 |
July 1997 | |
NEWS FOR THE AGRICULTURAL AND ENVIRONMENTAL BIOTECHNOLOGY COMMUNITY
|
July 1997 | |
NEWS FOR THE AGRICULTURAL AND ENVIRONMENTAL BIOTECHNOLOGY COMMUNITY
In This Issue:
Public Meeting on EPA's Plant Pesticide Rule
Boom and Bust of Insect Resistant Bt Cotton?
Crops Engineered to Tolerate Aluminum Toxicity
CuraGen and Pioneer Hi-Bred Sign Major Deal
Significant objections have been raised by scientists who emphasize that all plants are able to prevent, destroy, repel or mitigate pests or diseases. A consortium of 11 scientific societies, whose members study plants, food, plant pests and diseases, and plant defense mechanisms, responded to EPA's regulatory initiative with a 35-page report entitled "Appropriate Oversight for Plants with Inherited Traits for Resistance to Pests". Opponents fear the EPA policy will erode public confidence in the safety of the food supply by sending the message that all plants contain pesticides. Furthermore, while the agency wants to expand its federal regulatory powers over the characteristics of plants that help plants resist diseases and pests, the proposed rule singles out for regulation only those pest-resistant qualities that were transferred to the plant through recombinant DNA technology.
The complete text of EPA's policy and proposed rule for plant- pesticides, and the response coordinated within the scientific community, may be found on the ISB website ( http://www.isb.vt.edu). With regard to the upcoming workshop, differing views as to what will transpire indicate that the controversy is not over.
The EPA View
The following text appeared as supplemental information in the Federal
Register announcement published June 13, 1997.
"As the development and commercialization of plant pesticides matures, the stakeholders involved in this industry need a better understanding of the issues facing the regulators and the regulated community. This understanding can serve to bring these potentially risk-reducing technologies to faster commercialization and use. Through a cooperative agreement with EPA, the National Foundation for Integrated Pest Management Education is sponsoring a workshop to bring EPA's regulators, the seed industry, researchers, plant pesticide registrants, and other interested stakeholders together to develop an understanding of the issues. This agreement was funded by President Clinton's Environmental Technology Initiative, which was designed to encourage public/private cooperation toward the goal of commercializing technologies whose use improves the environment. The conference will consist of formal presentations by EPA, the seed industry and researchers with panel discussions on issues of concern. The following topics will be covered: plant pesticide registration process; types of studies required for registration and possible exemptions; labeling requirements; seed research and commercialization process. Time will be allotted for questions and open discussion.
"This workshop will explore issues concerning the implementation of the EPA's proposed regulation of plant-pesticides and its impact on transgenic plant research and development, emphasizing so-called minor crops. Speakers from the public and private sector will describe how they develop and release new plant varieties, what lies ahead in transgenic strategies for pest and disease control, and how food and environmental safety risks can be effectively managed."
The Plant Scientists' View
The letter below is from Joyce A. Nettleton, Director of Science
Communications at the Institute of Food Technologists, which
coordinated the response from the consortium of scientific societies.
"The Environmental Protection Agency will convene a workshop on July 17 and 18 to discuss the Agency's proposed policy to regulate the inherited traits of plants as "plant-pesticides." The workshop is a consequence of a meeting held in December 1996 between representatives of the agency and scientific societies who have expressed concerns about the proposed policy, which has yet to be finalized.
"The EPA views the workshop as an opportunity to explain how it will regulate new plant varieties containing plant pesticides under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). Many plant scientists, however, intend to reiterate at the workshop their concern that the policy will stifle critical research using recombinant DNA technology on new plant varieties, especially for minor use crops. This and other scientific concerns with the policy are captured in the report, "Appropriate Oversight for Plants with Inherited Traits for Resistance to Pests," issued in July 1996 by a consortium of 11 professional, scientific societies.
"We expect this meeting to provide a forum for lively discussion of all aspects of this controversial issue and, therefore, urge you to attend. ... If you would like additional information or a copy of the consortium report, please give me a call. I may be reached at 312- 782-8424 or by email at janettleton@ift.org."
The (tentative) Agenda
The one and a half day workshop will be held July 17-18 at the
Doubletree Hotel, Arlington, VA (703-416-4100); it is open to the
public. The preliminary agenda includes:
Pat Traynor
Information Systems for Biotechnology
traynor@nbiap.biochem.vt.edu
A major worry lurking behind this success is the potential vulnerability of Bt crops to eventual adaptation by insect pests. Large scale deployment of Bt transgenics will certainly impose a selection pressure for pre-existing Bt-resistant insects to increase their numbers. As a result, the effectiveness of this environmentally sound method of pest control would be reduced. Although several resistance management strategies have been proposed to slow the evolution of insect adaptation to Bt genes, they are not based on empirical data, such as the initial frequency of resistance alleles in the population, but rely instead on theoretical estimates that may prove inadequate.
According to Bruce Tabashnik, University of Arizona, excitement over the success of Bt plants "must be tempered with an admission of ignorance" on how to effectively manage pest resistance to ensure long term durability of the approach. Thus a study conducted by a team led by Fred Gould of North Carolina State University may be a turning point in Bt research because it provides the first direct estimate of the field frequency of Bt-resistant insects (1). They report that in tobacco budworms (Heliothis virescens), a major cotton pest, 1 in 350 individuals carried an allele for resistance to the Bt toxin. This estimate is considerably higher than those assumed in earlier theoretical models, and thus forebodes a swift evolution of resistant insect populations. Tabashnik calls this study "a timely finding" which "provides inspiration to plunge ahead" into larger field tests of resistance management tactics (2).
The study was a mammoth effort that began with collecting 2,000 male insects from four cotton-growing states in 1993, before transgenic Bt crops were grown commercially. As the resistance trait is recessive, it is difficult to detect heterozygous insects but estimates of the number of such heterozygotes carrying recessive alleles are critical as those individuals are predominant in any population. The collected males were then individually crossed with females of a strain selected for its extreme high resistance to CryIA(c), the Bt gene used in cotton against tobacco budworm.
The resulting first and second generation progeny from 1025 successful crosses were tested for resistance to Bt toxin using artificial diets in the laboratory. Three males from the sample of 1025 were confirmed to be carrying an allele for resistance to Bt toxin, leading Gould and co-workers to conclude that field frequency of Bt resistance alleles was about 3 in 2,000. William Moar of Auburn University comments, "Gould's research definitely illustrates that resistance management procedures such as refuges, intense field monitoring of transgenic plants for potential escapes, and alternate control strategies are essential to maintain the viability of this valuable resource."
To slow the adaptation of insects to Bt cotton, the EPA has mandated that cotton growers should plant at least 4% of their crop with non-transgenic cotton and this refuge cannot be treated with any insecticides. The idea is that such 'refuges from toxin' will harbor susceptible insects and thus retard the evolution of insect resistance against the Bt gene. Gould et al. predict that with 4% refuge, the Bt cotton could remain efficacious to tobacco budworm for 10 years. This is not bad considering that insects have developed resistance to many pesticides and conventional varieties in less time than that. However, the current Bt cotton has less resistance to other pests such as cotton bollworm and European corn borer, and thus the authors predict a boom cycle of only 3-4 years for this variety. Again Tabashnik puts it elegantly -"Nothing will be gained and much can be lost if we pretend to know more about resistance management than we really do".
References
1. Gould, F. et al. 1997. Proc. Natl. Acad. Sci., USA 94:3519-3523
2. Tabashnik, B.E. 1997. Proc.Natl. Acad. Sci., USA 94:3488-3490.
(You can view or download the full text of papers published in PNAS at http://www.pnas.org)
C. S. Prakash
Center for Plant Biotechnology Research
Tuskegee University
prakash@acd.tusk.edu
CROPS ENGINEERED TO TOLERATE ALUMINUM TOXICITY
Aluminum is the most abundant metal on earth and has a
ubiquitous presence in the human environment in the form of
products such as beverage cans, kitchen utensils and aircraft.
However, aluminum (Al 3+) is very unfriendly to agriculture as it
injures plant root cells and thus interferes with root growth and
nutrient uptake in crops. Aluminum's harmful effects are
worst under acidic conditions where it becomes soluble; in non-
acid soils it is insoluble and thus less deleterious. More than
one-third of the arable land in the world suffers from soil
acidity and aluminum toxicity; low agricultural productivity in
acid soils is directly attributable to the effects of aluminum.
The problem is most severe in the humid tropics. In Colombia, for instance, 70% of the agricultural land is acidic. Crops such as corn, field bean, soybean and cotton thus do not grow well in the tropics because of their high sensitivity to soil acidity. Corn grown under acid soils can suffer yield losses up to 80%. Agricultural lime is applied by farmers around the world to combat the problem, but liming is a recurring financial burden on resource-poor farmers and also contributes to run-off pollution.
A recent report from a research team in Mexico led by Luis Herrera-Estrella may provide a breakthrough to the aluminum problem in agriculture (1). By introducing a bacterial citrate synthase (CSb) gene into tobacco and papaya, the Mexican scientists have genetically engineered plants that are more tolerant to the insidious metal.
The strategy capitalized on the fact that some plants tolerate aluminum by releasing citric acid which binds to the metal making it difficult to enter plant roots. Transgenic plants expressing the CSb gene from Pseudomonas aeruginosa produced up to ten-fold more citrate in their roots and released four-fold more of the compound than control plants. When grown under extremely high aluminum and acidic conditions, transgenic CSb plants showed substantially lower root growth inhibition compared to the untransformed plants. Normal seeds failed to develop roots when germinated in the presence of high aluminum while transgenic CSb seeds showed a clear tolerance. Transgenic roots contained less aluminum in their tissues, possibly because the citrate synthase produced by these plants was preventing uptake.
Herrera-Estrella, who was among the first to develop transgenic plants in the early eighties, has already introduced the citrate synthase gene into two more important crops, rice and corn (2). If these two crops, along with tobacco and papaya, prove to be tolerant to aluminum with no reduction in their yield or growth under field conditions, the research will likely have a major impact on agriculture in the tropics. Soils that were once inhospitable may now be brought under cultivation (2). The technology certainly appears to have the potential to elevate agricultural productivity in developing countries where the devastating effects of aluminum are at their worst, and where the need to produce more food is most urgent. This new report provides another illustration of how basic biotechnology research is being used ingeniously to address practical problems of the real world.
References
1. J.M. de la Fuente, et al. 1997. Aluminum tolerance in transgenic
plants by alteration of citrate synthesis. Science 276:1566-1568.
2. M. Barinaga, 1997. Making plants aluminum tolerant. Science 276:1497.
C. S. Prakash
Center for Plant Biotechnology Research
Tuskegee University
prakash@acd.tusk.edu
Pioneer's most recent deal is with CuraGen, a Connecticut based company. CuraGen combines gene identification technologies with software tools to accelerate the analysis and discovery of genes and the products of their expression. The deal was driven by the synergy created in bringing together CuraGen's genomic and bioinformatics capability with Pioneer's extensive germplasm base and knowledge of plant genetics and molecular biology (2).
Under the terms of CuraGen's first major agreement, Pioneer will make a $7.5 million equity investment and will fund $17.5 million in research over a five year period. Pioneer will have worldwide development and marketing rights for seed and agricultural products, while CuraGen will retain rights for human and animal health applications. Both companies will receive royalties on the sale of licensed products developed by the other (2). In addition, the two firms will collaborate on enhancing CuraGen's bioinformatics systems. CuraGen has developed a secure web-based operating system called GeneScape(TM). The system allows logical operations for genome-wide scans of gene expression and genomic differences, which can be used for genomics discovery. The system also includes Gene-Calling(TM) software which provides proprietary algorithms that convert DNA fragment patterns into names of genes (3).
"We stand at an inflection point in history," said Jonathon M. Rothberg, CuraGen's founder and CEO. "In much the same way that the development of plant hybrids contributed to the productivity of agriculture over the past 70 years, the discoveries we make in this collaboration will form the basis of agriculture for the next 70 years" (2). Investors seem to agree, as Pioneer's stock (NYSE: PHB) has climbed in the last year from a per share price in the low $50's to the mid-$70's (4). This collaboration can also only buoy CuraGen's outlook for a prosperous future initial public offering.
References
1. Strickland, D., CuraGen Takes Genomics Know-How To The Table
For $25M Deal In Ag Research. BioWorld Today, Volume 8, No.
124, June 27, 1997, pp. 1,6.
2. CuraGen and Pioneer Hi-Bred sign largest agronomics deal ever. CuraGen Press Release, June 24, 1997, CuraGen WWW site (http://www.curagen.com).
3.CuraGen website (http://www.curagen.com).
4.StockMaster website (http://www.stockmaster.com).
William O. Bullock
Institute for Biotechnology Information
http://www.biotechinfo.com
The material in this News Report is compiled by NBIAP's Information Systems for Biotechnology, a joint project of USDA/CSREES and the Virginia Polytechnic Institute and State University. It does not necessarily reflect the views of the U.S. Department of Agriculture or of Virginia Tech. The News Report may be freely photocopied or otherwise distributed without charge. P.L. Traynor, Editor.
Information Systems for Biotechnology, 120 Engel Hall, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061-0308, tel: 540-231-2620, fax: 540-231-2614, email: traynor@nbiap.biochem.vt.edu
For internet access to the News Report, textfiles, and databases use one of the following procedures.
1. Through WWW: http://www.isb.vt.edu/
2. To have the News Report automatically emailed, send an email message to news@nbiap.biochem.vt.edu and type subscribe newsreport [your-name] in the message section.
ISB News Report
120 Engel Hall
Virginia Tech
Blacksburg, VA 24061-0308