GENETICALLY MODIFIED CROPS OR TRANSGENIC PLANTS /CROPS
The most important use of the plants biotechnology is the production of superior transgenic crops/plants which are having not only the resistance against a variety of biotic and abiotic stresses, but also having some improved value added properties like nutritional quality of food.Transgenic plants are those plants in which a foreign gene has been introduced and stably integrated into host DNA. A gene that has transferred using the tools of molecular biology is called transgene. The.The transfer or introduction of a foreign gene result in synthesis of desirable traits like disease resistance, insect resistance, herbicide resistance, etc.
Transgenic plants have now been produced in more than 60 plants species (mostly in dicotyledonous families and in some monocotyledonous families also).The first transgenic plants were produced in tobacco (Nicotiana tobacum).Some other higher plants where transgenic plants have been produced are petunia hybrid,Lycopersicum esculentum (tomato), solanum tuberosum (solanum) melongena (brinjal), Lactuca sativa (lettuca) ,Brassica napus (oilseed rape or canola), Glycine max (soybean), piscum sativum (pea), Beta vulgaris (sugar beet), vitis vinifera (grape),Asparagus. Secale cereale (rye), Triticum aestivum (wheat), Zea mays (maize), Avena sativa (oat) and a gymnosperm picea glaucoma (white spruce), etc.
Some of the transgenic plants have been released for commercial cultivation,e.g.,'Flavr savr' and Endless Summer' tomatoes, 'Freedom II' Squash, 'high lauric' rape and seed or canola, 'Roundup Ready' soybean. Similarly genetically engineered insect resistance potato (New leaf ), corn (Maximizer) and cotton (Boll gard), each having Bt toxin gene from B acillus thuringiensis, have been granted full registration. Transgenic plants/crops are also called genetically engineered crops or gm crops (genetically modified crops) or gmo (genetically modified organised)
Salt tolerant transgenic plants have been developed in Arabidopsis and tomato and heribicide resistance transgenic plants have been developed in maize, beet, rape, tomato, potato, tobacco, chicory and melon.
Specific gene transfer in plants is mostly done with Agrobacterium tumefaciens bacteria (causes crown gall) diseases in many dicots). The tumour causing ability resides in a plasmid called Ti plasmid of a tumefaciens. This plasmid has become important in plant breeding because specific genes can be inserted into the Ti plasmid by recombinant DNA technique and thereby changing the genotype and phenotype of the plant. A tumefaciens based gene transfer is hampered by host range limitations.
Nematode resistance in tobacco plants has been brought about by RNA interference( RNAi) technique. In the technique, a complementary RNA binds to mRNA to form a dsRNA, which is unable to translate and hence the expression is blocked. Here a nematode specific gene is introduced in host plant. When this plant is infected by the nematode, the nematode specific gene is triggered and it produced a single stranded RNA which is complementary to RNA produced by the nematode is order to infect the host plant. This complementary RNA binds to the mRNA of the nematode to form a double stranded RNA that cannot be translated. Hence the nematode is unable to infect the transgenic tobacco plant.
Gene transfer can also be made directly without using biological vectors (plasmids, bacteriophages, etc.) Naked plant cells as protoplasts have been found ideal for vectorless gene transfer. Some vectorless gene transfer methods are:
a)Gene transfer using practicle bombardment or biolistics which involves directly shooting a piece of DNA into the recipient plants tissue by a gene gun. Tungsten or gold beads (which are smaller than the plants cells themselves) are coated in the gene of interest and fired through a stopping screen, accelerated by Helium, into the plants tissue. The particles pass through plant cell, leaving the DNA inside. This technique is being used in monocotyledonous and dicotyledonous plants successfully. It is relatively simple laboratory technique. The transformed tissue is selected using marker genes such as those that code for antibiotic resistance. Whole plants are then regenerated from the totipotent transformed cells in culture, containing a copy of transgene in every single cell.
b)technique
c)Macroinjection
d)Lipofection
e)Silicon carbide fibre-vortex
f)Ca-DNA co-precipitation method
g)Electroporation
h)Ultrasonication
i)UV-laser microbeam ( However, success in few systems).
Recently , transgenic plants have been explored for production of biologically active peptides and proteins (having pharmaceutical applications including use as vaccines immunomodulators , growth factors, hormones, blood proteins and enzymes).These proteins and peptides play a key role in production of edible vaccines and antibodies , which are convenient and inexpensive for immunotherapy. An edible vaccine against diarrhoea has been expressed in potato and against dental caries in tobacco. Research on transgenic plant-based production of various vaccines and antibodies is in early stages but these generate a hope towards low-cost edible vaccines and antibodies from plants.
Plant bio technologies in india have claimed the production of an edible vaccine against cholera in tomato. This tomato will be light bluish in colour and is expected to be in market in next years.
Golden rice or Miracle rice (rich in vitamin A or b-carotene and iron ) and decaffeinated coffee are also valuable achievements of gene transfer technology.
Biosafety of Transgenic plants: Nowadays, there is a debate on biosafety issues of transgenic plants. The key points are:
i. Potential of GM crops to become weeds.
ii. Opportunities of gene flow from a GM plant to other plant.
iii. Impact of growing transgenic plants on biodiversity.
iv. Capacity of pest and pathogens to adapt to the cultivation of GM crops.
Ignoring the risks involved in cultivation of transgenic crops, in China, 2300 hectares of land has been placed under transgenic crops . In india, however onlyone transgenic crop (bt-cotton) has so far been released for cultivation. Some srains of Bacillus thuringiensis produce proteins which have the property of killing certain insects. Specific by toxins genes isolated from Bacillus thuringiensis are incorporated into cotton and other crop plants. As most of the bt toxins are insect-group specific, so choice of genes depends upon the crop and the targeted pest. The bt toxin is coded by a gene called cry, Which are of different types like cry 1Ac, cry II Ab (Controlling cotton bollworms) and cry 1Ab (controlling corn borers). Recently in March 2002, Government of India has permitted the commercial cultivation of three varieties of bt-cooton, the first genetically modified crop of the country. This has been developed by MAHYCO ( Maharashtra Hybrid Seeds Company ) in collaboration with American company Monsanto. bt-cotton is resistant to Boll-worm disease of cotton.
The most important use of the plants biotechnology is the production of superior transgenic crops/plants which are having not only the resistance against a variety of biotic and abiotic stresses, but also having some improved value added properties like nutritional quality of food.Transgenic plants are those plants in which a foreign gene has been introduced and stably integrated into host DNA. A gene that has transferred using the tools of molecular biology is called transgene. The.The transfer or introduction of a foreign gene result in synthesis of desirable traits like disease resistance, insect resistance, herbicide resistance, etc.
Transgenic plants have now been produced in more than 60 plants species (mostly in dicotyledonous families and in some monocotyledonous families also).The first transgenic plants were produced in tobacco (Nicotiana tobacum).Some other higher plants where transgenic plants have been produced are petunia hybrid,Lycopersicum esculentum (tomato), solanum tuberosum (solanum) melongena (brinjal), Lactuca sativa (lettuca) ,Brassica napus (oilseed rape or canola), Glycine max (soybean), piscum sativum (pea), Beta vulgaris (sugar beet), vitis vinifera (grape),Asparagus. Secale cereale (rye), Triticum aestivum (wheat), Zea mays (maize), Avena sativa (oat) and a gymnosperm picea glaucoma (white spruce), etc.
Some of the transgenic plants have been released for commercial cultivation,e.g.,'Flavr savr' and Endless Summer' tomatoes, 'Freedom II' Squash, 'high lauric' rape and seed or canola, 'Roundup Ready' soybean. Similarly genetically engineered insect resistance potato (New leaf ), corn (Maximizer) and cotton (Boll gard), each having Bt toxin gene from B acillus thuringiensis, have been granted full registration. Transgenic plants/crops are also called genetically engineered crops or gm crops (genetically modified crops) or gmo (genetically modified organised)
Salt tolerant transgenic plants have been developed in Arabidopsis and tomato and heribicide resistance transgenic plants have been developed in maize, beet, rape, tomato, potato, tobacco, chicory and melon.
Specific gene transfer in plants is mostly done with Agrobacterium tumefaciens bacteria (causes crown gall) diseases in many dicots). The tumour causing ability resides in a plasmid called Ti plasmid of a tumefaciens. This plasmid has become important in plant breeding because specific genes can be inserted into the Ti plasmid by recombinant DNA technique and thereby changing the genotype and phenotype of the plant. A tumefaciens based gene transfer is hampered by host range limitations.
Nematode resistance in tobacco plants has been brought about by RNA interference( RNAi) technique. In the technique, a complementary RNA binds to mRNA to form a dsRNA, which is unable to translate and hence the expression is blocked. Here a nematode specific gene is introduced in host plant. When this plant is infected by the nematode, the nematode specific gene is triggered and it produced a single stranded RNA which is complementary to RNA produced by the nematode is order to infect the host plant. This complementary RNA binds to the mRNA of the nematode to form a double stranded RNA that cannot be translated. Hence the nematode is unable to infect the transgenic tobacco plant.
Gene transfer can also be made directly without using biological vectors (plasmids, bacteriophages, etc.) Naked plant cells as protoplasts have been found ideal for vectorless gene transfer. Some vectorless gene transfer methods are:
a)Gene transfer using practicle bombardment or biolistics which involves directly shooting a piece of DNA into the recipient plants tissue by a gene gun. Tungsten or gold beads (which are smaller than the plants cells themselves) are coated in the gene of interest and fired through a stopping screen, accelerated by Helium, into the plants tissue. The particles pass through plant cell, leaving the DNA inside. This technique is being used in monocotyledonous and dicotyledonous plants successfully. It is relatively simple laboratory technique. The transformed tissue is selected using marker genes such as those that code for antibiotic resistance. Whole plants are then regenerated from the totipotent transformed cells in culture, containing a copy of transgene in every single cell.
b)technique
c)Macroinjection
d)Lipofection
e)Silicon carbide fibre-vortex
f)Ca-DNA co-precipitation method
g)Electroporation
h)Ultrasonication
i)UV-laser microbeam ( However, success in few systems).
Recently , transgenic plants have been explored for production of biologically active peptides and proteins (having pharmaceutical applications including use as vaccines immunomodulators , growth factors, hormones, blood proteins and enzymes).These proteins and peptides play a key role in production of edible vaccines and antibodies , which are convenient and inexpensive for immunotherapy. An edible vaccine against diarrhoea has been expressed in potato and against dental caries in tobacco. Research on transgenic plant-based production of various vaccines and antibodies is in early stages but these generate a hope towards low-cost edible vaccines and antibodies from plants.
Plant bio technologies in india have claimed the production of an edible vaccine against cholera in tomato. This tomato will be light bluish in colour and is expected to be in market in next years.
Golden rice or Miracle rice (rich in vitamin A or b-carotene and iron ) and decaffeinated coffee are also valuable achievements of gene transfer technology.
Biosafety of Transgenic plants: Nowadays, there is a debate on biosafety issues of transgenic plants. The key points are:
i. Potential of GM crops to become weeds.
ii. Opportunities of gene flow from a GM plant to other plant.
iii. Impact of growing transgenic plants on biodiversity.
iv. Capacity of pest and pathogens to adapt to the cultivation of GM crops.
Ignoring the risks involved in cultivation of transgenic crops, in China, 2300 hectares of land has been placed under transgenic crops . In india, however onlyone transgenic crop (bt-cotton) has so far been released for cultivation. Some srains of Bacillus thuringiensis produce proteins which have the property of killing certain insects. Specific by toxins genes isolated from Bacillus thuringiensis are incorporated into cotton and other crop plants. As most of the bt toxins are insect-group specific, so choice of genes depends upon the crop and the targeted pest. The bt toxin is coded by a gene called cry, Which are of different types like cry 1Ac, cry II Ab (Controlling cotton bollworms) and cry 1Ab (controlling corn borers). Recently in March 2002, Government of India has permitted the commercial cultivation of three varieties of bt-cooton, the first genetically modified crop of the country. This has been developed by MAHYCO ( Maharashtra Hybrid Seeds Company ) in collaboration with American company Monsanto. bt-cotton is resistant to Boll-worm disease of cotton.
Haim Toledano
ReplyDeleteCompletely agree with author... Biotechnology make a drastic change in production and quality in the field of agriculture. Thanks for sharing.