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At least 487 records · Page 27Linked to original sources
PubMed2005

Gene stacking in transgenic plants--the challenge for 21st century plant biotechnology.

One of the major technical hurdles impeding the advance of plant genetic engineering and biotechnology is the fact that the expression or manipulation of multiple genes in plants is still difficult to achieve. Although a small proportion of commercial genetically modified (GM) crops present 'stacked' or 'pyramided' traits, only a handful of products have been developed by introducing three or more novel genes. On the research front, a variety of conventional and more novel methods have been employed to introduce multiple genes into plants, but all techniques suffer from certain drawbacks. In this review, the potential and problems of these various techniques and strategies are discussed, and the prospects for improving these technologies in the future are presented.

Journal Article↗
PubMed2006

Improving potato storage and processing characteristics through all-native DNA transformation.

The dominant potato (Solanum tuberosum) variety for French fry production in the United States is the 131-year-old Russet Burbank. Market penetration of the higher yielding and more uniform Ranger Russet variety is limited to about one-fifth of that of the Russet Burbank because of two storage deficits: black spot bruise sensitivity and high levels of cold-induced sweetening. Here, these trait weaknesses are turned into strengths by simultaneously lowering the expression of Ranger Russet's tuber-expressed polyphenol oxidase (Ppo), starch-associated R1, and phosphorylase-L (PhL) genes. This genetic modification was accomplished without inserting any foreign DNA into the plant genome. French fries from the intragenic potatoes also contained reduced amounts of the antinutritional compound acrylamide while, unexpectedly, displaying enhanced sensory characteristics.

DNA, Plant↗
PubMed2003

Plant-centered biosystems in space environments: technological concepts for developing a plant genetic assessment and control system.

Plants will play an essential role in providing life support for any long-term space exploration or habitation. We are evaluating the feasibility of an adaptable system for measuring the response of plants to any unique space condition and optimizing plant performance under those conditions. The proposed system is based on a unique combination of systems including the rapid advances in the field of plant genomics, microarray technology for measuring gene expression, bioinformatics, gene pathways and networks, physiological measurements in controlled environments, and advances in automation and robotics. The resulting flexible module for monitoring and optimizing plant responses will be able to be inserted as a cassette into a variety of platforms and missions for either experimental or life support purposes. The results from future plant functional genomics projects have great potential to be applied to those plant species most likely to be used in space environments. Eventually, it will be possible to use the plant genetic assessment and control system to optimize the performance of any plant in any space environment. In addition to allowing the effective control of environmental parameters for enhanced plant productivity and other life support functions, the proposed module will also allow the selection or engineering of plants to thrive in specific space environments. The proposed project will advance human exploration of space in the near- and mid-term future on the International Space Station and free-flying satellites and in the far-term for longer duration missions and eventual space habitation.

Agriculture↗
PubMed1983

Regeneration of intact tobacco plants containing full length copies of genetically engineered T-DNA, and transmission of T-DNA to R1 progeny.

Cloned DNA sequences encoding yeast alcohol dehydrogenase and a bacterial neomycin phosphotransferase have been inserted into the T-DNA of Agrobacterium tumefaciens plasmid pTiT37 at the "rooty" locus. Transformation of tobacco stem segments with the engineered bacterial strains produced attenuated crown gall tumors that were capable of regeneration into intact, normal tobacco plants. The yeast gene and entire transferred DNA (T-DNA) were present in the regenerated plants in multiple copies, and nopaline was found in all tissues. The plants were fertile, and seedlings resulting from self-pollination also contained intact and multiple copies of the engineered T-DNA. Expression of nopaline in the germinated seedlings derived from one regenerated plant was variable and did not correlate with the levels of T-DNA present in the seedlings. Preliminary evidence indicates that nopaline in progeny of other similarly engineered plants is more uniform. The disarming of pTiT37 by insertions at the "rooty" locus thus appears to produce a useful gene vector for higher plants.

Alcohol Oxidoreductases↗
PubMed1999

Plant 'hairy root' culture.

Due to their fast growth rates and biochemical stability, 'hairy root' cultures remain unsurpassed as the choice for model root systems and have promise as a bioprocessing system. Applications are wide-ranging, from the production of natural products and foreign proteins to a model for phytoremediation of organic and metal contaminants. Hairy roots will have a continuing role as an experimental model in plant metabolic engineering.

Biodegradation, Environmental↗
PubMed2003

A long-term study of knowledge, risk, and ethics for students enrolled in an introductory biotechnology course.

Since 1989, an undergraduate course addressing issues concerning biotechnology in agriculture has been taught annually. To determine the extent to which students were engaged in classroom instruction and assimilated knowledge from the course, students were asked to complete an "Attitudes About Biotechnology" questionnaire. Students were queried about their knowledge of biotechnology, perceptions of risks associated with biotechnology, and ethics and attitudes toward the use of biotechnology in agriculture. Responses to the survey questions were evaluated both pre-and postcourse. Data were collected from 13 classes over a 10-yr period. Inspection of the precourse grade point average and the course grades for these students revealed no trends up or down over the period of this study. Similarly, inspection of the data revealed no effect from problem-based learning, student-facilitated group work, or technology on student attainment of knowledge, perception of risk, or ethical views. For each of the five knowledge questions, the average score increased as a result of taking the course. On two of the knowledge questions, the average score increase for females from pre- to postcourse was greater than for males. Based on our measurements using the postcourse questionnaire, the correlation between perceived and actual knowledge was not significantly different from zero. In two of the four risk questions, there was no change in average score as a result of the course; however, student perception of risk associated with genetic engineering of plants increased. Although average scores for student perception of risk due to the perceived impact of genetically engineered products on people or the environment decreased from pre- to postcourse assessment, the average score was higher (P < 0.01) for females than for males. Males were more accepting of genetic manipulation of cells in a laboratory than were females both pre- and postcourse. Although student knowledge of biotechnology was increased and the perceived risk due to biotechnology was altered, there was no evidence that students altered their ethical position on biotechnology as a result of this course.

Adult↗
PubMed2002

Recombinase-directed plant transformation for the post-genomic era.

Plant genomics promises to accelerate genetic discoveries for plant improvements. Machine-driven technologies are ushering in gene structural and expressional data at an unprecedented rate. Potential bottlenecks in this crop improvement process are steps involving plant transformation. With few exceptions, genetic transformation is an obligatory final step by which useful traits are engineered into plants. In addition, transgenesis is most often needed to confirm gene function, after deductions made through comparative genomics, expression profiles, and mutation analysis. This article reviews the use of recombinase systems to deliver DNA more efficiently into the plant genome.

Base Sequence↗
PubMed2002

Plant toxic proteins with insecticidal properties. A review on their potentialities as bioinsecticides.

To meet the demands for food of the expanding world population, there is need of new ways for protecting plant crops against predators and pathogens while avoiding the use of environmentally aggressive chemicals. A milestone in this field was the introduction into crop plants of genes expressing Bacillus thuringiensis entomotoxic proteins. In spite of the success of this new technology, however, there are difficulties for acceptance of these 'anti-natural' products by the consumers and some concerns about its biosafety in mammals. An alternative could be exploring the plant's own defense mechanisms, by manipulating the expression of their endogenous defense proteins, or introducing an insect control gene derived from another plant. This review deals with the biochemical features and mechanisms of actions of plant proteins supposedly involved in defense mechanisms against insects, including lectins, ribosome-inactivating proteins, enzymes inhibitors, arcelins, chitinases, ureases, and modified storage proteins. The potentialities of genetic engineering of plants with increased resistance to insect predation relying on the repertoire of genes found in plants are also discussed. Several different genes encoding plant entomotoxic proteins have been introduced into crop genomes and many of these insect resistant plants are now being tested in field conditions or awaiting commercialization.

Amino Acid Sequence↗
PubMed2006

Directed microspore-specific recombination of transgenic alleles to prevent pollen-mediated transmission of transgenes.

A major challenge for future genetically modified (GM) crops is to prevent undesired gene flow of transgenes to plant material intended for another use. Recombinase-mediated auto excision of transgenes directed by a tightly controlled microspore-specific promoter allows efficient removal of either the selectable marker gene or of all introduced transgenes during microsporogenesis. This way, transgene removal becomes an integral part of the biology of pollen maturation, not requiring any external stimulus such as chemical induction by spraying. We here show the feasibility of engineering transgenic plants to produce pollen devoid of any transgene. Highly efficient excision of transgenes from tobacco pollen was achieved with a potential failure rate of at most two out of 16,800 seeds (0.024%). No evidence for either premature activation or absence of activation of the recombinase system was observed under stress conditions in the laboratory. This approach can prevent adventitious presence of transgenes in non-GM crops or related wild species by gene flow. Such biological containment may help the deployment and management of coexistence practices to support consumer choice and will promote clean molecular farming for the production of high-value compounds in plants.

Alleles↗
PubMed2005

Purification of transgenic plant-derived recombinant human acetylcholinesterase-R.

Nicotiana benthamiana plants were engineered to express a codon-optimized gene encoding the human acetylcholinesterase-R (AChE) isoform. The transgenic plants expressed the protein at >0.4% of total soluble protein, and the plant-produced enzyme was purified to homogeneity. Following lysis, procainamide affinity chromatography and anion-exchange chromatography, more than 400-fold purification was achieved and electrophoretic purity was obtained. This pure protein is kinetically indistinguishable from the only commercially available source of human acetylcholinesterase, which is produced in mammalian cell culture. Thus, we have demonstrated a model system for the production of acetylcholinesterase, which is not susceptible to the quantitative limitations or mammalian pathogens associated with purification from mammalian cell culture or human serum.

Acetylcholinesterase↗
PubMed1998

Plant cell walls as targets for biotechnology.

Plants are the sources of major food, feed, and fiber products that are used globally. This past year has seen advances in our understanding of the enzymes that modify wall architecture, the cloning of the first cellulose synthase gene, and revisions to the lignin biosynthetic pathway. These discoveries have facilitated the development of new strategies to alter cell wall properties in transgenic plants.

Biotechnology↗
PubMed1999

Production of recombinant proteins in plant root exudates.

The large-scale production of recombinant proteins in plants is limited by relatively low yields and difficulties in extraction and purification. These problems were addressed by engineering tobacco plants to continuously secrete recombinant proteins from their roots into a simple hydroponic medium. Three heterologous proteins of diverse origins (green fluorescent protein of jellyfish, human placental alkaline phosphatase [SEAP], and bacterial xylanase) were produced using the root secretion method (rhizosecretion). Protein secretion was dependent on the presence of the endoplasmic reticulum signal peptide fused to the recombinant protein sequence. All three secreted proteins retained their biological activity and, as shown for SEAP, accumulated in much higher amounts in the medium than in the root tissue.

Alkaline Phosphatase↗
PubMed2005

Spatial prediction of corn rootworm (Coleoptera: Chrysomelidae) adult emergence in Iowa cornfields.

The most common management options for corn rootworms are rotating corn with nonhost crops, planting genetically engineered corn resistant to corn rootworms (e.g., Bacillus thuringiensis [Bt] corn), and treating with a soil insecticide at planting time. Because these control tactics are preventive, the decision to apply controls has been made without any knowledge of rootworm density and spatial distribution. This study was conducted to predict the spatial distribution of adult emergence and to generate and test management zones for insecticides and Bt corn. To identify variables that correlated best with adult emergence the following year, plant height, plant stage, soil moisture, altitude, and corn rootworm adults were sampled spatially and temporally. Correlation and regression analyses showed that the best prediction for the adult emergence the following year was adult counts in the ear zone at peak population densities during the present year. Based on the prediction, geostatistics and the geographic information system were used to generate and test prescription maps with management zones for insecticides and Bt corn. Map-overlaying analysis showed that management zones for insecticides based on the economic injury level and Bt corn with 20% refuge had potential failure of 3-15% and 0-12% of field areas, respectively. This study demonstrated the spatial prediction of adult emergence the following year and generation of management zones, which has the potential of preventative, site-specific management of corn rootworms.

Agriculture↗
PubMed2001

Developing tools for phytoremediation: towards a molecular understanding of plant metal tolerance and accumulation.

Certain plant species and genotypes are able to accumulate large quantities of heavy metals in their shoots. Based on this trait the concept of phytoremediation was developed, i.e. the use of metal hyperaccumulating plants for the cleansing of contaminated soils and water. In order to more efficiently use this capacity, an engineering of plants might be needed. However, very little is known about the underlying molecular mechanisms. Our work is focussing on the identification and characterization of plant genes involved in plant metal uptake, tolerance and accumulation. Phytochelatins are small glutathione-derived metal-binding peptides which are part of the plant metal detoxification system. Genes encoding phytochelatin synthases have been cloned and are now being studied with regard to their regulation, biochemistry and biotechnological potential. Another project aimes at the dissection of metal responses in the metallophyte Arabidopsis halleri. This plant, a close relative to the model plant Arabidopsis thaliana, is Cd hypertolerant and Zn hyperaccumulating. It grows, for instance, on medieval mining sites in the Harz mountains in Germany and in many other metal-contaminated sites in Central Europe. We have isolated metal-regulated genes from A. halleri and molecularly analyzed interesting candidate genes with regard to their function and involvement in metal accumulation and tolerance.

Biotechnology↗
PubMed1994

Metabolic engineering of glycine betaine synthesis: plant betaine aldehyde dehydrogenases lacking typical transit peptides are targeted to tobacco chloroplasts where they confer betaine aldehyde resistance.

Certain higher plants synthesize and accumulate glycine betaine, a compound with osmoprotectant properties. Biosynthesis of glycine betaine proceeds via the pathway choline-->betaine aldehyde-->glycine betaine. Plants such as tobacco (Nicotiana tabacum L.) which do not accumulate glycine betaine lack the enzymes catalyzing both reactions. As a step towards engineering glycine betaine accumulation into a non-accumulator, spinach and sugar beet complementary-DNA sequences encoding the second enzyme of glycine-betaine synthesis (betaine aldehyde dehydrogenase, BADH, EC 1.2.1.8) were expressed in tobacco. Despite the absence of a typical transit peptide, BADH was targeted to the chloroplast in leaves of transgenic plants. Levels of extractable BADH were comparable to those in spinach and sugar beet, and the molecular weight, isoenzyme profile and Km for betaine aldehyde of the BADH enzymes from transgenic plants were the same as for native spinach or sugar beet BADH. Transgenic plants converted supplied betaine aldehyde to glycine betaine at high rates, demonstrating that they were able to transport betaine aldehyde across both the plasma membrane and the chloroplast envelope. The glycine betaine produced in this way was not further metabolized and reached concentrations similar to those in plants which accumulate glycine betaine naturally. Betaine aldehyde was toxic to non-transformed tobacco tissues whereas transgenic tissues were resistant due to detoxification of betaine aldehyde to glycine betaine. Betaine aldehyded ehydrogenase is therefore of interest as a potential selectable marker, as well as in the metabolic engineering of osmoprotectant biosynthesis.

Aldehyde Oxidoreductases↗
PubMedDate not supplied

PHA production, from bacteria to plants.

The genes encoding the polyhydroxyalkanoate (PHA) biosynthetic pathway in Ralstonia eutropha (3-ketothiolase, phaA or bktB; acetoacetyl-CoA reductase, phaB; and PHA synthase, phaC) were engineered for plant plastid targeting and expressed using leaf (e35S) or seed-specific (7s or lesquerella hydroxylase) promoters in Arabidopsis and Brassica. PHA yields in homozygous transformants were 12-13% of the dry mass in homozygous Arabidopsis plants and approximately 7% of the seed weight in seeds from heterozygous canola plants. When a threonine deaminase was expressed in addition to bktB, phaB and phaC, a copolyester of 3-hydroxybutyrate and 3-hydroxyvalerate was produced in both Arabidopsis and Brassica.

Acetyl-CoA C-Acyltransferase↗
PubMed2005

[Advances in the Study on Marker Genes in transgenic Plants.].

Plant transgenic engineering is becoming more and more important in the world. The safety of selectable marker genes in the transgenic plants has been noticed widely. The new advances of selectable markers in transgenic plants were reviewed in this paper in three aspects. The first is the establishment of transformation systems allowing resistant marker genes to be eliminated from the transgenic plants, including co-transformation, site-specific recombination and transposition, as well as other methods. In these ways, the transgenes can be inserted into transgenic plants more than once. The second is the utilization and development of bio-safe positively selective marker genes, mainly referred to the carbohydrates metabolism genes, the stress- resistant enzymatic genes and the green fluorescent protein(GFP) gene. At the same time, the mercuric reductase genes, the key genes for chloroplast synthesis and other genes should also be quickly developed as markers. The third is the establishment of marker-free and skelecton-free transformation vector systems, which are efficient and simple. The prospects in application of these novel methods, marker free and safe selectable markers are also viewed in the article.

Genetic Markers↗