What is Agricultural Biotechnology? Biotechnology is not a new era of scientific endeavour: microorganisms have been used to produce food such as beer, vinegar, yoghurt and cheese for over 8 millennia.
Simply put, Biotechnology is the use of living cells or microorganisms (e.g. bacteria) in the industry and technology to manufacture drugs and chemicals, break down waste, etc.
More technically put, Biotechnology is an area of multidisciplinary science, involving a variety of distinct subjects, where living organisms or their useful parts are put into effective use to cater for the welfare of humanity. It may be grouped into:
- Conventional Biotechnology
- Modern Biotechnology
Biotechnology is considered a powerful tool that can, in a quick and through manner, bring what is most lacking in agriculture.
Question of safety of biotechnology products to man and the environment has been considered alongside Biotechnology programmes.
In most developing countries of West and Central Africa where food is produced for instance, famine, poverty, and malnutrition remain huge constraints in rural as well as urban areas.
Interestingly, though, agriculture, which makes up forty percent of export revenue and thirty-five percent of the gross domestic products of West and Central African revenue, employs seventy percent of the labour force and covers endless agro ecological lands.
Significantly, in many industrialized countries, biotechnology has contributed to progress in agriculture, while, in developing countries, it comes to add itself to the many technological tools to achieve crucial productivity and sustainability targets, to increase food production on the same land surface areas or less, with added nutritional value and projected lesser negative impact on environment.
However, large-scale use of biotechnology has its own constraint: skilled human resources are limited; material and financial resources are lacking; the controversies about some agricultural biotechnologies, such as the genetic engineering and products from this new technology, remain widespread and time consuming.
In any case, given to the skyrocketing rural population growth, its dependency on agricultural production systems highly vulnerable to climatic changes, the scarcity of fertile lands per head, need to increase and improve agricultural production has become definitely very important.
The emergence of biotechnology over the last few decades has opened new doors for increased productivity not only for agriculture but also in medicine and industry.
It is of particular relevance to developing countries that are confronted with an ever increasing population, food shortage, and scarcity of economic resources.
Harnessing of solar energy to improve photosynthetic bacteria as well as utilization of agriculture and organic wastes to produce methane using biogas plants are also aspects of biotechnology in vogue.
The same is true of biological nitrogen fixation, a prerogative of certain free living or symbiotic anaerobic and photosynthetic bacteria and algae. Biotechnology has been employed in biofuel production and in biological cleanup of contaminated soil.
Applied to the economies of countries in the sub-region, biotechnology offers additional technological opportunities capable to responding to the constant demand for food and to reducing vulnerability in the agricultural sector.
As a result, it contributes to income generation, improving of nutrition and preservation of natural resources and ecosystem services. It is necessary to ascertain whether biotechnologies can supply rapid, safe, cost effective solutions to the intractable biotic and abiotic constraints.
The institutional and infrastructure constraints to agriculture are amenable to positive human intervention, and could facilitate rapid adoption of the yield and quality enhancing biotechnologies.
Whether biotechnological solutions are employed is a matter of consumer demand and need, and the resolve of politicians and regulators to deal with these issues in a science and fact based manner with due resolve.
Conventional Biotechnology
In the early days, biotechnologists used living organisms for the manufacture of a variety of useful materials. Whatever by-products were obtained during normal cell growth, were used by people.
For example, during the normal growth of yeast cells in grape juice, sucrose is converted to ethanol and this fermented juice, containing alcohol, is used as wine.
Similarly, Penicillium notatum and P. chrysogenum produce the antibiotic penicillin as a by-product of their secondary metabolism and this compound is used to fight microbial diseases.
Microbial production of glycerol by yeast, acetone and butanol fermentation using Clostridium acetobutylicum, citric acid production by Aspergillusniger and Streptomycin production using Streptomycesgriseus are some of the fields developed under conventional biotechnology.
Modern Biotechnology
More recently, plant tissue culture or micro propagation has become a useful technology, involving the principle of TOTIPOTENCY, enabling a cell to segment into a whole plant in the proper medium.
The production of biotechnology based plants, such as orchids, bamboos and a host of others has lead to export oriented industries in some developing countries like India.
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Rapid production of disease free clones of crops like yam, cassava, banana and plantain has been possible through tissue culture technique.
Modern biotechnology enables an organism to produce a totally new product, which the organism does not or cannot produce in its normal course of life. Since this means we are able to engineer a new genetic potential in an organism, this technology is also called GENETIC ENGINEERING.
Technically put, Genetic Engineering is a technology in which a gene or genes are taken from one organism (the donor) or are synthesized de novo (afresh), possibly modified and are then inserted into another organism (the recipient) in an attempt to transfer a desired trait or character.
The technique is also called Genetic Modification (GM), gene manipulation, recombinant DNA technology, gene splicing, bioengineering … and many other things!
Similar cell-fusion between plants and microorganisms through protoplast fusion and transfer of nitrogen fixing nodules, specific genes from legumes to non-legumes, had led to interspecific hybridization, and the impact of these methodologies in various facets of agriculture cannot be over-emphasized. Basic techniques, which stimulate the progress of modern biotechnology include:
- Recombinant DNA manipulation (genetic engineering)
- Plant and animal tissue culture
- Protoplast fusion
- Monoclonal antibodies
- Protein engineering
- Immobilized enzymes and cell catalysis
- Biosensors
- Computer-aided bioprocess
- New reactor design
- DNA transfer into living cells
- Polymerase chain reaction
- Chromosome engineering
Tools of Agricultural Biotechnology and Terms Defined
There are four main steps in making a transgenic organism, the process being termed
Transformation: There are several sources (donors) of this basic unit for genetic manipulation. One can take a gene from another variety of the recipient, from another species, genus or family or even from another kingdom (animal, plant, fungi or bacteria).
As the nucleic acid of the gene is likely to be known, one can even synthesize a gene denovo(afresh) in the laboratory.
An important tool in the molecular biology “tool kit” for isolating genes and for assembling the elements that are introduced into recipient organisms are RESTRICTION ENDONUCLEASES also known as restriction enzymes.
These are enzymes that cleave the double-strand of DNA at specific sites thus enabling the discrete isolation of a specific DNA sequence.
These specific pieces of DNA can be joined to other pieces in a directed manner using the enzyme DNA LIGASE.
The DNA that is introduced into plant cells during the process of transformation is termed a CONSTRUCT.
A construct contains the DNA sequence conferring the trait, the DNA elements involved in expressing the gene (the promoter, terminator and any control sequences), and one or more SELECTION MARKER genes.
The DNA sequence conferring the trait can be either the gene of interest or DNA that transcribes to give RNA that is complementary to a sequence in the target organism; the latter is termed antisense RNA or RNAi and can induce a process called RNA silencing.
The selection markers are used to select the transformed cells from those that are not transformed as the process of transformation can be inefficient (see below for more on selection markers).
These DNA elements are assembled into one or more DNA molecules. In some transformation strategies, the introduced construct comprises both the gene and the marker(s) on the same DNA molecule; in other transformation strategies (co-transformation), the gene and markers are on separate molecules.
Having assembled the construct, one has to amplify it to provide enough material to introduce into the plant cells. This is usually performed in bacteria by introducing the construct into a bacterial PLASMID; this is termed CLONING.
Various selection markers are used to select the transformed bacteria from the non-transformed bacteria. These include antibiotic resistance genes, which are of special significance in risk assessment.
There are approaches that do not involve antibiotic resistance markers, such as the blue-white colour selection method and herbicide-tolerant markers. Having isolated the gene, and having made and amplified the construct, it can be introduced into recipient’s cells.
The basic strategy for transforming a plant involves delivery of the construct(s) containing the gene(s) to the target material, selection of the transformed cells, and then regeneration of the transformed plant lines.
As noted above, the construct comprises an expression unit containing a selectable marker (which may be different from that used in the bacterium during the amplification stage) and an expression unit containing the gene of interest.
There are three basic gene delivery systems but only two are in general use for plant transformation.
The most frequently used direct transfer method is BIOLISTICS, also known as the gene gun, where the construct DNA is coated onto small gold or tungsten particles which are then “shot” into the target cell material.
The most commonly used indirect transfer method involves AGROBACTERIUM (Agrobacterium-mediated transformation).
Agrobacterium is a plant-pathogenic bacterium that contains a plasmid that has the ability to insert part of its DNA into the chromosome of plants.
For transformation of animals such as fish the construct is usually microinjected into fertilized eggs.
The constructs are then delivered into the target materials. Details of target materials differ between plant species and even between varieties of a species. One of the most important constraints is the ability to regenerate new plants from the target material, i.e. that the transformed cells have totipotency.
Thus there is a wide variety of target materials, the most common being immature embryos and embryonic cell suspension (note that GUS = B-glucuronidase and GFP = green fluorescent protein, both being colour marker genes).
Other targets include meristems, protoplasts and even flowers. As noted above eggs are frequently used recipient targets for animal systems.
Totipotent: blastomeres that can develop into complete individuals when separated, or, cells capable of forming any cell type.
Blastomere is any one of the cells formed by the first divisions of a fertilized egg.
Clone: a group of genetically identical individuals or cells derived from a single cell by repeated asexual divisions. Or, to produce a set of identical individual cells or DNA molecules from a single starting cell or molecule.
In most of the targets the construct is inserted into nuclear DNA and hence is passed between plants during fertilization. This causes the potential risk of transgenes spreading from transformed to non-transformed plants or animals.
The chloroplasts of plants are usually inherited maternally and hence a transgene would not spread in pollen.
Methods of chloroplast transformation are being developed which should mitigate some of the potential problems of gene flow.
This approach cannot be used with animals which do not have chloroplasts. The development of mitochondrial transformation is in the very early stages both for plants and animals.
When the gene construct(s) have been delivered to the target, those cells into which there is actual integration of the input DNA have to be selected away from those that have not been transformed.
There is a range of selectable markers, which, as with the selection markers for the bacteria in which the constructs are amplified, are an important aspect of biosafety risk analysis.
The final stages in the production of transgenic organisms are the regeneration of the transformed material.
For plants this can take a long time and requires much effort for animals, the transformed eggs are replaced into a suitable female or are cultivated in the laboratory.
Then the transformed organisms have to be analysed; this will be discussed extensively during this course.
Each independently transformed individual is termed a TRANSGENIC EVENT and the individuals derived from a transgenic event are termed a TRANSGENICLINE.
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