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At least 595 records · Page 33Linked to original sources
PubMed2002

Genetic transformation of Vitis vinifera via organogenesis.

BACKGROUND: Efficient transformation and regeneration methods are a priority for successful application of genetic engineering to vegetative propagated plants such as grape. The current methods for the production of transgenic grape plants are based on Agrobacterium-mediated transformation followed by regeneration from embryogenic callus. However, grape embryogenic calli are laborious to establish and the phenotype of the regenerated plants can be altered. RESULTS: Transgenic grape plants (V. vinifera, table-grape cultivars Silcora and Thompson Seedless) were produced using a method based on regeneration via organogenesis. In vitro proliferating shoots were cultured in the presence of increasing concentrations of N6-benzyl adenine. The apical dome of the shoot was removed at each transplantation which, after three months, produced meristematic bulk tissue characterized by a strong capacity to differentiate adventitious shoots. Slices prepared from the meristematic bulk were used for Agrobacterium-mediated transformation of grape plants with the gene DefH9-iaaM. After rooting on kanamycin containing media and greenhouse acclimatization, transgenic plants were transferred to the field. At the end of the first year of field cultivation, DefH9-iaaM grape plants were phenotypically homogeneous and did not show any morphological alterations in vegetative growth. The expression of DefH9-iaaM gene was detected in transgenic flower buds of both cultivars. CONCLUSIONS: The phenotypic homogeneity of the regenerated plants highlights the validity of this method for both propagation and genetic transformation of table grape cultivars. Expression of the DefH9-iaaM gene takes place in young flower buds of transgenic plants from both grape cultivars.

Food Industry↗
PubMed2000

Nonhost resistance and nonspecific plant defenses.

In the past year, most of the advances in our understanding of nonhost resistance to plant pathogens have been incremental. Highlights include the discovery of a general bacterial elicitor of plant defenses, the description of more similarities between the hypersensitive response and animal programmed cell death, and a growing appreciation of the cell wall as the site of initiation and expression of nonhost resistance towards fungi.

Apoptosis↗
PubMed1998

GENES AND ENZYMES OF CAROTENOID BIOSYNTHESIS IN PLANTS.

Carotenoids are integral and essential components of the photosynthetic membranes in all plants. Within the past few years, genes encoding nearly all of the enzymes required for the biosynthesis of these indispensable pigments have been identified. This review focuses on recent findings as to the structure and function of these genes and the enzymes they encode. Three topics of current interest are also discussed: the source of isopentenyl pyrophosphate for carotenoid biosynthesis, the progress and possibilities of metabolic engineering of plants to alter carotenoid content and composition, and the compartmentation and association of the carotenogenic enzymes. A speculative schematic model of carotenogenic enzyme complexes is presented to help frame and provoke insightful questions leading to future experimentation.

Journal Article↗
PubMed1995

Genetic elements of plant viruses as tools for genetic engineering.

Viruses have developed successful strategies for propagation at the expense of their host cells. Efficient gene expression, genome multiplication, and invasion of the host are enabled by virus-encoded genetic elements, many of which are well characterized. Sequences derived from plant DNA and RNA viruses can be used to control expression of other genes in vivo. The main groups of plant virus genetic elements useful in genetic engineering are reviewed, including the signals for DNA-dependent and RNA-dependent RNA synthesis, sequences on the virus mRNAs that enable translational control, and sequences that control processing and intracellular sorting of virus proteins. Use of plant viruses as extrachromosomal expression vectors is also discussed, along with the issue of their stability.

DNA Replication↗
PubMed1997

State of the art of the production of the antimalarial compound artemisinin in plants.

For more than three centuries we have relied on the extracts of the bark of Cinchona species to treat malaria. Now, it seems we may be changing to the leaves of a Chinese weed, Artemisia annua, and its active compound artemisinin. Artemisinin-derived drugs have been proved particularly effective treatments for severe malaria, even for multidrug-resistant malaria. However, this promising antimalarial compound remains expensive and is hardly available on a global scale. Therefore, many research groups have directed their investigations toward the enhancement of artemisinin production in A. annua cell cultures or whole plants in order to overproduce artemisinin or one of its precursors. This article provides a brief review of the state of art of the different aspects in A. annua research.

Antimalarials↗
PubMed2002

Application of the IFBC/ILSI allergenicity assessment decision tree: an industry perspective.

Three case studies are described; each represents a specific application of the IFBC/ILSI decision tree as prescribed by Metcalfe et al. to assess the allergenic potential of foods derived from genetically engineered crop plants. The case studies include high methionine soybean, high oleic soybean and Herculex TM 1 Insect Protected Maize, the results of which support/validate the use of the IFBC/ILSI decision tree for the prescribed applications.

Allergens↗
PubMed1990

Quantitation of chloramphenicol acetyl transferase in transgenic tobacco plants by ELISA and correlation with gene copy number.

A monoclonal antibody to chloramphenicol acetyl transferase (CAT) was used in an indirect competitive enzyme immunoassay (ELISA) for the quantitation of CAT in leaf extracts of eighteen transgenic tobacco plants containing the CAT gene fused to the cauliflower mosaic virus 35S promoter. The ELISA could be used to quantify CAT when present in extracts at 20 ng/ml. Enzymatic activity and electrophoretic mobility of CAT in these extracts was not different from CAT from Escherichia coli. Concentrations of CAT in these transgenic plants ranged from 79 to 732 ng CAT/mg protein. The average coefficient of variation among three replicate samples was 15%. All plants were sampled on two separate occasions. The CAT concentrations often varied between the two sampling dates. We determined the CAT gene copy number and the number of independently segregating loci in each plant by Southern blot analysis and progeny testing. We found no significant differences in CAT expression among all ten plants with a single CAT gene. We also found a significant correlation between CAT gene copy number and the level of CAT expressed in each plant, although plants with one gene copy sometimes had more CAT than plants with more than one gene copy. In this population, therefore, gene copy number contributed more to the variation in CAT expression than did position effects.

Chloramphenicol O-Acetyltransferase↗
PubMed2001

Expression of an antimicrobial peptide via the chloroplast genome to control phytopathogenic bacteria and fungi.

The antimicrobial peptide MSI-99, an analog of magainin 2, was expressed via the chloroplast genome to obtain high levels of expression in transgenic tobacco (Nicotiana tabacum var. Petit Havana) plants. Polymerase chain reaction products and Southern blots confirmed integration of MSI-99 into the chloroplast genome and achievement of homoplasmy, whereas northern blots confirmed transcription. Contrary to previous predictions, accumulation of MSI-99 in transgenic chloroplasts did not affect normal growth and development of the transgenic plants. This may be due to differences in the lipid composition of plastid membranes compared with the membranes of susceptible target microbes. In vitro assays with protein extracts from T(1) and T(2) plants confirmed that MSI-99 was expressed at high levels to provide 88% (T(1)) and 96% (T(2)) inhibition of growth against Pseudomonas syringae pv tabaci, a major plant pathogen. When germinated in the absence of spectinomycin selection, leaf extracts from T(2) generation plants showed 96% inhibition of growth against P. syringae pv tabaci. In addition, leaf extracts from transgenic plants (T(1)) inhibited the growth of pregerminated spores of three fungal species, Aspergillus flavus, Fusarium moniliforme, and Verticillium dahliae, by more than 95% compared with non-transformed control plant extracts. In planta assays with the bacterial pathogen P. syringae pv tabaci resulted in areas of necrosis around the point of inoculation in control leaves, whereas transformed leaves showed no signs of necrosis, demonstrating high-dose release of the peptide at the site of infection by chloroplast lysis. In planta assays with the fungal pathogen, Colletotrichum destructivum, showed necrotic anthracnose lesions in non-transformed control leaves, whereas transformed leaves showed no lesions. Genetically engineering crop plants for disease resistance via the chloroplast genome instead of the nuclear genome is desirable to achieve high levels of expression and to prevent pollen-mediated escape of transgenes.

Adaptation, Physiological↗
PubMed2006

Metabolic engineering of cell cultures versus whole plant complexity in production of bioactive monoterpene indole alkaloids: recent progress related to old dilemma.

Monoterpene indole alkaloids (MIAs) are a large class of plant alkaloids with significant pharmacological interest. The sustained production of MIAs at high yields is an important goal in biotechnology. Intensive effort has been expended toward the isolation, cloning, characterization and transgenic modulation of genes involved in MIA biosynthesis and in the control of the expression of these biosynthesis-related genes. At the same time, considerable progress has been made in the detailed description of the subcellular-, cellular-, tissue- and organ-specific expressions of portions of the biosynthetic pathways leading to the production of MIAs, revealing a complex picture of the transport of biosynthetic intermediates among membrane compartments, cells and tissues. The identification of the particular environmental and ontogenetic requirements for maximum alkaloid yield in MIA-producing plants has been useful in improving the supply of bioactive molecules. The search for new bioactive MIAs, particularly in tropical and subtropical regions, is continuously increasing the arsenal for therapeutic, industrially and agriculturally useful molecules. In this review we focus on recent progress in the production of MIAs in transgenic cell cultures and organs (with emphasis on Catharanthus roseus and Rauvolfia serpentina alkaloids), advances in the understanding of in planta spatial-temporal expression of MIA metabolic pathways, and on the identification of factors capable of modulating bioactive alkaloid accumulation in nontransgenic differentiated cultures and plants (with emphasis on new MIAs from Psychotria species). The combined use of metabolic engineering and physiological modulation in transgenic and wild-type plants, although not fully exploited to date, is likely to provide the sustainable and rational supply of bioactive MIAs needed for human well being.

Biotechnology↗
PubMed2006

Isolation and characterization of root-specific phosphate transporter promoters from Medicago trunatula.

Promoters of phosphate transporter genes MtPT1 and MtPT2 of Medicago truncatula were isolated by utilizing the gene-space sequence information and by screening of a genomic library, respectively. Two reporter genes, beta-glucuronidase (GUS) and green fluorescent protein (GFP) were placed under the control of the MtPT1 and MtPT2 promoters. These chimeric transgenes were introduced into Arabidopsis thaliana and transgenic roots of M. truncatula, and expression patterns of the reporter genes were assayed in plants grown under different phosphate (Pi) concentrations. The expression of GUS and GFP was only observed in root tissues, and the levels of expression decreased with increasing concentrations of Pi. GUS activities in roots of transgenic plants decreased 10-fold when the plants were transferred from 10 microM to 2 mM Pi conditions, however, when the plants were transferred back to 10 microM Pi conditions, GUS expression reversed back to the original level. The two promoters lead to different expression patterns inside root tissues. The MtPT1 promoter leads to preferential expression in root epidermal and cortex cells, while MtPT2 promoter results in strong expression in the vascular cylinder in the center of roots. Promoter deletion analyses revealed possible sequences involved in root specificity and Pi responsiveness. The promoters are valuable tools for defined engineering of plants, particularly for root-specific expression of transgenes.

Arabidopsis↗
PubMed1998

Gene expression regulated by gene VI of caulimovirus: transactivation of downstream genes of transcripts by gene VI of peanut chlorotic streak virus in transgenic tobacco.

Here we document that the gene VI product of peanut chlorotic streak virus (PClSV), a newly characterized member of the group, transactivates the translation of dicistronic transcripts. Dicistronic expression units have been analyzed both in protoplast transient expression experiments and in transgenic tobacco plants. Transgenic plants containing a dicistronic transcription unit (PClSV-gene VII-GUS) under the control of PClSV full-length transcript promoter with its long leader sequence show a relatively high abundance of the expected transcript but very little, or no, GUS activity. However, high GUS activity is found when gene VI protein is then provided by subsequent infection with PClSV. The efficient translation of polycistronic mRNAs mediated by gene VI of caulimovirus has potential value in product engineering of plants.

Base Sequence↗
PubMed2004

Phytoestrogens.

Collectively, plants contain several different families of natural products among which are compounds with weak estrogenic or antiestrogenic activity toward mammals. These compounds, termed phytoestrogens, include certain isoflavonoids, flavonoids, stilbenes, and lignans. The best-studied dietary phytoestrogens are the soy isoflavones and the flaxseed lignans. Their perceived health beneficial properties extend beyond hormone-dependent breast and prostate cancers and osteoporosis to include cognitive function, cardiovascular disease, immunity and inflammation, and reproduction and fertility. In the future, metabolic engineering of plants could generate novel and exquisitely controlled dietary sources with which to better assess the potential health beneficial effects of phytoestrogens.

Diet↗
PubMed2005

The production of very-long-chain PUFA biosynthesis in transgenic plants: towards a sustainable source of fish oils.

There is now considerable evidence of the importance of n-3 long-chain PUFA in human health and development. At the same time, the marine fish stocks that serve as the primary sources of these fatty acids are threatened by continued over-exploitation. Thus, there is an urgent need to provide a sustainable alternative source of the n-3 long-chain PUFA normally found in fish oils. The possibility of using transgenic plants genetically engineered to synthesise these important fatty acids has recently been demonstrated. The approaches taken to realise this outcome will be discussed, as will their prospects for providing a sustainable resource for the future.

Animals↗
PubMed2001

The future of transgenic plants in developing countries.

Whatever their own policies may be, developing countries will inevitably be affected by the development of genetically-modified organisms in industrialized countries. While maintaining a cautious attitude, most of these countries wish to keep their options open, thus protecting themselves from the risk of being deprived of future technologies that might allow them to achieve self-sufficiency in food production, to resolve certain problems confronting their most vulnerable populations and to preserve the international competitiveness of their products. Companies should see that it is in their interest to help these countries implement their own policies, notably through an open attitude to industrial property. If the value of genetic engineering is thus confirmed, then it perhaps in this manner that GMOs will earn the legitimacy required to make them acceptable to the people of Northern countries where the majority of solvent markets are located.

Agriculture↗
PubMed1990

Opportunities for bioactive compounds in transgenic plants.

A variety of bioactive compounds have now been introduced into plants through recombinant DNA techniques. Early examples included genes encoding proteins conferring herbicide tolerance and insect or virus resistance. More recently, pharmacologically useful compounds such as enkephalin and immunoglobulin have been produced in transgenic plants. Modification of existing compounds to provide better nutritional value or improved functional properties is exemplified in the case of seed storage proteins. The value of RNAs as bioactive compounds for suppression of undesirable products and viral infection has now been demonstrated in plants. The developmentally regulated expression of novel bioactive compounds in defined tissues, and their targeting to specific subcellular locations, is becoming of ever increasing economic and sociological importance as knowledge of the molecular mechanisms involved accumulates.

Endopeptidases↗
PubMed2004

Plant protoplasts: status and biotechnological perspectives.

Plant protoplasts ("naked" cells) provide a unique single cell system to underpin several aspects of modern biotechnology. Major advances in genomics, proteomics, and metabolomics have stimulated renewed interest in these osmotically fragile wall-less cells. Reliable procedures are available to isolate and culture protoplasts from a range of plants, including both monocotyledonous and dicotyledonous crops. Several parameters, particularly the source tissue, culture medium, and environmental factors, influence the ability of protoplasts and protoplast-derived cells to express their totipotency and to develop into fertile plants. Importantly, novel approaches to maximise the efficiency of protoplast-to-plant systems include techniques already well established for animal and microbial cells, such as electrostimulation and exposure of protoplasts to surfactants and respiratory gas carriers, especially perfluorochemicals and hemoglobin. However, despite at least four decades of concerted effort and technology transfer between laboratories worldwide, many species still remain recalcitrant in culture. Nevertheless, isolated protoplasts are unique to a range of experimental procedures. In the context of plant genetic manipulation, somatic hybridisation by protoplast fusion enables nuclear and cytoplasmic genomes to be combined, fully or partially, at the interspecific and intergeneric levels to circumvent naturally occurring sexual incompatibility barriers. Uptake of isolated DNA into protoplasts provides the basis for transient and stable nuclear transformation, and also organelle transformation to generate transplastomic plants. Isolated protoplasts are also exploited in numerous miscellaneous studies involving membrane function, cell structure, synthesis of pharmaceutical products, and toxicological assessments. This review focuses upon the most recent developments in protoplast-based technologies.

Biotechnology↗
PubMed2025

Efficient site-specific integration of kilobase-length DNA fragments in plant cells via Kp03 recombinase.

Targeted insertion of large DNA sequences into plant genomes remains a major challenge in synthetic biology. Here, we evaluate the large serine recombinase Kp03 for site-specific integration of DNA fragments in rice and Arabidopsis. In transient protoplast assays, Kp03 mediates efficient insertion of donor DNA up to 27.3 kilobases (kb), with plasmid integration efficiencies reaching 99.1% for fragments up to 3.4 kb. Truncation experiments reveal that a minimal 15-bp attB sequence is necessary for integration. As a proof of concept, Kp03 successfully incorporates a 3.4-kb donor DNA into the rice genome at a locus containing this minimal attB sequence. Moreover, in rice callus, combining Kp03 with the NM-PE genome editing system to install a 26-bp attB site enables targeted integration of a 3.4-kb donor at the desired genomic locus. These findings establish Kp03 as a versatile tool for plant genome engineering, with broad applications for synthetic biology.

Oryza↗
PubMed2003

A maize defense-inducible gene is a major facilitator superfamily member related to bacterial multidrug resistance efflux antiporters.

A defense-inducible maize gene was discovered through global mRNA profiling analysis. Its mRNA expression is induced by pathogens and defense-related conditions in various tissues involving both resistant and susceptible interactions. These include Cochliobolus heterostrophus and Cochliobolus carbonum infection, ultraviolet light treatment, the Les9 disease lesion mimic background, and plant tissues engineered to express flavonoids or the avirulence gene avrRxv. The gene was named Zm-mfs1 after it was found to encode a protein related to the major facilitator superfamily (MFS) of intregral membrane permeases. It is most closely related to the bacterial multidrug efflux protein family, typified by the Escherichia coli TetA, which are proton motive force antiporters that export antimicrobial drugs and other compounds, but which can be also involved in potassium export/proton import or potassium re-uptake. Other related plant gene sequences in maize, rice, and Arabidopsis were identified, three of which are introduced here. Among this new plant MFS subfamily, the characteristic MFS motif in cytoplasmic TM2-TM3 loop, and the antiporter family motif in transmembrane domain TM5 are both conserved, however the TM7 and the cytoplasmic TM8-TM9 loop are divergent from those of the bacterial multidrug transporters. We hypothesize that Zm-Mfs1 is a prototype of a new class of plant defense-related proteins that could be involved in either of three nonexclusive roles: (1) export of antimicrobial compounds produced by plant pathogens; (2) export of plant-generated antimicrobial compounds; and (3) potassium export and/or re-uptake, as can occur in plant defense reactions.

Amino Acid Sequence↗