not facile to forensically detect gene-editing events at the molecular level, as no foreign DNA exists in the elite line. These limitations in molecular detection approaches are likely to focus more attention on the products generated from the technology than on the process in itself. Rapid advances in sequencing and genome assembly increasingly facilitate genome sequencing as a means of characterizing new varieties generated by gene-editing techniques. Nevertheless, subtle edits such as single base changes or small deletions may be difficult to distinguish from normal variation within a genotype. Given these emerging scenarios, downstream ‘omics’ technologies reflective of edited affects, such as metabolomics, need to be used in a more prominent manner to fully assess compositional changes in novel foodstuffs. To achieve this goal, metabolomics or ‘non-targeted metabolite analysis’ needs to make significant advances to deliver greater representation across the metabolome. With the emergence of new edited crop varieties, we advocate: (i) concerted efforts in the advancement of ‘omics’ technologies, such as metabolomics, and (ii) an effort to redress the use of the technology in the regulatory assessment for metabolically engineered biotech crops.

    A MYB Triad Controls Primary and Phenylpropanoid Metabolites for Pollen Coat Patterning
    Battat, Maor ; Eitan, Asa ; Rogachev, Ilana ; Hanhineva, Kati ; Fernie, Alisdair ; Tohge, Takayuki ; Beekwilder, Jules ; Aharoni, Asaph - \ 2019
    Plant Physiology 180 (2019)1. - ISSN 0032-0889 - p. 87 - 108.

    The pollen wall is a complex, durable structure essential for plant reproduction. A substantial portion of phenylpropanoids (e.g. flavonols) produced by pollen grain tapetal cells are deposited in the pollen wall. Transcriptional regulation of pollen wall formation has been studied extensively, and a specific regulatory mechanism for Arabidopsis (Arabidopsis thaliana) pollen flavonol biosynthesis has been postulated. Here, metabolome and transcriptome analyses of anthers from mutant and overexpression genotypes revealed that Arabidopsis MYB99, a putative ortholog of the petunia (Petunia hybrida) floral scent regulator ODORANT1 (ODO1), controls the exclusive production of tapetum diglycosylated flavonols and hydroxycinnamic acid amides. We discovered that MYB99 acts in a regulatory triad with MYB21 and MYB24, orthologs of emission of benzenoids I and II, which together with ODO1 coregulate petunia scent biosynthesis genes. Furthermore, promoter-activation assays showed that MYB99 directs precursor supply from the Calvin cycle and oxidative pentose-phosphate pathway in primary metabolism to phenylpropanoid biosynthesis by controlling TRANSKETOLASE2 expression. We provide a model depicting the relationship between the Arabidopsis MYB triad and structural genes from primary and phenylpropanoid metabolism and compare this mechanism with petunia scent control. The discovery of orthologous protein triads producing related secondary metabolites suggests that analogous regulatory modules exist in other plants and act to regulate various branches of the intricate phenylpropanoid pathway.

    The WEIZMASS spectral library for high-confidence metabolite identification
    Shahaf, Nir ; Rogachev, Ilana ; Heinig, Uwe ; Meir, Sagit ; Malitsky, Sergey ; Battat, Maor ; Wyner, Hilary ; Zheng, Shuning ; Wehrens, Ron ; Aharoni, Asaph - \ 2016
    Nature Communications 7 (2016). - ISSN 2041-1723

    Annotation of metabolites is an essential, yet problematic, aspect of mass spectrometry (MS)-based metabolomics assays. The current repertoire of definitive annotations of metabolite spectra in public MS databases is limited and suffers from lack of chemical and taxonomic diversity. Furthermore, the heterogeneity of the data prevents the development of universally applicable metabolite annotation tools. Here we present a combined experimental and computational platform to advance this key issue in metabolomics. WEIZMASS is a unique reference metabolite spectral library developed from high-resolution MS data acquired from a structurally diverse set of 3,540 plant metabolites. We also present MatchWeiz, a multi-module strategy using a probabilistic approach to match library and experimental data. This strategy allows efficient and high-confidence identification of dozens of metabolites in model and exotic plants, including metabolites not previously reported in plants or found in few plant species to date.

    An O-methyltransferase modifies accumulation of methylated anthocyanins in seedlings of tomato
    Gomez Roldan, M.V. ; Outchkourov, N.S. ; Houwelingen, A.M.M.L. van; Lammers, M. ; Romero Fuente, I. ; Ziklo, N. ; Aharoni, A. ; Hall, R.D. ; Beekwilder, M.J. - \ 2014
    The Plant Journal 80 (2014)4. - ISSN 0960-7412 - p. 695 - 708.
    plant transformation - transcription factor - petunia-hybrida - fruit - biosynthesis - expression - protein - system - metabolome - infection
    Anthocyanins contribute to the appearance of fruit by conferring to them a red, blue or purple colour. In a food context, they have also been suggested to promote consumer health. In purple tomato tissues, such as hypocotyls, stems and purple fruits, various anthocyanins accumulate. These molecules have characteristic patterns of modification, including hydroxylations, methylations, glycosylations and acylations. The genetic basis for many of these modifications has not been fully elucidated, and nor has their role in the functioning of anthocyanins. In this paper, AnthOMT, an O-methyltransferase (OMT) mediating the methylation of anthocyanins, has been identified and functionally characterized using a combined metabolomics and transcriptomics approach. Gene candidates were selected from the draft tomato genome, and their expression was subsequently monitored in a tomato seedling system comprising three tissues and involving several time points. In addition, we also followed gene expression in wild-type red and purple transgenic tomato fruits expressing Rosea1 and Delila transcription factors. Of the 57 candidates identified, only a single OMT gene showed patterns strongly correlating with both accumulation of anthocyanins and expression of anthocyanin biosynthesis genes. This candidate (AnthOMT) was compared to a closely related caffeoyl CoA OMT by recombinant expression in Escherichia coli, and then tested for substrate specificity. AnthOMT showed a strong affinity for glycosylated anthocyanins, while other flavonoid glycosides and aglycones were much less preferred. Gene silencing experiments with AnthOMT resulted in reduced levels of the predominant methylated anthocyanins. This confirms the role of this enzyme in the diversification of tomato anthocyanins.
    Biosynthesis of Antinutritional Alkaloids in Solanaceous Crops Is Mediated by Clustered Genes
    Itkin, M. ; Heinig, U. ; Tzfadia, O. ; Bhide, A.J. ; Shinde, B. ; Cardenas, P.D. ; Bocobza, S.E. ; Unger, T. ; Malitsky, S. ; Finkers, H.J. ; Tikunov, Y.M. ; Bovy, A.G. ; Chikate, Y. ; Singh, P. ; Rogachev, I. ; Beekwilder, J. ; Giri, A.P. ; Aharoni, A. - \ 2013
    Science 341 (2013)6142. - ISSN 0036-8075 - p. 175 - 179.
    glycoalkaloids - potato - plant - metabolites - pathways - saponins - tomato
    Steroidal glycoalkaloids (SGAs) such as a-solanine found in solanaceous food plants—as, for example, potato—are antinutritional factors for humans. Comparative coexpression analysis between tomato and potato coupled with chemical profiling revealed an array of 10 genes that partake in SGA biosynthesis. We discovered that six of them exist as a cluster on chromosome 7, whereas an additional two are adjacent in a duplicated genomic region on chromosome 12. Following systematic functional analysis, we suggest a revised SGA biosynthetic pathway starting from cholesterol up to the tetrasaccharide moiety linked to the tomato SGA aglycone. Silencing GLYCOALKALOID METABOLISM 4 prevented accumulation of SGAs in potato tubers and tomato fruit. This may provide a means for removal of unsafe, antinutritional substances present in these widely used food crops.
    GLYCOALKALOID METABOLISM1 Is Required for Steroidal Alkaloid Glycosylation and Prevention of Phytotoxicity
    Itkin, M. ; Rogachev, I. ; Alkan, N. ; Rosenberg, T. ; Malitsky, S. ; Masini, L. ; Meir, S. ; Lijima, Y. ; Aoki, K. ; Vos, R.C.H. de; Prusky, D. ; Beekwilder, M.J. ; Aharoni, A. - \ 2011
    The Plant Cell 23 (2011)12. - ISSN 1040-4651 - p. 4507 - 4525.
    campestris pv. vesicatoria - induced membrane disruption - alpha-tomatine - saponin biosynthesis - lycopersicon-esculentum - solanum-tuberosum - mass-spectrometry - gene-expression - plant - fruit
    Steroidal alkaloids (SAs) are triterpene-derived specialized metabolites found in members of the Solanaceae family that provide plants with a chemical barrier against a broad range of pathogens. Their biosynthesis involves the action of glycosyltransferases to form steroidal glycoalkaloids (SGAs). To elucidate the metabolism of SGAs in the Solanaceae family, we examined the tomato (Solanum lycopersicum) GLYCOALKALOID METABOLISM1 (GAME1) gene. Our findings imply that GAME1 is a galactosyltransferase, largely performing glycosylation of the aglycone tomatidine, resulting in SGA production in green tissues. Downregulation of GAME1 resulted in an almost 50% reduction in a-tomatine levels (the major SGA in tomato) and a large increase in its precursors (i.e., tomatidenol and tomatidine). Surprisingly, GAME1-silenced plants displayed growth retardation and severe morphological phenotypes that we suggest occur as a result of altered membrane sterol levels caused by the accumulation of the aglycone tomatidine. Together, these findings highlight the role of GAME1 in the glycosylation of SAs and in reducing the toxicity of SA metabolites to the plant cell.
    Isolation and characterisation of a strawberry fruit-specific promotor
    Schaart, J.G. ; Salentijn, E.M.J. ; Pelgrom, K.T.B. ; Aharoni, A. ; Krens, F.A. - \ 2011
    Genes, Genomes and Genomics 5 (2011)Special Issue 1. - ISSN 1749-0383 - p. 108 - 114.
    In order to achieve specific expression of transgenes in strawberry fruits, the availability of tissue- (receptacle) specific promoter sequences is desired. For this reason, 5'-upstream sequences of the strawberry expansin gene FaExp2, which is expressed in a fruit-specific manner, have been isolated. To characterise the promoter activity of the isolated sequences, fragments of 0.7 kb (0.7pFaExp2)and 1.6 kb (1.6pFaExp2) have been fused to the ß-glucuronidase reporter gene (gus). In transgenic strawberry plants transformed with either 0.7pFaExp2-gus or1.6pFaExp2-gus, a fruit-specific expression pattern was observed for both promoter constructs. However, quantitative RT-PCR revealed that gus expression levels driven by the 1.6pFaExp2 promoter fragment were much more higher. In addition to the expression in fruits, both promoter fragments also seemed to direct gene expression in the achenes and to some extent in epidermal and subepidermal tissues of petioles and stems of flowers and fruits. It is concluded that both promoter sequences are suitable for directing transgene expression in strawberry fruits in a specific way
    Extensive metabolic cross-talk in melon fruit revealed by spatial and developmental combinatorial metabolomics
    Moing, A. ; Aharoni, A. ; Biais, B. ; Rogachev, I. ; Meir, S. ; Brodsky, L. ; Allwood, J.W. ; Erban, A. ; Dunn, W.B. ; Kay, S. ; Koning, S. ; Vos, C.H. de; Jonker, H.H. ; Mumm, R. ; Deborde, C. ; Maucourt, M. ; Bernillon, S. ; Gibon, Y. ; Hansen, T.H. ; Husted, S. ; Goodacre, R. ; Kopka, J. ; Schjoerring, J.K. ; Rolin, D. ; Hall, R.D. - \ 2011
    New Phytologist 190 (2011)3. - ISSN 0028-646X - p. 683 - 696.
    mass-spectrometry data - cucumis-melo - gas-chromatography - network analysis - aroma volatiles - gene-expression - tomato - plants - l. - identification
    Celiac disease (CD) is a chronic inflammatory disease affecting the small intestinal mucosa. The causative agents have been identified as gluten proteins from wheat, barley and rye, and the only available treatment for CD patients is a lifelong gluten-free diet. Non-gluten containing cereals would be a valuable contribution to the gluten-free diet. In this respect, oats are a good choice. However, commercial lots of oat flakes and flour frequently are contaminated with wheat, barley and rye, and two studies have reported that some peptides derived from the gluten-like avenin storage proteins of oat can trigger an immune response in some CD patients. In the present study we have initiated the investigation whether all oat varieties contain similar amounts of potentially harmful sequences by biochemical and immunological methods. We confirm that commercial oat preparations are contaminated with other cereals that contain gluten or gluten-like proteins. Moreover, our results demonstrate that contamination-free oat varieties differ in their capacity to stimulate an avenin-sensitive gamma-gliadin specific T cell line derived from a patient with CD, indicative for differences in the two known avenin epitopes among oat varieties, implying that selection and breeding of completely safe oat varieties for all CD patients may be a realistic possibility.
    Fruit-Surface Flavonoid Accumulation in Tomato Is Controlled by a SlMYB12-Regulated Transcriptional Network
    Adato, A. ; Mandel, T. ; Mintz-Orion, S. ; Venger, I. ; Levy, D. ; Yativ, M. ; Dominguez, E. ; Wang, Z. ; Vos, C.H. de; Jetter, R. ; Schreiber, L. ; Heredia, A. ; Rogachev, I. ; Aharoni, A. - \ 2009
    Plos Genetics 5 (2009)12. - ISSN 1553-7404 - 23 p.
    affects vegetative development - phenylpropanoid biosynthesis - liquid-chromatography - arabidopsis-thaliana - gene - expression - evolution - identification - metabolism - regulator
    The cuticle covering plants' aerial surfaces is a unique structure that plays a key role in organ development and protection against diverse stress conditions. A detailed analysis of the tomato colorless-peel y mutant was carried out in the framework of studying the outer surface of reproductive organs. The y mutant peel lacks the yellow flavonoid pigment naringenin chalcone, which has been suggested to influence the characteristics and function of the cuticular layer. Large-scale metabolic and transcript profiling revealed broad effects on both primary and secondary metabolism, related mostly to the biosynthesis of phenylpropanoids, particularly flavonoids. These were not restricted to the fruit or to a specific stage of its development and indicated that the y mutant phenotype is due to a mutation in a regulatory gene. Indeed, expression analyses specified three R2R3-MYB–type transcription factors that were significantly down-regulated in the y mutant fruit peel. One of these, SlMYB12, was mapped to the genomic region on tomato chromosome 1 previously shown to harbor the y mutation. Identification of an additional mutant allele that co-segregates with the colorless-peel trait, specific down-regulation of SlMYB12 and rescue of the y phenotype by overexpression of SlMYB12 on the mutant background, confirmed that a lesion in this regulator underlies the y phenotype. Hence, this work provides novel insight to the study of fleshy fruit cuticular structure and paves the way for the elucidation of the regulatory network that controls flavonoid accumulation in tomato fruit cuticle
    Redirection of flavonoid biosynthesis through the down-regulation of an anthocyanidin glucosyltransferase in ripening strawberry fruit
    Griesser, M. ; Hoffmann, T. ; Bellido, M.L. ; Rosati, C. ; Fink, B. ; Kurtzer, R. ; Aharoni, A. ; Munoz-Blanco, J. ; Schwab, W. - \ 2008
    Plant Physiology 146 (2008)4. - ISSN 0032-0889 - p. 1528 - 1539.
    fragaria x ananassa - phenylalanine ammonia-lyase - udp-glucose - gene-expression - molecular characterization - arabidopsis-thaliana - oxidative stress - petunia-hybrida - pathway genes - cinnamic acid
    Strawberry (Fragaria x ananassa) fruit contains several anthocyanins that give the ripe fruits their attractive red color. The enzyme that catalyzes the formation of the first stable intermediate in the anthocyanin pathway is anthocyanidin-3-O-glucosyltransferase. A putative glycosyltransferase sequence (FaGT1) was cloned from a strawberry fruit cDNA library and the recombinant FaGT1 transferred UDP-glucose to anthocyanidins and, to a lesser extent, flavonols, generating the respective 3-O-glucosides. Quantitative polymerase chain reaction revealed that transcripts of FaGT1 were almost undetectable in green fruits, but gene expression increased dramatically in both turning and ripe red fruit, corresponding closely to the accumulation of anthocyanins during fruit ripening. The expression of FaGT1 is fruit associated and negatively regulated by auxin. To elucidate the in planta function of FaGT1, Agrobacterium tumefaciens cells harboring an intron-hairpin construct of a partial FaGT1 sequence were injected into midsized ripening fruits. In about one-third of the injected fruits, this led to significant down-regulation of FaGT1 transcript levels that corresponded to reduced concentrations of anthocyanin pigments in ripe strawberry fruits. In contrast, significant levels of epiafzelechin-formed by anthocyanidin reductase (ANR) from pelargonidin-were identified in FaGT1-silenced fruits, indicating competition of FaGT1 and FaANR for the common anthocyanidin substrate. Thus, FaGT1 represents an important branching-point enzyme because it is channeling the flavonoid pathway to anthocyanins. These results demonstrate a method to redirect the anthocyanin biosynthesis into flavan-3-ol production to increase the levels of bioactive natural products or modify pigments in plant tissues.
    A transgenic plant having enhanced drought tolerance
    Aharoni, A. ; Dixit, S.A. ; Trijatmiko, K.R. ; Hiemstra, J.A. ; Pereira, A.B. - \ 2007
    Octrooinummer: WO2007030001, gepubliceerd: 2007-03-15.
    The present invention relates to the field of transgenic plants with novel phenotypes, especially plants with enhanced drought and pathogen resistance. Provided are transgenic crop plants comprising integrated in their genome a chimeric gene, characterized by said chimeric gene comprising a transcription regulatory sequence active in plant cells operably linked to a nucleic acid sequence encoding a protein having the sequence of SEQ ID NO: 3 or a protein at least 70 % identical to SEQ ID NO: 3, or an ortholog protein or a functional fragment thereof. In addition to enhanced drought tolerance the transgenic plants may show enhanced disease resistance and enhanced root structure.
    Metabolic engineering of terpene biosynthesis in Arabidopsis and consequences for plant-environment communication
    Bouwmeester, H.J. ; Kappers, I.F. ; Aharoni, A. ; Ruyter-Spira, C.P. ; Sun, Z. ; Charnikhova, T. ; Cardoso Antunes, C.G. ; Dicke, M. - \ 2007
    Metabolic engineering of terpene biosynthesis and consequences for plant-insect interaction
    Bouwmeester, H.J. ; Kappers, I.F. ; Aharoni, A. ; Dicke, M. - \ 2007
    Improvement of water use efficiency in rice by expression of HARDY, an Arabidopsis drought and salt tolerance gene
    Karaba, A. ; Dixit, S.A. ; Greco, Raffaella ; Aharoni, A. ; Trijatmiko, K.R. ; Marsch-Martinez, N. ; Krishnan, A. ; Nataraja, K.N. ; Udayakumar, M. ; Pereira, A.B. - \ 2007
    Proceedings of the National Academy of Sciences of the United States of America 104 (2007)39. - ISSN 0027-8424 - p. 15270 - 15275.
    freezing tolerance - resistance - transformation - mechanisms - responses - plants - yield
    Freshwater is a limited and dwindling global resource; therefore, efficient water use is required for food crops that have high water demands, such as rice, or for the production of sustainable energy biomass. We show here that expression of the Arabidopsis HARDY (HRD) gene in rice improves water use efficiency, the ratio of biomass produced to the water used, by enhancing photosynthetic assimilation and reducing transpiration. These drought-tolerant, low-water-consuming rice plants exhibit increased shoot biomass under well irrigated conditions and an adaptive increase in root biomass under drought stress. The HRD gene, an AP2/ERF-like transcription factor, identified by a gain-of-function Arabidopsis mutant hrd-D having roots with enhanced strength, branching, and cortical cells, exhibits drought resistance and salt tolerance, accompanied by an enhancement in the expression of abiotic stress associated genes. HRD overexpression in Arabidopsis produces thicker leaves with more chloroplast-bearing mesophyll cells, and in rice, there is an increase in leaf biomass and bundle sheath cells that probably contributes to the enhanced photosynthesis assimilation and efficiency. The results exemplify application of a gene identified from the model plant Arabidopsis for the improvement of water use efficiency coincident with drought resistance in the crop plant rice.
    Metabolic engineering of terpenoid biosynthesis in plants
    Lücker, J. ; Bouwmeester, H.J. ; Aharoni, A. - \ 2007
    In: Applications of plant metabolic engineering / Verpoorte, R., Alferman, W., Johnson, T.S., Berlin : Springer Verlag - ISBN 9781402060304 - p. 211 - 218.
    Metabolic engineering of terpenoid biosynthesis in plants
    Aharoni, A. ; Jongsma, M.A. ; Kim, T.Y. ; Ri, M.B. ; Giri, A.P. ; Verstappen, F.W.A. ; Schwab, W. ; Bouwmeester, H.J. - \ 2006
    Phytochemistry Reviews 5 (2006)1. - ISSN 1568-7767 - p. 49 - 58.
    Metabolic engineering of terpenoids in plants is a fascinating research topic from two main perspectives. On the one hand, the various biological activities of these compounds make their engineering a new tool for improving a considerable number of traits in crops. These include for example enhanced disease resistance, weed control by producing allelopathic compounds, better pest management, production of medicinal compounds, increased value of ornamentals and fruit and improved pollination. On the other hand, the same plants altered in the profile of terpenoids and their precursor pools make a most important contribution to fundamental studies on terpenoid biosynthesis and its regulation. In this review we describe our recent results with terpenoid engineering, focusing on two terpenoid classes the monoterpenoids and sesquiterpenoids. The emerging picture is that engineering of these compounds and their derivatives in plant cells is feasible, although with some requirements and limitations. For example, in terpenoid engineering experiments crucial factors are the subcellular localisation of both the precursor pool and the introduced enzymes, the activity of endogenous plant enzymes which modify the introduced terpenoid skeleton, the costs of engineering in terms of effects on other pathways sharing the same precursor pool and the phytotoxicity of the introduced terpenoids. Finally, we will show that transgenic plants altered in their terpenoid profile exert novel biological activities on their environment, for example influencing insect behaviour
    Cinnamate metabolism in ripening fruit. Characterization of a UDP-glucose: Cinnamate glucosyltransferase from strawberry
    Lunkenbein, S. ; Bellido, M.L. ; Aharoni, A. ; Salentijn, E.M.J. ; Kaldenhoff, R. ; Coiner, H. ; Munoz-Blanco, J. ; Schwab, W. - \ 2006
    Plant Physiology 140 (2006)3. - ISSN 0032-0889 - p. 1047 - 1058.
    fragaria x ananassa - heterologous expression - arabidopsis-thaliana - pectate lyase - flavonoid 3-o-glucosyltransferase - cultivated strawberries - substrate-specificity - o-glucosyltransferase - molecular-cloning - dna microarrays
    Strawberry (Fragaria x ananassa) fruit accumulate (hydroxy)cinnamoyl glucose (Glc) esters, which may serve as the biogenetic precursors of diverse secondary metabolites, such as the flavor constituents methyl cinnamate and ethyl cinnamate. Here, we report on the isolation of a cDNA encoding a UDP-Glc:cinnamate glucosyltransferase (Fragaria x ananassa glucosyltransferase 2 [FaGT2]) from ripe strawberry cv Elsanta that catalyzes the formation of 1-O-acyl-Glc esters of cinnamic acid, benzoic acid, and their derivatives in vitro. Quantitative real-time PCR analysis indicated that FaGT2 transcripts accumulate to high levels during strawberry fruit ripening and to lower levels in flowers. The levels in fruits positively correlated with the in planta concentration of cinnamoyl, p-coumaroyl, and caffeoyl Glc. In the leaf, high amounts of Glc esters were detected, but FaGT2 mRNA was not observed. The expression of FaGT2 is negatively regulated by auxin, induced by oxidative stress, and by hydroxycinnamic acids. Although FaGT2 glucosylates a number of aromatic acids in vitro, quantitative analysis in transgenic lines containing an antisense construct of FaGT2 under the control of the constitutive 35S cauliflower mosaic virus promoter demonstrated that the enzyme is only involved in the formation of cinnamoyl Glc and p-coumaroyl Glc during ripening.
    Fruit flavor formation in wild and cultivated strawberry
    Aharoni, A. ; Verstappen, F.W.A. ; Bouwmeester, H.J. ; Beekwilder, M.J. - \ 2005
    Acta Horticulturae 682 (2005). - ISSN 0567-7572 - p. 233 - 236.
    In recent years we have used various genomics tools to investigate ripening in strawberry, in particular the process of fruit flavor biogenesis. The combination of biochemical analysis, generation of a strawberry Expressed Sequence Tags (EST) collection and gene expression analysis using cDNA microarrays resulted in the identification of several genes playing a key role in the formation of volatile flavors during strawberry fruit ripening. Genes associated with the biosynthesis of lipid-derived flavors, such as esters, and those involved in the formation of mono- and sesquiterpenes have been isolated. In this report we summarize the main results obtained by functional characterization of the genes identified. Moreover, differences in volatile profiles between the wild, diploid strawberry and the cultivated, octaploid strawberry allowed us to obtain insight into the molecular processes which resulted in the formation of a certain flavor component and the loss of another
    Volatile science? Metabolic engineering of terpenoids in plants
    Aharoni, A. ; Jongsma, M.A. ; Bouwmeester, H.J. - \ 2005
    Trends in Plant Science 10 (2005)12. - ISSN 1360-1385 - p. 594 - 602.
    transgenic arabidopsis plants - linalool synthase gene - isoprenoid biosynthesis - essential oil - monoterpene biosynthesis - diphosphate synthase - s-linalool - functional expression - menthofuran synthase - plastidial pathways
    Terpenoids are important for plant survival and also possess biological properties that are beneficial to humans. Here, we describe the state of the art in terpenoid metabolic engineering, showing that significant progress has been made over the past few years. Subcellular targeting of enzymes has demonstrated that terpenoid precursors in subcellular compartments are not as strictly separated as previously thought and that multistep pathway engineering is feasible, even across cell compartments. These engineered plants show that insect behavior is influenced by terpenoids. In the future, we expect rapid progress in the engineering of terpenoid production in plants. In addition to commercial applications, such transgenic plants should increase our understanding of the biological relevance of these volatile secondary metabolites
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