by Asis Datta,
Vice Chancellor, Jawaharlal Nehru University
Since the complete sequence of genome was first reported, there has been a dramatic increase in DNA sequence information for plants. Notably, the Synechocystis PCC 6803genome has been sequenced, a second photosynthetic prokaryote genome is >40% complete; Arabidopsis genome is nearly sequenced and will be complete well ahead than the target time 2005. A comprehensive list of more than 39,000 polymorphism has been released. Rice genome should be completed in next three years. We are just entering into post genomics era and now the question is : how will we make use of this wealth of sequence information? The information has to be translated into application genomics into nutritional genomics, in particular. The term nutritional genomics is used to describe work at the interface of plant biochemistry, genomics and human nutrition. Modifying the nutritional composition of plant foods is an urgent worldwide health issue, as basic nutritional needs for much of the world's population are still not met. Nutritional genomics is more than biology; it is also about producing better food and feed for our planet. The goals: science is to increase crop productivity, improve crop quality, and maintain the environment. Genetic improvements in crop plants beyond current capabilities are needed to meet the growing world demand not only for more food, but also for a greater diversity of food, higher quality food, and safer food, produced on less land, while at the same time, conserving soil, water, and genetic resources.
The potential applications of plant biotechnology can play a critical role in the betterment of farming systems in the next millennium. Plant biotechnology will facilitate the farming of crops with multiple durable resistance to pests and diseases, particularly in the absence of pesticides. Likewise, transgenics and marker assisted selection may assist in the development of high yielding crops, which will be needed to feed the world and save land for the conservation of plant biodiversity in natural habitats. Hence, crops should be engineered to meet the demands and needs of consumers. The genetic base of crop production can be preserved and widened by an integration of biotechnology tools in conventional breeding. Similarly targeting specific genotypes to particular cropping systems may be facilitated by understanding specific gene by environment interaction(s) with the aid of molecular research. High quality crops with improved nutritional and health characteristics as well as other aspects of added value may be obtained through multidisciplinary cooperation among plant breeders, biotechnologists and other plant scientists. Coordinated efforts between consumers, policy makers, farmers and researchers will be required to convert the various aspects of a crop ideotype into components of new and improved farming systems.
The use of transgenic crops may indeed have a beneficial effect on the environment by significantly reducing the use of agro chemicals. Other genes for improving crop productivity and manipulating starch/protein/oil quality and quantity, as well as resistance to stresses such as temperature, drought, and salinity/metal toxicity, are also being isolated and studied. Progress is being made in the use of transgenic plants to produce therapeutic proteins and pharmaceuticals, and even edible vaccines. Manipulation of photosynthetic efficiency and flowering time, and source/sink relationships, could be used in the future to increase crop yields.
The plant genomics has revolutionized agricultural research; a series of important traits in crops of economic importance, woody trees, horticultural, and ornamental crops can be addressed from a general perspective using gene function analysis from model plants. The initial phase of this revolution in agriculture has already occurred. Large areas of genetically modified (GM) crops of soybeans, corn, cotton, and canola have been successfully grown in the Western Hemisphere. In the United States in 199.9, of the total of 29 million hectares planted with soybeans, half were planted with GM herbicide resistant seeds. When heibicide resistant seeds were used, weeds were easily controlled, less tillage was needed, and soil erosion was minimized. At present transgenic cotton, soybean and corn account for 18%, 13%, and 9%, respectively, of the national acreage in the United States, while 25% of the canola grown in Canada is transgenic.
For more than a decade, we have been involved in nutritional genomics. One of our goals of nutritional genomics has been to create crops that are tailored to provide better nutrition for humans and their domestic animals. A major target has been the improvement of nutritive value of crop plants, in particular the amino acid composition. Towards this end, we used an amaranth seed albumin gene (AmAl) to develop GM crops. The AmAl protein is non allergenic in nature, rich in all essential amino acids and its composition correspond well with the World Health Organization standards for optimum human nutrition. Potato is the m6st important non cereal food crop and ranks fourth in terms of total global food production. The essential amino acids that limit the nutritive value of potato protein are lysine, tyrosine and the sulphur amino acids methionine and cysteine. In an attempt to improve the nutritional value of potato, the AmAl cDNA was successfully introduced and expressed in tuber specific and constitutive manner. There was 3.0 to 3.5-fold increase in tuber yield in terms of fresh weight and at least 2 fold increase in tuber number in transgenic populations. A 35 45% increase was also observed in total protein content with broad correlation in increase in most essential amino acids. In addition, to remove the nutritional stress factor namely oxalic acid from some commonly used vegetables, the coding region of OXW gene isolated from a wood rotting fungus was cloned and over expressed in tomato plant as it has high content of oxalic acid. Transgenic tomatoes showed stable expression of the foreign protein and also accumulated very little oxalic acid in comparison to wild type plants. Apart from this, the transgenic plants were found to be resistant to infestation by Sclerotinia sclerotiorum.(Summary by Professor Datta)