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The New Green Revolution
The green revolution which gave us plenty of grains to feed millions of people and the revolution in medicine which increased the life span of man are common knowledge even to lay people. All this was possible due to major discoveries and technological innovations in agriculture and medicine. Today, we are witnessing another revolution in biosciences because of some major advances in cell biology and genetics.
Many people are inclined to believe that while the battle for green revolution of the type we saw three decades ago was fought in the field, the battle for the new revolution in biosciences known as "Biotechnology" is being fought in modem laboratories.
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Some argue that the new biotechnology in agriculture is the second green revolution (part II) which will speed up crop improvement by gene manipulation in a Petri dish rather than in an open field.
The meaning or the definition of the word biotechnology has been the subject of hot debate by scientists and technocrats. The definition depends on the extent of expertise a group or an individual has with regard to cell biology. It also depends on the needs of a society or a country one lives in. The use of microorganisms or their products for food, feed, biofertilizers, biopesticides and medicine was known during the last 60 years.
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The major developments in medicine and industry during those years came with the use of microorganisms for the benefit of mankind through new inventions in microbial technology and fermentation processes but the biotechnology of which we are currently talking about is envisaged by splicing genes and altering genomes by insertion of foreign DNA by genetic recombinant DNA techniques (the so-called genetic engineering).
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The cell which is being manipulated by genetic recombination may be a microbial cell or a cell from a tissue of a plant, animal or man with the ultimate objective of inserting or cloning useful genes to obviate the use of long and tedious process of conventional breeding often replacing it by tissue culture techniques.
David Baltimore, Nobel Laureate, formerly Director, Whitehead Institute and Professor, Department of Biology, Massachusetts Institute of Technology defined Biotechnology as the application of scientific and engineering principles to the processing of materials by biological agents to provide goods and services. The author defines biotechnology as the application of science and technology to accelerate or improve nature's processes in producing man's ever increasing needs for a good living.
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The path from green revolution to gene revolution or from conventional plant breeding to genetic engineering has been filled with many significant findings. For almost a century plant breeders identified and selected desirable characters and combined them into one individual plant.
Since all characters are controlled by genes in chromosomes, plant breeding may be regarded as manipulation of chromosomes.
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This was done by the sorting and retention of similar chromosomes in the same plant to reach a homozygous state, a method termed pure line selection. Alternatively, different chromosomes can be combined to form a heterozygous state, a method known as hybridization conferring hybrid vigour or heterosis.
The next step was the development of genetic variability through spontaneous or artificially induced mutations. Normal plants are diploids but when plants are developed with three or more sets of chromosomes, they become polyploids that' tend to be bigger than diploids. Autopolyploid plants have genes similar to their diploid ancestors whereas allopolyploids are combinations of genomes of two different species that differ in characteristics.
The first achievement of hybridization techniques was the develop¬ment of hybrid maize in 1919 which revolutionizep American agriculture. The development of hybrid wheat and rice plants in 1960s filled the bread basket of developing countries, generally known as green revolution, for which Dr. Norman Borlaug was awarded the Noble Peace Prize in 1970.
The discovery that plant cells can develop into entire plants was another land mark in the development of new varieties of crop plants. The term tissue culture was coined to denote the in vitro development of plants in test tubes from calluses generated from plant parts. This led to mass production of uniform plants and revolutionized floriculture in the globe. Tissue culturing often leads to progenies which are variable. These progenies are known as somoclonal variations and have been exploited to generate mutations and it has been estimated that in vitro tissue cultures can produce ten times more somoclonal variations than that can be induced by chemical mutagens.
Fusion of naked genetically compatible protoplasts (inter specific) resulted in successful regeneration of new varieties. Fusions between incompatible protoplasts (inter generic) resulted in abortive cell division and successes in regeneration was never achieved, excepting the instance of crossing between tomato and potatoes forming 'pomatoes' which can only be regarded as a laboratory success not amenable to commercial exploitation.
With the advent of biotechnology, agriculture has reached a science based industrial state. By using recombinant DNA technology, many transgenic life forms have been engineered since 1985. Transgenic plants belonging to both monocotyledonous plants such as maize, millet, wheat, rice and ragi and dicotyledonous plants such as alfalfa, clover, peas, soybean, mothbean, potato, tobacco, cotton, flax, sugarbeet and sunflower have been constructed. New varieties of vegetables and fruits such as cabbage, carrot, cauliflower, celery, cucumber, horseradish, lettuce, rape, grape, muskmelon and strawberry have been developed. The new varieties have incorporated genes capable of resisting one or more of the following: herbicides, insects, stress, frost or virus infections.
Plant biotechnology has opened up the possibility of producing artificial seeds, artificial sweetners (sugar substitutes) and bioplastics. Normal seeds have an embryo surrounded by cotyledons for initial sustenance during germination. By somatic hybridization, plant embryos can be mass multiplied in fermentation tanks and each embryo is then encapsulated in a jelly-like coat that can be called an artificial seed. Some estimates have revealed the possibility of production of 80,000 embryos per day but the cost could well be prohibitive for commercial exploitation. Presently, several companies are engaged in reducing the cost for atleast some crops such as carrots and celery.
The most important sugar substitute is the maize based high fructose com syrup (HFCS) known as isoglucose in Europe. Some estimates put HFCS production worldwide to 6 million tonnes available in liquid as well as crystal form.
Aspartame is a synthetic chemical thousand times sweeter than sugar. With the advent of this product nearly 38 research institutes and companies around the world are engaged in producing novel chemical sweetners.
Thaumatococcus danielli or commonly known as Katemfe is a plant that grows in humid forests in Western and Central Africa. The berries of this plant contain the protein thaumatin that is 2500 times sweeter than sugar. Tate and lyle, a UK based sugar company had set up plantations of Katemfe in Ghana, Liberia and Malaysia. The frozen berries were processed to obtain purified thaumatin that was sold under the brand name 'Talin'. One drawback of thaumatin is its lingering taste limiting its use in food products. In spite of this, research is underway to understand the gene coding for thaumatin and its transfer to E. coli and other plants.
Stevia rebaudiana grows in Paraguay and several countries in South East Asia. The plant is capable of producing proteins several hundred times sweeter than sugar. The product is being marketed in Japan which has also bitter taste. African forests abound in sweet berries such as 'Miraculous berry' (3000 times sweeter than sugar) and Mexico has Lippia dulcis, thousand times sweeter than sugar. The search for cheaper substitute to cane sugar is being pursued vigorously and in future years we may have alternate sugar sources.
An interesting example of how a plant can be made to produce novel chemicals such as bioplastics is the transgenic Arabidopsis capable of producing granules of polyhydroxybutyrate (PHB), a polyester which is normally obtained from the bacterium Acaligenes eutrophus. In fact, PHB is a storage product in many bacteria intended to be used as a source of energy by bacterial cells in times of nutritional stress. This bioplastic material is a delicate product destroyed by pH above 8 and temperatures above 70°C. The product is mixed with polyhydroxyvalerate (PHV) to make it flexible and moulded into any shape, spun as fibre or rendered into a film. It is biodegradable to CO2 and H2O with no environmental hazard. The bioplastic is compatible with living tissue and hence can be adapted for medical purposes. It can also be used as a much in agriculture.
Transgenic animals and microorganisms are being used for fundamental research, for production of pharmaceuticals such as goats-Iactoferrin and for production of biological control agents. Pigs and rabbits are genetically engineered to function as organ donors for human beings and chickens have been exploited for producing foreign proteins in eggs. Pharm biotechnology (agricultural production of pharmaceutical products) has to be distinguished from Farm biotechnology (productivity related agricultural applications) and very likely agriculturally produced pharmaceuticals will be marketed sooner than agricultural products, despite the fact that the latter could undoubtedly increase global food supply.
This has been due to success in pharmaceutically oriented animal experiments as exemplified by the transgenic modification of pigs and sheep for expressing valuable pharmaceutical products in milk where all animals in the offspring appeared healthy contrasting with the transgenic pigs generated to produce leaner meat or more rapid growth whose offspring had adverse effects.
There are about 20 different man made pharmaceuticals involving crops that have been genetically changed to produce a range of prophylactics from cholera vaccines, herpes vaccine and cancer treatments. Potatoes seem to be ideal vehicles for the new generation of vaccines such as vaccine against E. coli disorders of the intestine. These are friendly and easier to tolerate than injections.
Phosphorus in seeds is a poor nutrient for monogastric animals such as chickens unless phytase is present to release phosphorus. Feeding chickens with seeds containing the phytase gene from Asperigillus niger brought about growth increases in chicken. This biotechnological innovation known as "gene farming" not only improved the quality of chicken feed but also minimised the excretion of phosphate in the environment. Another example is the case of sweet potato which is a staple food in China. The strategy here was to implant twin genes such as viral coat protein gene and Bacillus thuringiensis genes into sweet potato to ward off diseases caused by viruses as well as insect pathogens.
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