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At least 199 records · Page 11Linked to original sources
PubMed1997

Modification of plant components.

With respect to plant biotechnology, 1995 and 1996 will be marked by the commercialization of the first genetically engineered plant oil and a number of ground-breaking publications. The modification of plant components using transgenic technology is not just 'switching' phenotypes from one host to another, rather, it is a means for producing valuable novel products that are normally not found (or are difficult to find) in plants. Active research is being carried out with similar schemes in both academic laboratories and biotechnology companies. As a result, the traditional line that separates the 'basic' research of universities and the 'practical' work of industry is becoming fuzzy. Although many roadblocks remain, judging from the progress made in the past two years, the genetic engineering of plant components is heading towards a bright and exciting future.

Journal Article↗
PubMed2006

A mathematical model of plants as ecosystem engineers.

Understanding the structure and dynamics of plant communities in water-limited systems often calls for the identification of ecosystem engineers--key species that modify the landscape, redistribute resources and facilitate the growth of other species. Shrubs are excellent examples; they self-organize to form patterns of mesic patches which provide habitats for herbaceous species. In this paper we present a mathematical model for studying ecosystem engineering by woody plant species in drylands. The model captures various feedbacks between biomass and water including water uptake by plants' roots and increased water infiltration at vegetation patches. Both the uptake and the infiltration feedbacks act as mechanisms for vegetation pattern formation, but have opposite effects on the water resource; the former depletes the soil-water content under a vegetation patch, whereas the latter acts to increase it. Varying the relative strength of the two feedbacks we find a trade-off between the engineering capacity of a plant species and its resilience to disturbances. We further identify two basic soil-water distributions associated with engineering at the single patch level, hump-shaped and ring-shaped, and discuss the niches they form for herbaceous species. Finally, we study how pattern transitions at the landscape level feedback to the single patch level by affecting engineering strength.

Biomass↗
PubMed2002

A novel bioremediation system for heavy metals using the symbiosis between leguminous plant and genetically engineered rhizobia.

A novel plant-bacterial remediation system for heavy metals (HM) was developed by expression of tetrameric human metallothionein (MTL4) in Mesorhizobium huakuii subsp. rengei B3, a strain which infects and forms nodules on a green manure, Astragalus sinicus. The MTL4 gene was fused to the nifH and nolB promoters, which generated nodule- specific expression of the MTL4 gene. The expression analysis of the MTL4 gene was demonstrated in free-living cells in the presence of Cd(2+) and Cu(2+), under the low oxygen condition. The MTL4 under the nifH and nolB promoters was expressed and increased the accumulation of Cd(2+), but not Cu(2+) in free-living cells. The expression of the integrated nifH-MTL4 gene in the chromosome of strain B3 was also expressed stably and accumulated Cd(2+) in the bacterial cells. The MTL4 transcripts were detected by in situ hybridization in bacteroids of mature nodules of A. sinicus containing nifH-MTL4 and nolB-MTL4 fusion gene. Moreover the MTL4 protein was detected by immunostaining. By infection of the recombinant B3, A. sinicus established symbiosis with the recombinant B3 that was grown in Cd(2+) and Cu(2+)-polluted soils. The symbionts increased Cd(2+) accumulation in nodules 1.7-2.0-fold, whereas, no significantly increase in Cu(2+) accumulation was noted.

Astragalus Plant↗
PubMed2004

Overexpression of the acidic dehydrin WCOR410 improves freezing tolerance in transgenic strawberry leaves.

Progress in freezing tolerance (FT) improvement through plant breeding approaches has met with little success in the last 50 years. Engineering plants for greater FT through plant transformation is one possible way to reduce the damage caused by freezing. Here, we report an improvement of the selection procedure and the transfer of the wheat Wcor410a acidic dehydrin gene in strawberry. The encoded protein has previously been shown to be associated with the plasma membrane, and its level of accumulation has been correlated with the degree of FT in different wheat genotypes. The WCOR410 protein was expressed in transgenic strawberry at a level comparable with that in cold-acclimated wheat. Freezing tests showed that cold-acclimated transgenic strawberry leaves had a 5 degrees C improvement of FT over wild-type or transformed leaves not expressing the WCOR410 protein. However, no difference in FT was found between the different plants under non-acclimated conditions, suggesting that the WCOR410 protein needs to be activated by another factor induced during cold acclimation. These data demonstrate that the WCOR410 protein prevents membrane injury and greatly improves FT in leaves of transgenic strawberry. A better understanding of the limiting factors allowing its activation may open up the way for engineering FT in different plant organs, and may find applications for the cryopreservation of human tissues and organs.

Journal Article↗
PubMed1999

Improving nutrient capture from soil by the genetic manipulation of crop plants

Modern agricultural practices require the massive application of fertilizer to soils worldwide. In the USA alone, millions of tons of fertilizer are applied to agricultural soils each year. The adverse environmental impact and high cost of fertilizer use underscore the importance of improving the capability of plants to capture nutrients from soil. Therefore, engineering plants with improved micronutrient uptake may help in creating sustainable agriculture in the next century.

Journal Article↗
PubMed2002

Dynamic simulation of chemical industry wastewater treatment plants.

High variability, stringent effluent permits, and often extreme operating conditions define the practice of wastewater treatment in the chemical industry. This paper reviews the benefits and challenges of applying dynamic simulation to chemical-industry wastewater treatment plants by describing case studies at full-scale wastewater treatment plants (WWTP). The applications range from process troubleshooting to optimization and control. The applications have been valuable and useful in developing a deeper understanding of the plants as integrated systems. However there still remains substantial work to implement the dynamic simulations for daily real-time use by plant engineers and operators. This opportunity to improve plant operations is still largely untapped and will remain so until dynamic state estimation and data reconciliation are incorporated into simulation packages for use in developing the on-line simulations.

Bioreactors↗
PubMed2006

[Progress in the study on conditional male sterility in plants by genetic engineering].

Conditional (reversible) male sterile line in plants would be fertile under special conditions, and thus could be used as two-line to produce hybrid seeds. This paper described the strategies for creating conditional male sterile line and correspondingly restoring it. Some related problems about the issue were commented on. In addition, this review also predicted the prospects of the study on conditional male sterility.

Genes, Plant↗
PubMed2005

Gene expression changes in Arabidopsis thaliana seedling roots exposed to the munition hexahydro-1,3,5-trinitro-1,3,5-triazine.

Arabidopsis thaliana root transcriptome responses to the munition, hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), were assessed using serial analysis of gene expression (SAGE). Sequencing of SAGE libraries from control and RDX-exposed root tissues revealed induction of genes known to respond to a variety of general stresses. Among the highly induced genes were several encoding molecular chaperones and transcription factors as well as vacuolar proteins and peroxidases. Strongly repressed transcripts included ones encoding ribosomal proteins, a cyclophilin, a katanin, and a peroxidase. Comparison of the transcriptional profile for the RDX response to a profile previously described for Arabidopsis roots exposed to trinitrotoluene (TNT) revealed significant differences in the inferred gene expression patterns. This suggests that Arabidopsis employs drastically different mechanisms for coping with these two compounds. With respect to the goal of engineering plants to better tolerate and degrade explosives at contaminated sites, these results suggest that enhancement of different genes and metabolic pathways may be required to deal effectively with each type of explosive. This has ramifications for phytoremediation efforts since many contaminated sites harbor both compounds.

Adaptation, Physiological↗
PubMed2006

Peptide display on Potato virus X: molecular features of the coat protein-fused peptide affecting cell-to-cell and phloem movement of chimeric virus particles.

The potexvirus Potato virus X (PVX) can be modified genetically to generate chimeric virus particles (CVPs) carrying heterologous peptides fused to coat protein (CP) subunits. A spontaneous PVX mutant expressing a truncated, but functional, form of the CP has been isolated. With the aim of exploiting this virus to display peptides useful for vaccine formulations, two novel viral expression vectors based on pPVX201 (bearing the wild-type PVX genome) were constructed encoding the truncated CP. Both vectors were able to produce infectious virus particles in planta and were used to insert a panel of sequences encoding peptides of biopharmaceutical interest as N-terminal fusions to the truncated cp gene. The analysis of infection progression induced by the different constructs enabled identification of two important structural features of the fused peptide, namely tryptophan content and isoelectric point, critically affecting the formation of PVX CVPs and virus movement through the plant. These results are discussed in view of the rising interest in engineered plant viruses for development of peptide-based epitope vaccines.

Capsid Proteins↗
PubMed2006

Mucosal immunization using recombinant plant-based oral vaccines.

The induction of mucosal immunity is very important in conferring protection against pathogens that typically invade via mucosal surfaces. Delivery of a vaccine to a mucosal surface optimizes the induction of mucosal immunity. The apparent linked nature of the mucosal immune system allows delivery to any mucosal surface to potentially induce immunity at others. Oral administration is a very straightforward and inexpensive approach to deliver a vaccine to the mucosal lining of the gut. However, vaccines administered by this route are subject to proteolysis in the gastrointestinal tract. Thus, dose levels for protein subunit vaccines are likely to be very high and the antigen may need to be protected from proteolysis for oral delivery to be efficacious. Expression of candidate vaccine antigens in edible recombinant plant material offers an inexpensive means to deliver large doses of vaccines in encapsulated forms. Certain plant tissues can also stably store antigens for extensive periods of time at ambient temperatures, obviating the need for a cold-chain during vaccine storage and distribution, and so further limiting costs. Antigens can be expressed from transgenes stably incorporated into a host plant's nuclear or plastid genome, or from engineered plant viruses infected into plant tissues. Molecular approaches can serve to boost expression levels and target the expressed protein for appropriate post-translational modification. There is a wide range of options for processing plant tissues to allow for oral delivery of a palatable product. Alternatively, the expressed antigen can be enriched or purified prior to formulation in a tablet or capsule for oral delivery. Fusions to carrier molecules can stabilize the expressed antigen, aid in antigen enrichment or purification strategies, and facilitate delivery to effector sites in the gastrointestinal tract. Many antigens have been expressed in plants. In a few cases, vaccine candidates have entered into early phase clinical trials, and in the case of farmed animal vaccines into relevant animal trials.

Administration, Oral↗
PubMed2000

Metabolic modeling identifies key constraints on an engineered glycine betaine synthesis pathway in tobacco.

Previous work has shown that tobacco (Nicotiana tabacum) plants engineered to express spinach choline monooxygenase in the chloroplast accumulate very little glycine betaine (GlyBet) unless supplied with choline (Cho). We therefore used metabolic modeling in conjunction with [(14)C]Cho labeling experiments and in vivo (31)P NMR analyses to define the constraints on GlyBet synthesis, and hence the processes likely to require further engineering. The [(14)C]Cho doses used were large enough to markedly perturb Cho and phosphocholine pool sizes, which enabled development and testing of models with rates dynamically responsive to pool sizes, permitting estimation of the kinetic properties of Cho metabolism enzymes and transport systems in vivo. This revealed that import of Cho into the chloroplast is a major constraint on GlyBet synthesis, the import rate being approximately 100-fold lower than the rates of Cho phosphorylation and transport into the vacuole, with which import competes. Simulation studies suggested that, were the chloroplast transport limitation corrected, additional engineering interventions would still be needed to achieve levels of GlyBet as high as those in plants that accumulate GlyBet naturally. This study reveals the rigidity of the Cho metabolism network and illustrates how computer modeling can help guide rational metabolic engineering design.

Betaine↗
PubMed2005

Overexpression of an Arabidopsis thaliana ABC transporter confers kanamycin resistance to transgenic plants.

Selectable markers of bacterial origin such as the neomycin phosphotransferase type II gene, which can confer kanamycin resistance to transgenic plants, represent an invaluable tool for plant engineering. However, since all currently used antibiotic-resistance genes are of bacterial origin, there have been concerns about horizontal gene transfer from transgenic plants back to bacteria, which may result in antibiotic resistance. Here we characterize a plant gene, Atwbc19, the gene that encodes an Arabidopsis thaliana ATP binding cassette (ABC) transporter and confers antibiotic resistance to transgenic plants. The mechanism of resistance is novel, and the levels of resistance achieved are comparable to those attained through expression of bacterial antibiotic-resistance genes in transgenic tobacco using the CaMV 35S promoter. Because ABC transporters are endogenous to plants, the use of Atwbc19 as a selectable marker in transgenic plants may provide a practical alternative to current bacterial marker genes in terms of the risk for horizontal transfer of resistance genes.

ATP-Binding Cassette Transporters↗
PubMedDate not supplied

Persistence of Agrobacterium tumefaciens in transformed conifers.

Previous studies have shown that the widely used plant transformation vector Agrobacterium tumefaciens can persist in genetically engineered plants in vitro and in transgenic greenhouse-grown plants, despite the use of counter-selective antibiotics. However, little is known regarding Agrobacterium persistence in tree species. To understand the kinetics of A. tumefaciens decline and persistence in transformation experiments, we assayed for the presence of A. tumefaciens in spruce and pine embryogenic tissue for up to 10 weeks post-transformation. The A. tumefaciens populations declined rapidly in the first five days post-cocultivation but generally declined more slowly in pine, relative to spruce. No bacteria were detected in spruce embryogenic tissue beyond four weeks after cocultivation, however in pine there were -100 colony forming units per g tissue at 10 weeks post-cocultivation. We present evidence that the detection limit for PCR using virD2 primers to detect A. tumefaciens in a background of pine needle DNA was approximately 10(9)-10(10) A. tumefaciens cells per g of tissue. We also assayed for A. tumefaciens in transgenic pine and spruce embryogenic tissue and from needles, branches, stems and roots of transformed plants, up to four years post-inoculation. Occasionally A. tumefaciens was detected in embryogenic tissue up to 12 months post-inoculation. A. tumefaciens was never detected in cultured embryogenic tissue more than twelve months after inoculation, nor in developing somatic embryos or germinating plantlets, nor any of the parts of greenhouse-grown plants. From these data we conclude that if A. tumefaciens persists in transgenic conifers, it does so beneath our ability to detect it.

Agrobacterium tumefaciens↗
PubMed2005

Loss of susceptibility as an alternative for nematode resistance.

Among plant pathogens, sedentary endoparasitic nematodes are one of the most damaging pests in global agriculture. These obligate parasites interact with their hosts in a quite unique and intriguing way. They induce the redifferentiation of root cells into specialized feeding cells essential for nematode growth and reproduction; thus, nematodes have evolved the ability to exploit plant genes and hijack host functions for their own requirements. Various approaches to engineer plants with resistance to parasitic nematodes have been pursued, most focusing on the introduction of resistance genes. An alternative strategy to achieve resistance is to exploit the susceptibility of plant disease. Better knowledge of the plant response during the compatible interaction should allow the identification of targets to engineer resistance to parasitic nematodes in crop species.

Alleles↗
PubMed1992

Metabolic engineering of medicinal plants: transgenic Atropa belladonna with an improved alkaloid composition.

The tropane alkaloid scopolamine is a medicinally important anticholinergic drug present in several solanaceous plants. Hyoscyamine 6 beta-hydroxylase (EC 1.14.11.11) catalyzes the oxidative reactions in the biosynthetic pathway leading from hyoscyamine to scopolamine. We introduced the hydroxylase gene from Hyoscyamus niger under the control of the cauliflower mosaic virus 35S promoter into hyoscyamine-rich Atropa belladonna by the use of an Agrobacterium-mediated transformation system. A transgenic plant that constitutively and strongly expressed the transgene was selected, first by screening for kanamycin resistance and then by immunoscreening leaf samples with an antibody specific for the hydroxylase. In the primary transformant and its selfed progeny that inherited the transgene, the alkaloid contents of the leaf and stem were almost exclusively scopolamine. Such metabolically engineered plants should prove useful as breeding materials for obtaining improved medicinal components.

Atropa belladonna↗
PubMed2004

Overexpression of spermidine synthase enhances tolerance to multiple environmental stresses and up-regulates the expression of various stress-regulated genes in transgenic Arabidopsis thaliana.

Polyamines play pivotal roles in plant defense to environmental stresses. However, stress tolerance of genetically engineered plants for polyamine biosynthesis has been little examined so far. We cloned spermidine synthase cDNA from Cucurbita ficifolia and the gene was introduced to Arabidopsis thaliana under the control of the cauliflower mosaic virus 35S promoter. The transgene was stably integrated and actively transcribed in the transgenic plants. As compared with the wild-type plants, the T2 and T3 transgenic plants exhibited a significant increase in spermidine synthase activity and spermidine content in leaves together with enhanced tolerance to various stresses including chilling, freezing, salinity, hyperosmosis, drought, and paraquat toxicity. During exposure to chilling stress (5 degrees C), the transgenics displayed a remarkable increase in arginine decarboxylase activity and conjugated spermidine contents in leaves compared to the wild type. A cDNA microarray analysis revealed that several genes were more abundantly transcribed in the transgenics than in the wild type under chilling stress. These genes included those for stress-responsive transcription factors such as DREB and stress-protective proteins like rd29A. These results strongly suggest an important role for spermidine as a signaling regulator in stress signaling pathways, leading to build-up of stress tolerance mechanisms in plants under stress conditions.

Arabidopsis↗
PubMed1990

Regulation of biotechnology in the United States and Canada.

The regulation of biotechnology in the United States and Canada is based on principles that reflect respect for the new technology, yet also recognize that most traditional approaches to regulation, employing sound science and common sense, still apply. Four specific principles form the framework on which regulatory schemes are based: (1) the products of biotechnology will not differ fundamentally from unmodified organisms or from conventional products; (2) the product rather than the process shall be regulated; (3) regulation should be based on the end use of the product and will be conducted on a case-by-case basis; and (4) the existing laws provide adequate authority for regulating the products of biotechnology. This report summarizes the regulatory approaches taken in various organisms and products. Special emphasis is given to: (1) issuance of entry permits for genetically-engineered plants and micro-organisms; (2) licensing of genetically-engineered veterinary biological products; and (3) permits for movement and release into the environment. A three-category classification system is described for dealing with hybridomas and recombinant-derived products, based on their biological characteristics and safety concerns. Categories range from relatively simple inactivated recombinant animal vaccines to products using live vectors to carry recombinant-derived foreign genes that code for immunizing antigens and/or other immune stimulants. This paper stresses that few fields of contemporary science and technology hold forth more possibilities and greater expectations than biotechnology. It is therefore of utmost importance that animal health officials and scientists ensure that the products of biotechnology will not cause or transmit infectious disease, adversely affect the environment or adulterate food products.

Animals↗
PubMed1997

Future vaccines and a global perspective.

Advances in medical biotechnology mean that vaccines to prevent more than 75 infectious diseases are being or have been developed. Vaccination is unfortunately not reliant purely on biotechnology but also on politics and resources. Countries with the greatest demand for vaccines have the least ability to pay for or produce them. Health-care Infrastructure and diagnostic facilities also hamper immunisation projects in developing countries. Charitable organisations are relied on heavily to support such projects but the challenge to ensure all infants are immunised against the most common infections of childhood is still enormous. Difficulties that present themselves now should not prevent us looking into future possibilities such as immunisation during pregnancy and targeting of children for immunisation against sexually transmitted diseases. Other avenues for research are in administration of vaccines. A move to mucosal immunisation rather than use of the syringe and needle would be positive both economically and from the point of view of risk of needle contamination. Plant science may also provide a new vehicle for vaccines by engineering plants such as the banana tree to be naturally bioencapsulated vaccines. Prospects for control and eradication of infectious disease in the next century are certainly good.

Biotechnology↗