Transgenic crops: It is a modern technique in which organisms are genetically modified through transfer of desirable recombinant DNA. In this technique, artificially inserted one or more genes into recombinant DNA of unrelated plant or species.
Transgenic crops providing new ways to envision agriculture
Agriculture is a vast and gigantic field for food production in the Pakistan. Transgenic crops are important technique for providing and fulfillment of food for day by day increasing population in the globe. Even before the creation of transgenics, the alteration of crops to improve their production was performed through selection. In fact, this selection has been going on for thousands of years and only in the past few centuries has it become a dedicated science onto itself.
Simply put to manipulate plants through selection takes many generations and does not always work. Through the use of transgenics, one can produce plants with desired traits and even increase yields to allow for more crops that last longer and withstand pests and disease.
The idea being that we could produce the traits we want without throwing the dice as with selection techniques, allowing us to better feed a growing population and produce more desirable products. That’s the idea at least, but how exactly is it done? And should it be tried at all?
Molecular strategies for gene control in transgenic crops
For several years plant breeding demanded the selection of the finest plants to get the best crops. In those days, variation occurred through induced mutation or hybridization where two or more plants had crossed each other. Selection occurred through nature, using a selection of the fittest concept, where only the seeds best adapted to that environment succeeded.
For example, farmers selected only the biggest seeds with non-shattering seed heads, assuming these to be the best. Today, scientists can not only select, but also create crops by inserting genes to make a seeds bare any trait desired.
For transgenic crop five steps are involved, extracting DNA, cloning a gene of interest, designing the gene for plant infiltration, transformation, and finally plant breeding.
To understand this process, everyone should know about DNA (deoxyribonucleic acids). DNA is the universal programming language of all cells and stores their genetic information as well as genetic code. It contains thousands of genes, which are isolated segments of DNA that encode the information necessary to produce and assemble specific proteins. All genes require specific code in order to be utilized (or expressed) by a cell.
Gene Regions
- A promoter area, which signals where a gene begins and it used to express the gene;
- A termination sequence, which signals the end of a gene;
- And the coding region, which contains the actual gene to be expressed.
All these regions together permit a gene to produce a protein. Once a gene is transcribed into a protein, then it can be function as an enzyme to catalyze biochemical reactions or as a structural part of a cell, both of which will contribute to the appearance of a trait in an organism.
The process in which DNA is converted into Protein is called translation and all the organism have an ability to convert DNA into protein. This capability makes possible through artificially inserting of genes from one organism to another organism which is not applicable. For this we should know about specific segment of DNA to be inserted into another organism.
Unfortunately, with reference to producing new crops, we are unable to saying that which genes are responsible for increased crop yield, tolerance to different stresses and insects, color, or various other plant characteristics. Most of the research in transgenics is now focusing on how to identify and sequence genes contributing to these characteristics.
Genes that are determined to contribute to certain traits then need to be obtained in a significant amount before they can be inserted into another organism. To obtain the DNA comprising a gene, DNA is first extracted from cells and taken into a bacterial plasmid. A plasmid is a molecular biological part that allows any segment of DNA put into a carrier cell usually a bacterial cell and replicated to produce new cell.
A bacterial cell i.e. E. coli that contains a plasmid can put aside and used repeatedly to produce copies of the gene the researcher is interested in, a process that is generally referred to as cloning the gene. The word cloning referring to producing new identical copies of the cell. Plasmids containing this gene can be used to modify the gene in any way the researcher sees fit, allowing novel effects on the gene trait to be produced.
Once interested gene has been enlarged, it is time to introduce it into the plant species where we are interested in. The nucleus of the plant cell is the target for the new transgenic DNA. There are many methods of doing this but the two most common methods include the Gene Gun and Agrobacterium method.
Here is another new technique Gene Gun, also known as the micro-projectile bombardment method, it is very commonly used in crops such as corn and rice. As its name indicates, this procedure contains high velocity micro-projectiles to carry DNA into living cells using a gun. It involves stabbing DNA to small micro-projectiles and then firing into target cell. This technique is clean and safe.
It enables scientists to transform organized tissue of plant species and has a universal delivery system common to many tissue types from many different species1. It can give rise to un-wanted side effects, such as the gene of interest being rearranged upon entry or the target cell sustaining damage upon bombardment. Nevertheless, it has been quite useful for getting transgenic into organisms when no other options are available.
The Agrobacterium method involves the use of a soil-dwelling bacterium known as Agrobacterium tumefaciens, which has the ability to infect plant cells with a piece of its DNA. The piece of DNA that infects a plant is integrated into a plants chromosome through a tumor-inducing plasmid Ti plasmid, which can take control of the plant’s cellular machinery and use it to make many copies of its own bacterial DNA. The Ti plasmid is a large circular DNA particle that replicates independently of the bacterial chromosome (see Figure 1.3).
The importance of this plasmid is that it contains regions of transfer DNA (tDNA), where a researcher can insert a gene, which can be transferred to a plant cell through a process known as a floral dip. A floral dip involves dipping flowering plants into a solution of Agrobacterium carrying the gene of interest, followed by the transgenic seeds being collected directly from the plant.
This process is useful and it is a natural method of transfer and therefore thought of as a more acceptable technique. In addition, Agrobacterium can transfer large fragments of DNA very efficiently without substantial rearrangements, followed by maintaining high stability of the gene that was transferred. One of the biggest limitations of Agrobacterium is that not all-important food crops can be infected by this bacterium.
Constraint of transgenic crops
Plants have been improved for many reasons over the years but the most common purpose is to produce the best production. Before the use of recombinant DNA technology, it was possible to produce some improved products, although it was very difficult to do and many things could not be improved or changed. An improved product may involve changing the color or the size of a plant, making it more attractive to the buyer’s sense.
Or it may be more practical, allowing increased tolerance to cold, frost, or drought; all making a crop easier to grow in a constantly changing environment. Goals like these are unattainable with traditional selection programs and thus transgenes is now preferred when trying to come up with new products to improve sales. One of the hottest areas right now is the modification of crops to increase the resistance of plants to insects and diseases they may carry.
Now the use of transgenic crop reduces the use of pesticides and herbicides against disease and weeds. Insects also reduce the need for herbicides. Through It now the cost of production has been reducing and increases the benefit of farmer and as well as consumer. In short, transgenic crops are an economically sand useful method for producing crop products, which makes them appealing and potentially profitable.
Merits and demerits of transgenic crops
The use of transgenic crops has been an issue for many years. Many concerns have been raised and these generally fall into two categories:
Merit
A concern about what affect genetically modified material could have on human health. Transgenic crop causing allergies in some people, moreover it is inexact whether transgenic crops are the source of this reaction. Furthermore the antibiotic resistance genes placed in these crops has been suggested to cause resistance to antibiotics leading to super bugs that cannot be killed with antibiotic treatments.
The idea of a population being uncomfortable with ingesting DNA that originated from another source, such as a virus or bacteria, must also be considered when thinking about producing transgenic crops. However, to date, there is no evidence of the DNA from transgenic crops being any different from the DNA ingested from conventional crops.
Demerit
Transgenic crop destroying the natural environment with respect to weather. Pollen from which is transfer from transgenic corn, they killed the Monarch butterfly larvae. It has been shown that hybrid corn expresses a bacterial toxin in its pollen, which is then dispersed over sixty meters by wind. In this range, the corn pollen is deposited on other plants near cornfields where it can be ingested by non-target organisms including the monarch butterfly. These butterflies have been found to eat less, have a slower growth rate and higher death rate.
A second example is the hybridization of crops with nearby weeds. This could cause these weeds to attain resistance to herbicides or other things that we have been trying to avoid for many years. Genes that provide resistance to viral disease or other traits allowing them to survive in their environment could end up benefiting weed populations around a crop field. This trait could make that population more difficult to control. To date, there has been little evidence to support this theory.
On other side of the coin are the notions that support the use of transgenic crops. The potential benefits of which are obvious, including such things as increased yields to feed a growing population, decreasing the use of pesticides to save the environment and the cost of pesticides, and the production of novel crops such as providing crops with increased nutritional value Being able to retrofit any crop to our desires is a powerful concept, especially with the changing climates of today.
Sadaf Khan1* and Arshad Ali2.
1Taxonomy lab, Department of Botany, University of Agriculture, Faisalabad
2Postgraduate Lab, Department of Agronomy, University of Agriculture, Faisalabad