29 May 2011

TRANSGENIC PLANTS AS BIOREACTORS (MOLECULAR FARMING)


Improvement of seed protein quality

The nutritional quality of cereals and legumes has been improved by using biotechnological methods. Two genetic engineering approaches bear been used to recover the seed protein quality. Hip the principal pencil case, a transgene (e.G. Gene in lieu of protein containing sulphur rich amino acids) was introduced into pea conceal (which is deficient in methionine and cysteine, but rich in lysine) under the control of seed-specific promoter. Hip the minute approximate, the endogenous genes are modified so as to multiplication the essential amino acids like lysine in the seed proteins of cereals.
These transgenic routes bear helped to recover the essential amino acids contents in the seed storeroom proteins of a run to of crop plants. E.G. Overproduction of lysine by de-regulation. The four essential amino acids namely lysine, methionine, threonine, and isoleucine are produced from a non-essential amino acid aspartic acid. The formation of lysine is regulated by feed back inhibition of the enzymes aspartokinase (AK) and dihydrodipicolinate synthase (DHDPS). The lysine feedback- insensitive genes encoding the enzymes AK and DHDPS bear been in that order isolated from E. Coli and Cornynebacterium. After responsibility appropriate genetic manipulations, these genes were introduced into soybean and canola plants. The transgenic plants so produced had excessive quantities of lysine.

Diagnostic and curative proteins

Experiments are obtainable on to habit transgenic plants in diagnostics in lieu of detecting person diseases and therapeutics in lieu of curing person and subconscious diseases. Several metabolites and compounds are already being produced in transgenic plants e.G. The monoclonal antibodies, blood plasma proteins, peptide hormones, cytokinins and the like. The habit of plants in lieu of mercantile production of antibodies, referred to as plantbodies, is a novel approximate in biotechnology. The principal lucrative production of a functional antibody, namely a mouse immunoglobulin IgGI in plants, was reported in 1989. This was achieved by emergent two transgenic tobacco plants-one synthesizing extreme shackle gamma- shackle and other light kappa- shackle, and crossing them to generate descendants to facilitate can deliver an assembled functional antibody. Hip 1992, C.J. Amtzen and co-workers articulated hepatitis B shallow antigen in tobacco to deliver immunologically operational ingredients via genetic engineering of plants.
Several other curative proteins bear moreover been produced like haemoglobin and erythropoietin in tobacco plants, lactoferrin in potato, trypsin inhivitor in maize and the like. The principal proteins/enzymes to facilitate were produced in transgenic plants (maize) are avidin and beta-glucuronidase and are used in diagnostic kits.

Edible vaccines

Crop plants offer cost-effective bioreactors to express antigens which can be used as edible vaccines. The approximate is to cut off genes encoding antigenic proteins from the pathogens and at that moment expressing them in plants. Such transgenic plants or their tissues producing antigens can be eaten in lieu of vaccination/immunization (edible vaccines). The articulation of such antigenic proteins in crops like banana and tomato are worthwhile in lieu of inoculation of humans since banana and tomato fruits can be eaten red.
Transgenic plants (tomato, potato) bear been urbanized in lieu of expressing antigens derived from subconscious viruses e.G. Rabies virus, herpes virus. Hip 1990, the principal bang of the production of edible vaccine (a shallow protein from Streptococcus) in tobacco on 0.02% of come to leaf protein level was available in the form of a patent effort under the International Patent Cooperation Treaty (Mason and Arntzen,1995).The principal clinical trials in humans, using a conceal derived vaccine were conducted in 1997 and were met with imperfect star. This involved the eating of transgenic potatoes with a toxin of E. Coli causing diarrhea.

The process of making of edible vaccines involves the merger of a plasmid moving the antigen gene and an antibiotic resistance gene, into the bacterial cells e.G. Agrobacterium tumefaciens. The small pieces of potato leaves are exposed to an antibiotic which can murder the cells to facilitate lack the spanking genes. The surviving cells with altered genes multiply and form a corn. This corn is acceptable to grow and subsequently transferred to soil to form a complete conceal. Hip on the order of a only some weeks, the plants bear potatoes with antigen vaccines.

The bacteria E.Coli, V. Cholerae cause acute watery diarrhea by colonizing the small intestine and by producing toxins. Chloera toxin (CT) is very related to E.Coli toxin. The CT has two subunits, A and B. Attempt was made to deliver edible vaccine by expressing high temperature labile enterotoxin (CT-B) in tobacco and potato.

Another strategy adopted to deliver a plant-based vaccine, is to infect the plants with recombinant virus moving the desired antigen to facilitate is complex to viral coat protein. The infected plants are reported to deliver the desired fusion protein in portly amounts in a unfriendly duration. The procedure involves either insertion the gene downstream a subgenomic promoter, or fusing the gene with capsid protein to facilitate coats the virus.

Advantages of edible vaccines

The edible vaccines produced in transgenic plants will sole the storeroom problems, will ensure trouble-free liberation practice by feeding and will bear low cost as compared to the recombinant vaccines produced by bacterial fermentation. Vaccinating inhabit in contradiction of dreadful diseases like cholera and hepatitis B, by feeding them banana, tomato, and vaccinating animals in contradiction of focal diseases will be an out of the ordinary development.

Biodegradable plastics

Polythenes and plastics are individual of the major environmental hazards. Efforts are on to explore the opportunity of using transgenic plants in lieu of biodegradable plastics. Transgenic plants can be used as factories to deliver biodegradable plastics like polyhydroxy butyrate or PHB. Genetically engineered Arabidopisis plants can deliver PHB globules exclusively in their chloroplasts devoid of effecting conceal growth and development. The large-scale production of PHB can by far be achieved in plants like Populus, wherever PHB can be extracted from leaves.

Molecular Breeding
The tenure molecular breeding is regularly used to characterize the breeding methods to facilitate are coupled with genetic engineering techniques. Up turn over nowadays, usual breeding methods bear been used to experience the food load of the growing globe population and the challenges of poverty and improved crop production and yields. However in the years to be as long as, the development in the gardening yields and techniques is obtainable to be due to the habit of molecular breeding programme.
Linkage analysis which deals with the studies to correlate the link connecting the molecular marker and a desired mannerism is an focal aspect of molecular breeding programme. Hip the history, linkage analysis was accepted absent by habit of isoenzymes and the associated polymorphisms. Now a days, molecular markers are being used.

Molecular breeding involves breeding using molecular (nucleic acid) markers. A molecular marker is a RNA sequence in the genome which can be located and identified therefore molecular markers can be used to identify specific locations in the genome.

Due to mutations, insertions, deletions, and the like. The foundation constitution on a specific location might be atypical in atypical plants. These differences, termed polymorphisms, allow RNA markers to be mapped in a genetic linkage arrange.
Generally, at hand are three types of markers used in screening/selection:
A)         Morphological marker based on visible character (phenotypic expression) e.G. Flower color, seed color, height, leaf shapes, and the like. Morphological markers can be dominant or recessive. There are clear constraints in using these markers as the morphological markers are by far influenced by environmental factors and as a result might not characterize the desired genetic departure. Some of the visible markers bear not much role to take part in in the conceal breeding programme.
B)         Biochemical marker: The proteins produced by gene articulation are moreover used as markers in conceal breeding programmes. The largely commonly used are isozymes, the atypical molecular forms of the same enzyme. Each original variety has its own isozyme inconsistency (profiles) which can be detected by electrophoresis on starch gel.
C)         Molecular marker based on RNA polymorphism detected by RNA probes or augmented products of PCR, e.G.Restriction fragment span polymorphism (RFLP), Randomly Amplified polymorphic RNA (RAPD), adaptable Number Tandom Repeats (VNTR), Microsatellites, and the like. Plant breeders continually choose to detect the gene as molecular marker, although it is not continually probable. Molecular markers provide a exact representation of the genetic bake up on the RNA level. They are dependable and at no cost from environmental factors, and can be detected much sooner than the development of plants occur. The help with a molecular marker is to facilitate a conceal breeder can pick a right and proper marker in lieu of the desired mannerism which can be detected well in advance. A portly run to of markers can be generated as for every the needs. The molecular markers to be used in conceal breeding programme must bear the following characteristics: (a) the marker must be strictly linked with the desired mannerism, (b) the marker screening methods must be operative, efficient, reproducible and trouble-free to have available absent, (C) the intact analysis must be cost operative.

(a)   Molecular makers are of two types:  based on nucleic acid (DNA) hybridization- This involves the cloning of the RNA example followed by the hybridization with the genomic RNA, which is anon detected.
The Restriction fragment span polymorphism (RFLP) was the very principal tools employed in lieu of the detection of polymorphism, based on the RNA sequence differences. RFLP is for the most part based on the altered restriction enzyme sites, as a findings of mutations and recombinations of genomic RNA. The procedure involves the isolation of genomic RNA and it’s absorption by restriction enzymes. The fragments are separated by electrophoresis and in the end hybridized by incubating with cloned and labeled probes.

(b)  Molecular markers based on PCR amplification.
Polymerase shackle reply (PCR) is a novel procedure in lieu of the amplification of selected regions of RNA. The largely focal help is to facilitate even a infinitesimal quantity of RNA can be augmented and the PCR- based molecular markers require individual a small quantity of RNA to start with. Random augmented polymorphic RNA (RAPD) markers habit PCR amplification wherever the RNA is isolated from the genome and is denatured. The stencil molecules are annealed with primers and augmented by PCR. The augmented products are separated on electrophoresis and identified. Based on the nucleotide alterations in the genome, the polymorphisms of augmented RNA sequences fluctuate which can be identified as bends on gel electrophoresis.
Amplified fragment span polymorphism (AFLP) is a novel procedure linking a combination of RFLP and RAPD. AFLP is based on the assumption of generation of RNA fragments using restriction enzymes and oligonucleotide adaptors (or linkers), and their amplification by PCR.

Microsatellites
Microsatellites are the tandemly constant multiple copies of mono-, di-, tri-, and tetra nucleotide motifs. Hip about instances, at hand are unique flanking sequences contemporary in the replicate sequences. Primers are designed in lieu of such flanking sequences to detect the sequence tagged microsatellites (STMS) which is completed by PCR.

Commercial habit of transgenic plants
The central goal of producing transgenic plants is to multiplication the productivity. Hip 1995-96, transgenic potato and cotton plants were used commercially in lieu of the principal instance in USA. By the day 1998-99, five other major transgenic crops cotton, maize, canola, soybean, and potato were introduced to the farmers. These accounted in lieu of on the order of 75% of the come to area planted by crops in USA. There are still a allocation of concerns regarding the destructive environmental and dangerous vigor personal property of transgenic plants. The major areas of unrestricted disquiet are- the development of resistance genes in insects, generation of a super weeds by transmutation and the like. Certain other authorized and regulatory hurdles pertaining to mercantile habit of transgenic plants, needs to be addressed.

Bioethics in Plant genetic Engineering
There are issues and concerns regarding the habit of transgenic crops and their personal property on the vigor and the atmosphere in common. The major concerns on the order of GM crops and GM foods are:

A)         Effect of GM crops on biodiversity and environment- being the GM crops are twisted artificially, at hand is rejection natural process of evolution in their development. Hence, at hand is a question of this moving the biodiversity and overall effect on the atmosphere.

B)         The endanger of move of transgene from GM crops to pathogenic microbes- Antibiotic marker genes are used to identify and pick the modified cells. If GM food containing antibiotic resistance marker gene is consumed by animals and humans, at hand is a endanger to facilitate the transgene will move from GM food to microflora of person and animals. This might show the way to the gut microbes to befit impervious to to antibiotics.

C)         The move of genes from animals into Gm crops in lieu of molecular unindustrialized might replace the fundamental vegetable nature of plants.

D)         The GM crops might bring on the order of changes in evolutionary patterns. The plants adapt to the changing atmosphere in the natural way by changing their genes and emergent better races with superior traits which ultimately leads to the development of evolved races and varieties. What will be the evolutionary pattern of the GM crops? There are concerns on the order of the effect of transgene spring from GM crops to other non-GM plants and the alteration of these non-GM crops.

E)         There is a endanger of transferring allergens (usually glycoproteins) from GM food to person and animals.

F)         There is a endanger of “gene pollution” i.E. Move of transgene of GM crop through pollen grains to connected conceal species and development of super weeds.

G)         There are moreover about religious issues connected to the consumption of transgenic plants with subconscious genes introduced into them, especially, in lieu of about strict vegetarian inhabit and about ethnic groups with clear food preferences and restrictions.

H)         There is a need to study scrupulously as to how the genetically engineered plants will affect the ecological balance, in the past they are released in the atmosphere...

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