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Duckweed genes are similar to those of other plants. Many laboratories
have cloned (isolated) genes from duckweeds for
research in several areas, particularly photosynthesis and phytochrome regulation of plant development. Elaine
Tobin's lab (UCLA) has studied the regulation of chloroplast development by
phytochrome. Cheryl Smart (ETH,
Bibliography of
Biolex Corporation: Duckweed Genetic Engineering
The desirable characteristics of duckweeds in agriculture and the environment spurred scientists to think of more and more novel uses for these plants. Many of these new applications may require new capabilities for duckweed metabolism, growth or nutritional composition. Genetic modifications will be required to give duckweeds these new characteristics, and the new technology of genetic engineering is a powerful technique that can help bring many of these dreams to reality. This technology is being used to modify the activity of existing duckweed genes, or to introduce new genes into duckweeds.
Pharmaceutical
Proteins from Duckweed.
Some of the most exciting prospects in duckweed technology are aimed at using
this plant as a factory for biopharmaceuticals. The advantages of this
technology are many:
- inexpensive culture techniques,
- complete containment of the culture system,
- easy scale-up from laboratory to factory, and
- freedom from animal materials in the production process.
- glycosylated proteins can be engineered.
The total absence of
potentially hazardous animal proteins, cells and viruses means that many of the
challenges of producing biopharmaceuticals are vastly simplified and the cost
of production reduced accordingly. At first these advantages were merely
theoretical, but now this technology is making rapid strides towards practical
commercialization.
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Stomp estimates the market for pharmaceutical proteins like insulin is
worth about $10 billion yearly. [ Read
the Press Release ] Dr. Stomp made this advance with the aid of an EPA research grant, Genetic Improvement of Duckweed (Lemna gibba) for Wastewater Treatment. The final report of this grant is still available on line. |
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Yamamoto Y.T.*; Rajbhandari N.; Lin X.; Bergmann B.A.; Nishimura Y.; Stomp A.M. (2001) "Genetic transformation of duckweed Lemna gibba and Lemna minor." In Vitro Cellular and Development Biology - Plant, 37(3):349-353. "We developed efficient genetic
transformation protocols for two species of duckweed, Lemna gibba (G3) and
Lemna minor (8627 and 8744), using Agrobacterium-mediated gene
transfer. Partially differentiated nodules were co-cultivated with
Agrobacterium tumefaciens harboring a binary vector containing -glucuronidase
and nptII expression cassettes. Transformed cells were selected and
allowed to grow into nodules in the presence of kanamycin. Transgenic
duckweed fronds were regenerated from selected nodules. We demonstrated
that transgenic duckweed could be regenerated within 3 months after
Agrobacterium-mediated transformation of nodules. Furthermore, we
developed a method for transforming L. minor 8627 in 6 weeks. These
transformation protocols will facilitate genetic engineering of duckweed,
ideal plants for bioremediation and large-scale industrial production of
biomass and recombinant proteins." |
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Duckweed tissue culture research from this lab. H. K. Moon and A. M. Stomp (1996) Effects of Medium Components and Light on Callus Induction, Growth, and Frond Regeneration in Lemna gibba (Duckweed). In Vitro Plant Cellular & Developmental Biology 33(1):20-25.Tamara Lynn Tatroe. (1998) Investigation of growth parameters for a
plant-based gene expression system using duckweed. M.S. Thesis,
Biological and Agricultural Engineering, |
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Identification of superior clones for bioremedation: Bergmann, B.A., Cheng, J., Classen, J., Stomp, A.M. (2000) In vitro selection of duckweed geographical isolates for potential use in swine lagoon effluent renovation. Bioresource technology. 73 (1):13-20.
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Protein Glycosylation Cox KM et al. Glycan optimization of a human monoclonal
antibody in the aquatic plant Lemna minor. Nat Biotechnol. 2006 Dec;24(12):1591-7. “N-glycosylation is
critical to the function of monoclonal antibodies (mAbs) and distinguishes
various systems used for their production. We expressed human mAbs in the
small aquatic plant Lemna minor, which offers several advantages for
manufacturing therapeutic proteins free of zoonotic pathogens. Glycosylation
of a mAb against human CD30 was optimized by co-expressing the heavy and
light chains of the mAb with an RNA interference construct targeting
expression of the endogenous alpha-1,3-fucosyltransferase and
beta-1,2-xylosyltransferase genes. The resultant mAbs contained a single
major N-glycan species without detectable plant-specific N-glycans and had
better antibody-dependent cell-mediated cytotoxicity and effector cell
receptor binding activities than mAbs expressed in cultured Chinese hamster
ovary (CHO) cells.” |
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Biolex Incorporated, Recombinant Protein Technology |
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Biolex is developing processes for producing pharmaceutical proteins in duckweed. Much of the information below comes from the Biolex website.
"Biolex, Inc. is a biotechnology company based in Pittsboro, North Carolina, just outside of Research Triangle Park. Biolex is focused on developing the next generation of patented, recombinant protein production technologies in a plant based system. The foundation of the Biolex technology is its patented Lemna System™. This system couples the natural characteristics of the green plant, Lemna, with advanced genetic engineering and protein recovery methods to create a recombinant protein production platform."
"The Lemna System™ has unique, innate characteristics that provide enormous value for recombinant protein production" The stated advantages include: versatility, efficient genetic engineering, fast and flexible operation, low capital costs for facilities, low operating costs, high protein recovery and simple purification, product safety, and environmental safety.
Biolex is currently working with pharmaceutical companies on production of several important therapeutic proteins, including plasmin, alpha-interferon-2b and human growth hormone. Biolex claims to have successfully expressed twelve recombinant proteins in duckweeds, including small peptides, Fab fragments (Fabs), monoclonal antibodies (mAbs), and large multimeric enzymes. These include interferon alpha 2b (IFN), human growth hormone (hGH), a Fab, and a mAb.
A Biolex publication states that IFN and hGH was successfully isolated from Lemna growth medium,
"At least 50% of IFN and hGH was secreted into asceptic growth media with pre-purification titers as high as 609 mg/L. Both proteins were found to be biologically active with IFN shown to be at least equal to the commercial source, Intron A. Efficient secretion of these recombinant proteins into an inorganic media with no need for viral inactivation offers substantial cost advantages in downstream purification."
It should be noted that Biolex defines "pre-purification titer" to include a 50x concentration step, so that their actual titer in Lemna medium would be 609/50 = 12 mg/L. Biolex indicates that it is working on optimization of protein secretion from duckweed cultures.
Another key advantage of recombinant Lemna cultures is that, unlike mammalian tissue culture systems, animal viruses cannot multiply. Therefore, this system should provide an increased level of pathogen safety in the final product. Currently many recombinant proteins are produced in mammalian cell cultures, where processes and tests to assure pathogen safety are major costs of production.
In the summer of 2003 Biolex announced substantial new
investments from venture capital sources.
In the spring of 2004 Biolex acquired Epicyte Pharmaceutical, Inc. a biotech company based in
John R. Gasdaska, David Spencer and Lynn Dickey "Advantages of Therapeutic Protein Production in the Aquatic Plant Lemna" BioProcessing Journal, Mar/Apr 2003.
Katharina Schoebi, "One weed you do not want to get rid of" Checkbiotech
Duckweeds Engineered for Bioremediation.
USDA scientists in Peoria, Illinois are developing ways to convert renewable agricultural resources into value-added products. Their research may also show how genetically modified duckweeds can improve waste-water processing systems. One object of this research is to develop a duckweed which produces cellulase, the enzyme that converts cellulose into simple sugars. By converting cellulose into sugars, agricultural wastes containing cellulose could be used to make many valuable products, including lactic acid, ethanol, and glycerol.
Patents for GM Duckweed Applications.
Much of the technology for genetic modification of duckweeds can be found in patent literature. These patents can be read on-line and have considerable information about this technology.
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- Arabidopsis is a small member of the Brassica family. It is the subject of a concentrated genome sequencing project, the Arabidopsis Genome Initiative (AGI). For more information, visit the Arabidopsis Information Resource (TAIR) and read "All about Arabidopsis" by Amy Fluet.
- Cytogenetics (cyto = cell + genetics) is the study of chromosomes using the microscope.
- Chromosomes are the small bodies in the cell that contain DNA. During cell division (mitosis), chromosomes condense from the nucleus and become discrete and compact. They can be identified and counted under the microscope only during mitosis and meiosis.
- GM (genetically-modified). Human beings have been modifying plant genes in many ways for centuries. For example, corn and wheat do not even exist in the wild. These domesticated plants and others are the product of thousands of years of human intervention. However, today, GM refers specifically to the precise modifications that are possible by the use of DNA technology.
- Genetic engineering is the use of DNA technology to genetically-modify organisms. This technology includes cloning (isolating) specific genes, copying, sequencing, editing, and splicing the isolated genes, and re-introducing the genes into other organisms to produce genetically-modified organisms. This technology is precise and controllable so that the results of each step are known. This is in contrast to conventional breeding, which results in a random assortment of the genes from the parents.
Background Information on Plant Genetic
Engineering
Techniques of Plant Molecular Biology
- Research
Tools for Plant Nucleic Acids: Isolating and manipulating the
plant genome by Christopher M. Smith, San Diego Supercomputer Center
(SDSC), published in The Scientist 14[22]:26,
Topics:
- Extraction, Purification, and Cloning of Plant Genomic DNA/RNA,
- Reporter Genes and Proteins, Gene Transfer,
- Gene Guns
- A Shot in the Dark: Invention of the Gene Gun. How a squirrel problem lead to a breakthrough in biotechnology.
Public Issues: GMO - Genetically Modified Organisms and Plant Agriculture
- Information Systems for Biotechnology (ISB) A national resource in agbiotech information from Virginia Tech.
"...provides information resources to support the environmentally
responsible use of agricultural biotechnology products. Here you will find
documents and searchable databases pertaining to the development, testing and
regulatory review of genetically modified plants, animals and microorganisms
within the U.S. and abroad. "
Topics include:
- Current News
- Regulatory Information
- Risk Assessment
- Research Resources
- Meetings
- Links
- Transgenic
Crops, An Introduction and Resource Guide,
from the Department of Crop and Soil Sciences,
Topics include:
- History of Plant Breeding,
- What are Transgenic Plants?
- How do you make Transgenic Plants?
- How to make Transgenic Plants: Animation Demo
- Evaluation & Regulation,
- Current Transgenic Products,
- Future Transgenic Products,
- Risks & Concerns,
- News Updates
- Agricultural Biotechnology Links from the American Society of Plant Biologists (ASPB), including the ASPB "Statement on Genetic Modification of Plants Using Biotechnology".
- Public Outreach information from the University of California slides and text from talks to farmers, scientists and the general public from UC Extension Specialists.
Topics Include:
- Consumer/Grower Issues
- Crop Specific Issues
- Environmental Biotechnology
- Intellectual Property
- Regulatory Issues
- What's in the Pipeline: Looking in the Crystal Ball at Agricultural Biotechnology
- AgBioWorld Foundation is devoted to bringing information about technological advances in agriculture to the developing world.
"AgBioWorld seeks to provide
information to scientists, policymakers, journalists and the general public on
the relevance of agricultural biotechnology to sustainable development."
AgBioWorld's President, Dr. C.S. Prakash, is also the Director of the Center
for Plant Biotechnology Research at
- AgBioView - a discussion group on agricultural biotechnology, features discussion of hot issues in GMO and agriculture.
- Benefits of Biotechnology for Developing Countries
- Response to the myths being circulated by anti-biotech activists.
- 31 Critical Questions in Agricultural Biotechnology from AgBioWorld
1. Questions About Food Security
2. Questions About Environmental Protection
3. Questions About Human Health
4. Questions About Socio-economic Issues
- Urban
Myths about Organic Agriculture. by Prof.
Tony Trewavas,
"There is a widespread belief that farming systems with lower yields and
lower use of inputs are more friendly to the
environment, and more sustainable than higher producing systems. Organic food
is often viewed as healthier and benign. However the information below rarely
finds its way into discussion on organic food but is essential for a critical
assessment."
- Agricultural Biotechnology and Genetically Engineered Foods - documents from various perspectives from the Food Safety Network.
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Revised: September 5, 2007