From the earlier articles you would have understood the imperative need of biotechnological approaches in crop improvement for ensuring food and nutritional security. In this issue let us make you clear about the origin of the idea of genetic modification and how actually the GMO’s are produced.
For millions of years, the earth has witnessed tremendous changes in its physical structure and life forms. But with the evolution of six sensed human beings, the changes are extremely fastened in the past few thousand years and he has become the superior being on earth only because of his thinking ability. He has born; he observed nature; he learned; gained knowledge from fire to flights; nature taught him all and made him superior over other life forms on earth. The same nature has sparked a modern day scientist to develop genetically modified organisms which are actually not against nature but from nature.
Microbes are the most diverse life form on our planet and several breakthroughs in biology have come through microbes. Scientists started looking microbes more closely with advanced technologies and tried to understand the mechanism by which one living organism (microbes/plants/viruses) manipulates the genetic makeup of other living organism for its survival. The real light on GMO development was made due to the discovery of restriction enzymes (which cuts DNA molecules) and ligase enzymes (which joins DNA molecules) from bacteria. Bacterium acts as a major source of restriction enzymes which it employs to protect itself from the attack of viruses (bacteriophages). These biological molecules are popularly called as molecular scissors as it involves cutting and pasting. This biological mimic has led to an era of ‘‘recombinant DNA technology’’. This natural phenomenon made a major breakthrough in the field of biological sciences with the development of genetically modified microorganisms, plants and animals, recombinant insulin, recombinant vaccines, transgenic plants etc,.
You all think that plant scientists are the first to produce transgenic crop plants. Is that true? You will be surprised to know that a tiny soil bacterium can do this naturally. Plant genetic transformation technique was actually adopted from the natural soil dwelling bacteria Agrobacterium tumefaciens which is popularly called as “natural plant genetic engineer’’ or ‘‘Wonder bacterium’’. It has a unique ability to transfer a part of its genetic material (DNA) into the plant nucleus which gets integrated into the plant genome. This plant pathogenic bacteria causes crown gall disease in plants particularly among the members of dicots, in order to make the plants (acts as a host for the bacteria) to produce nutrients (carbon and energy) solely utilized by A. tumefaciens for its survival. This plant–microbe evolution was happening for several thousand years. Scientists have discovered this unique phenomenon and replaced the disease forming DNA fragment with the DNA fragment or a gene(s) of interest (Insect resistant, herbicide resistant, stress tolerant genes, etc.,) and delivered genetically engineered material using this bacterium to produce GMO’s. Now the transgenic plants will produce desired traits instead of galls. This method has been standardized in several cultivated crop species and utilized for crop improvement. Even though direct DNA delivery methods (like Gene gun) are available, most of the laboratories across the globe are utilizing A. tumefaciens-mediated method of transformation to produce transgenic plants because of its advantageous features. Few other microbes with the same ability to transfer genes have been discovered in recent times. This inter-kingdom (from microbe to plants) gene transfer is one of the best example to prove against those who claim this science as unethical and unnatural.
In 1901, a soil bacterium was identified to have an effective insecticidal activity against major crop pests. Farmers used the liquid formulation of this bacterium for several years to protect their crops from herbivorous insects. The name of this revolutionary bacterium is Bacillus thuringiensis. But the major disadvantages of topical Bt pesticides are their shorter time of effectiveness and failure to persist in the target plants in changing environmental conditions (inactivation by UV light, heat, extreme pH). To overcome these problems, during 1980s, the advancement in molecular techniques enabled scientists to isolate the gene (popularly called Bt gene or cry gene) responsible for such insecticidal activity and transferred to several important crop plants to achieve built-in protection against insect pests. This natural gift is playing a phenomenal role in improving the livelihood of farmers cultivating Bt transgenic crops all over the world. Furthermore, in environmental perspective, it majorly reduced the use of chemical insecticidal sprays. Hence, it can be strongly claimed that this is an effective organic way of cultivation as it involves the use of a gene from a free-living soil microorganism without the need for any artificial chemicals!!! We will discuss about Bt crops in detail in our upcoming articles.
Genetic modification is involved not only in introducing new genes from various sources but also in editing the genome of an organism. It plays major role in altering the target genes to produce specific characteristics of our interest by switching the gene on or off (fruit ripening, flower color modifications, virus resistance). Mutation (slight alteration in DNA sequences) occurs in all organisms including humans. Based on this natural phenomenon scientists have used several methods to alter the traits of their interest by editing the DNA sequences. In crop like tomato, the ripening process was slowed down by altering the gene involved, to reduce the damage or loss caused during transportation. Recently scientists have developed a non-browning apple and mushroom using CRISPR/Cas9 genome editing tool to disrupt the genes involved in browning process in order to increase the shelf life of these commodities. It will be exciting for you to know that these genome editing techniques also got adopted from mechanisms carried out by certain microorganisms naturally. Similarly, several other life forms on earth are serving as powerful genetic resource for traits like salinity tolerance, drought tolerance, high temperature tolerance, frost tolerance, etc,. There are transgenic crop plants being developed and commercialized successfully with such traits.
Discoveries and inventions keep on changing overtime and occur in need basis. Methods which we claim now as traditional would have been a modern technology once upon a time. Similarly, the present day modern techniques may become a traditional technology by the year 2500. Ayurvedic medicinal practice (use of herbs, metals, exercise, and diet) which we consider now as a traditional method might have got some opposition when it was first introduced 3000 years ago. But both Ayurveda and modern day biotechnological tools use naturally available resources to solve particular problems. So in the present scenario, public acceptance of biotechnological interventions are really essential to use or modify these natural genetic resources (genes) in producing crop plants with traits that are necessary for sustainable agriculture and to ensure food and nutritional security under ever-threatening biotic (pests & pathogens) and abiotic (climate change) stress conditions.
(Note: Genetic modification is a naturally occurring process in all organisms. Even a conventional plant breeder modifies the genetic component of a plant to bring about his desired trait. Owing to the popularity and better understanding, it has been mentioned in this article as genetically modified organisms (GMO’s). But the exact scientific term to describe these genetically transformed crops is genetically engineered organisms (GEO’s) or GE crops.)
-By Godwin James, Ram Sankar. C, Nandha Kumar. S and Ragavendran Abbai. Biotechnology graduates currently pursuing post graduate in their field.