[escepticos] Plantas transgénicas para detectar explosivos

[Josep Catala <jcatala@...>]

Envio a la corrala un mensaje recien recibido. Para mi al menos, es de
gran importancia.

Saludos pacíficos.

Josep Català
________________Transgénicos contra explosivos______________

> Adjunto un artículo publicado en ISB por Sarah K. Wheaton
> de la Universidad de Rhode Island, donde describe la utilización de
> plantas OMG para detectar minas y otras utilidades como biosensores.
>
> Es sólo un ejemplo de las inmensas posibilidades de esta tecnología y
> de las puertas que se pretenden poner a la imaginación demonizando a
> estas técnicas.
>
>
> PLANTS THAT DETECT LANDMINES, AND OTHER BIOSENSORS
>
> The furor over genetically modified (GM) plants has focused on crops with
> engineered agronomic qualities, such as insect resistance and herbicide
> tolerance. Critics are primarily concerned with food safety issues and
> ecological consequences. But GM technologies have much further ranging
> applications than simply agriculture. While their potential for improving
> crops plants is important, environmental monitoring is an area where GM
> plants can perform a crucial role in a low-impact manner, a role that even
> GM opposition would be hard-pressed to criticize.
>
> It is possible that in the near future, GM plants could provide constant,
> landscape-level data on environmental hazards. Current monitoring of
> surface and sub-surface contaminants, both inorganics such as heavy
> metals and organic toxins such as PCBs, relies on frequent water sampling
> of wells, an expensive and labor-intensive task. GM plants could be used as
> biosensors to monitor radioisotope levels around nuclear power plants, or
> to detect jet fuel contaminants at military bases. They could also disclose
> the presence of certain other unwanted and especially dangerous
> substances in our environment of which presently there is no good way of
> monitoring. One of these is buried explosive devices.
>
> Several laboratories are currently performing research using plants as
> biosensors. This entails the isolation of specific inducible promoters (gene
> switches) that can be fused to one or more genes encoding a visible
> marker. The current visible marker of choice is green fluorescent protein
> (GFP) from the Pacific jellyfish (Aequorea victoria). GFP has the unique
> property of fluorescing green when excited by blue or UV light. A DNA
> construct containing a specific inducible promoter could be fused to GFP
> and then transferred into a plant for biomonitoring. For example, in a case
> where the promoter has been isolated and modified so that it is responsive
> to copper(1), plants containing this construct might be deployed around the
> periphery of a copper mine to monitor copper movement into the
> surrounding countryside. When copper was present in sufficient
> concentrations to trip the promoter, plants would fluoresce green at that
> location. Ultimately biosensors of nature could be used in conjunction with
> bioremediators, the perfect marriage being that where an individual plant
> performs both functions.
>
> The application we want to consider here is the detection of buried
> explosive devices, such as landmines. Landmines generally have small
> plastic housings of extremely inexpensive construction that contain
> trinitrotoluene (TNT) or other explosives. Landmines come in various sizes
> and shapes and are, for the most part, designed to explode and maim
> whatever steps on the soil surface covering the mine. Cambodia, Angola,
> and Pakistan are examples of countries that are littered with landmines
> deployed by invading military, government, and/or rebel groups. Most of the
> nations in this situation are those whose economies rely heavily on
> non-automated agricultural production, and the presence of landmines
> effectively removes large areas of arable land from agricultural production.
> The more obvious and urgent problem is that these mines kill and maim
> multiple people everyday. Those who live in the vicinity of minefields are
> normally aware of the existence of the minefield itself, but not of the
> specific
> locations of the mines that may be planted randomly as little as 10 meters
> apart. Since they are plastic, landmines cannot be located by metal
> detectors; in the developing world, the most common de-mining practice is
> that of a man with a stick. He will search for a landmine by feel, a
> practice
> that is imprecise at best and often a hideous short-term career at its
> worst.
>
> The idea to use organisms to detect TNT was first exemplified using GM
> bacteria by Dr. Robert Burlage and his coworkers at the Oak Ridge National
> Laboratory(2). Their bacteria, Pseudomonas putida, had a TNT inducible
> promoter fused to GFP and were tested on a faux minefield with surrogate
> landmines. Pseudomonas putida detected five of five landmines in a
> one-quarter acre plot; however, they also produced two false positive
> signals, indicating the presence of a landmine where none existed. There
> are several other drawbacks to a bacterial-based system. It requires that
> bacteria be grown and sprayed onto the minefield, which could be
> determined to be environmentally unacceptable. A government also might
> well object to the release of recombinant bacteria in the interest of
> national
> security. Additionally, it has been found that the bacterial signal is
> dependent on a plant substrate for bacterial colonization. A plant-based
> detection system has the advantage of utilizing a macroscopic, and
> trackable, organism; TNT would be absorbed by plant roots and then
> transported to leaves(3) where the fluorescence could be readily observed.
> The root structures would also more effectively mine the soil for trace
> explosive, resulting in increased mapping accuracy. Another advantage is
> that the plants used could be optimized for specific ecological conditions.
>
> How would such a plant-based TNT detection system work? The first step
> would be sowing detector plant seed over a minefield in a manner that
> would result in uniform coverage, a potential logistical problem that would
> require helicopter-based seed pelleting. A homogeneous stand of plants
> would need to be established so the roots could cover the mine-leachate
> soil volume. It would be necessary to supply plants with water and nutrients
> via a helicopter to assure they will be in good health with normal protein
> production. Finally, plants would need to be detected. Simply, the plants
> located over a landmine would fluoresce green; those not in the proximity of
> a mine would not fluoresce. The false positive signals in the bacterial
> system were due to leaching(2); a plant-based system, where the promoter is
> tripped by an accumulation of TNT, should not be nearly as vulnerable.
>
> An important component of any detection system is the photonic device
> used for picking-up the fluorescent biosensor signals. At our laboratory in
> North Carolina, we work at ground level in the dark using a strong UV lamp
> to shine on GFP-producing plants. Obviously, this practice is not
> transferable to a field situation where it becomes far too reminiscent of
> the
> man with the stick. In another National Laboratory in Santa Barbara, John Di
> Benedetto and his colleagues have produced laser-induced fluorescence
> imaging (LIFI) and laser-induced fluorescent spectroscopy (LIFS) devices
> that can be used to detect and measure fluorescence from a stand-off(4).
> Scaling remote sensing to airborne devices is critical for the successful
> detection of biological-based landmine detection systems and other
> real-time biosensors. Says Dr. Di Benedetto, "(Airborne) laser-induced
> fluorescence will provide remote access and direct evidence of specific
> contamination, whether it is TNT, heavy metals, or pathogens. It will bring
> a
> whole new dimension to remote sensing."
>
> The uses of biotechnology will increasingly move from the agricultural and
> medical toward environmental applications. A number of research groups in
> both the public and private sectors are working to make environmentally
> useful GM organisms a reality. We believe the wholesale environmental
> objection to GM plants will be moderated by landmine-detecting GM plants,
> as well as other explicitly environmentally useful GM plants. A
> biotechnology
> that can monitor the presence of environmental contaminants, and then
> possibly even clean them up, has the potential to replace expensive extant
> technologies. For example, plants that can bioremediate mercury have
> already been developed(5). These plants have the ability to absorb and
> convert toxic forms of mercury to less-toxic elemental mercury that they
> subsequently volatilize, and a mercury-inducible GFP marker would be a
> useful addition. Biotechnology can and should play a pivotal role in
> monitoring toxins and in cleaning up the environment. A GM plant that
> detects the location of landmines seems like a biotechnological advance
> that even Prince Charles could love.
>
> Sources:
> 1. Mett VL, Lochhead LP, and Reynolds PHS. 1993. Copper-controllable
> gene expression system for whole plants. Proceedings of the National
> Academy of Sciences USA 90(10): 4567-4571.
>
> 2. Burlage RS. 1999. Green fluorescent bacteria for the detection of
> landmines in a minefield. Abstracts of the Second International Symposium
> on GFP, San Diego, CA.
>
> 3. French CE, et al. 1999. Biodegradation of explosives by transgenic
> plants expressing pentaerythritol tetranitrate reductase. Nature
> Biotechnology 17(5): 491-494.
>
> 4. Di Benedetto J. 1999. Laser-induced fluorescence remote sensing.
> Abstracts of the Second International Symposium on GFP, San Diego, CA.
>
> 5. Bizily SP, Rugh CL, and Meagher RB. 2000. Phytodetoxifica-tion of
> hazardous organomercurials by genetically engineered plants. Nature
> Biotechnology 18(2): 213-217.
>
> C. Neal Stewart, Jr.
> University of North Carolina at Greensboro and
> Transgreenix Corporation
> nstewart en uncg.edu
>
> Sarah K. Wheaton
> University of Rhode Island