Transgenic Plants: New Vistas in Combating Environmental Pollution
Environmental pollution is serious concern for human civilization
. Increasing population pressure, industrialization, urbanization and deforestation is creating havoc for environment. Pollution level of soil, water and air is increasing day by day. Pollution can be controlled by checking their source, or by removing the pollutants from one place and dumping them at another place (common strategy followed for disposing solid wastes). Many strategies have been designed based on science , economics and politics to efficiently clean the pollutants. The traditional cleaning processes are labour intensive, time taking, expensive and are themselves very messy. Mere cleaning or removing the pollutants from one place is not at all a solution to combat pollution. Elimination of toxic waste and pollutant is the only solution. Bioremediation could change this scenario of waste treatment. "Bioremediation" means using living organisms to do a cleanup job. It can also eliminate the need of expensive and labour intensive process like digging, chemical treatments, incineration and land filling. Using bioremediation we can actually eliminate the solid wastes rather than mobilizing them from one place to another.
Bioremediation was first noticed about 10 years ago when more than 11 million gallons of crude oil spilled into water from a tanker; the spill was cleaned by using genetically engineered bacteria, which "eats" the oil. It is well known that plants and microbes can break down chemicals and petroleum into harmless products, breaking down of metals is far more difficult and is rarely done. Rather, with metals the effort is usually to "bind" or "immobilize" or "sequester" these so that if they are in water they remain accumulated in one place and not leach throughout the ecosystem. If the immobilizing plants or micro-organisms are on land, they collect the metals so that they can be carted off or sometimes released through the leaves in harmless forms and amounts.
According to the agronomists of the Department of Agriculture, the estimated cost of using plants to clean polluted soils could be "less than one-tenth the price tag for either raging up (scraping or digging) and trucking the soil to a hazardous waste landfill or making it into concrete" "Phytoremediation" takes advantage of the needs of certain plants including trees, grasses and aquatic plants to remove, destroy or sequester hazardous substances from the environment. The most common types of phytoremediation are rhizifiltration (uptake of toxins through roots), rhizoextraction (taking and storing contaminants in roots), phytotransformation (degradation of toxins through metabolism), phytostimulation (plants stimulating bacteria or fungi to degrade pollutants), phytostabilization (reducing the mobility of pollutants), phytovolatilization (uptake and transpiration of volatile compounds by plants). Certain plant species are called hyperaccumulators. They "have the ability to extract elements from soil and concentrate them in easily harvested plant stem, leaves and shoots".
Currently, there is little bioremediation making use of transgenic plants, in part because it is relatively new area and in part, unfortunately, because of antitransgenic activists efforts. But, its future lies with the transgenics. In their normal state, the plants may process pollutants too slowly for our needs. But in what is one of many cases of bioengineering piggybacking on other bioengineering, these plants are genetically induced not only to grow faster than normal but also to consume waste more quickly as well. Transgenic crops can directly or indirectly be useful in combating the problem of pollution. For direct use, plants can be transformed to increase their ability of phytoremediation. Indirectly, use of transgenic crops can reduce the need of harmful chemicals in agriculture, thus cutting off the source of pollution.
Researchers have inserted a gene from mammalian liver enzyme into the tobacco plant. The enzyme successfully breaks down a variety of toxic chemicals, chlorinated solvents. These transgenic tobacco plants are extremely fast at absorbing toxins such as TCE (trichloroethylene), dibromide, carbon tetrachloride, venyl chloride and chloroform. They are as much as 640 times faster than normal tobacco plants. The plants take the pollutants and degrade them completely.
Richard Meagher from the University of Georgia, Athens, is coaxing Arabidopsis plants into cleaning up dangerous mercury from hazardous waste sites. The dumped mercury is converted into methyl mercury by the microbes. Methyl mercury gets accumulated in the food chain to the levels (biomagnifications) that could cause severe neurological problems. Meagher isolated a bacterial enzyme, called mercuric ion reductase, that converts the metal ion into its less toxic forms, and placed this gene into Arabidopsis. The transformed plants grew well in the mercury contaminated soil and released mercury in to the air in harmless form (Phytovolatilization). Methyl mercury never got a chance to form. To increase the cleanup efficiency, Meagher gave the plants a shorter life span, so it can be grown and harvested six or seven times a year, and he gave it more height so that it can absorb considerably more mercury during each of those lifespans. The amount of mercury that the transformed plants converted was 10 nanograms per milligram of plant tissue per minute by weight of the plant tissue. Richard Meagher also had a trick to tackle the problem of arsenic contamination. His team of researchers in the University of Georgia inserted two unrelated genes of E. coli into Arabidopsis, allowing it to remove arsenic from the soil and transport it to the plant's leaves. The transgenic plants accumulated seventeen times as much fresh weight and thrice as much arsenic per gram of plant tissue as nontransgenic plants. Many metal transporter gene families have been identified which could be incorporated in plants lacking them to increase the ability to accumulate the metal ions from polluted soil or water (Hyperaccumulation). These gene families are prominent in the genomes of different species of genus Aspergillus (a fungus).
Table 1.Gene family responsible for reducing metal toxicity
Metal Gene family
Zinc ZIP
Niclel/Cobalt NiCoT
Manganese Nramp
ChromiumCHR
Arsenite ArsAB, ACR3
CopperCtr2, P-ATPase
Iron FeT, IRT
CationCDF
Heavy metal ABC, P-ATPase
Source: Transport database (www.tcdb.org)
A large source of pollution in most of the developing and underdeveloped countries is in the agriculture sector. Lot of pollution is caused by the harmful compounds, used as pesticides and weedicides. Many transgenic crops like BT-cotton are now being produced which doesn't require harmful pesticide sprays thus preventing the environment from being polluted by the harmful chemicals, which can cause severe disorders and even lethality to several fauna and even human beings by the processes like bioaccumulation and biomagnification. Use of insect resistant sweet corn in Florida has reduced the use of pesticide to 112,000 lbs/year (79%). Use of virus resistant raspberry in Oregon and Washington has decreased pesticide use to 371,000 lbs/year (50%). Insect resistant cotton in U.S. has reduced the use of pesticides to 2.7 million lbs/year. Herbicide resistant tomato in California has reduced the use of weedicides to 88,000 lbs/year (88%).
Table 2. Reduction in use of pesticide and weedicide due to use of transgenic crops
Crop---Reduction in pesticide and weedicide use---Production increase per year
Herbicide-resistant Tomatoes in California ---88,000 lbs./yr. (88%)---$10.7 million
Insect-resistant Sweet corn in Florida---112,000 lbs./yr. (79%)---$1.3 million
Virus-resistant Raspberry in Oregon / Washington---371,000 lbs./yr. (50%)---$2.5 million
Insect-resistant Cotton in U.S.*---2.7 million lbs./yr.---$99 million
(Source: National Center for Food and Agriculture Policy, Washington, DC)
Environmental pollution is increasing rapidly and it must be regulated and eliminated at a pace faster than the rate of increase of pollution to secure healthy life to the flora and fauna of the planet Earth. Transgenic crops with improved traits of absorbing more and more harmful chemicals and metal ions from the environment can be of great help in increasing the rate of elimination of pollutants thus, rescuing the environment from pollutants. Knowledge of metal ion transporter gene families can be used to make transgenic plants with ability to clean harmful metal ions from the environment. Use of weed and pest resistant transgenic varieties of crop plants can decrease the use of pesticides and weedicides and thus indirectly be helpful in combating environmental pollution.
Transgenic Plants: New Vistas in Combating Environmental Pollution
By: Shubhendu Seal
It Support Pasadena Enable Telnet In Windows Pasadena It Support Get To Know The Best Methods For Sport Utility And Light Truck Repair Sweet Budget Tips For Credit Repair Slow Windows Laptop - How To Speed Up A Slow Windows Laptop Easily And Quickly? Kodak Converter, Convert Kodak Video Off Kodak Zi8, Playsport Cameras On Windows How To Convert Kodak Video To Mp4/avi/3gp/flv/wmv/mkv On Windows What Should You Do When The Upgrade Of Windows Xp Makes The System Inaccessible Scaffold Towers Help Work Best for Roof Repairs Mcts: Windows Vista How To Easily Open New Windows In Windows 7 How To Activate Windows 7 Operating System On Your Computer? Vital Facts About Miami Pc Repair Services Easy DIY Decorating - Repairing Peeling Paint Spots