Genetic Engineering For Nitrogen Fixation

There is a time in scientific research when a number of developments coincide making it possible to progress with a tough and complicated problem. It is believed that such a time has come in the area of biological nitrogen fixation. A better understanding of photosynthesis, cell hybridization, plasmid, and gene transfer between cells not necessarily genetically related, have opened new avenues of research. New developments in traditional genetics, cell biology, biochemistry, including enzyme chemistry, and plant physi ology have brought about the feeling this is a most appro priate time to pull together the different approaches in a conference where the lines of research could be discussed and thus help to speed up developments in this area. What makes biological nitrogen fixation especially im portant is the promise that a good understanding of the basic problem would help us to make organisms more amenable to fix nitrogen, not only in symbiosis with legumes, but also with other plant species and develop a wider variety of organisms with the ability to fix N • It will also 2 encourage a search for naturally occurring N2 fixing organ isms other than the traditional N2 fixers. Some success has already been encountered in this area. Success in broadening the field of nitrogen fixing would help to increase food supply, especially in de veloping countries which cannot afford to purchase synthetic nitrogen sources.

The present volume developed from a symposium entitled "Enhancing Biological Production of Ammonia From Atmospheric Nitrogen and Soil Nitrate" that was held at Lake Tahoe, California in June, 1980. The meeting was supported by the National Science Foundation, Division of Engineering and Applied Sciences and by the College of Agricultural and Environmental Sciences, University of California, Davis. A total of 99 scientists from 41 insti tutions participated. Plants capture solar energy in photosynthesis and use mineral nutrients to produce human food and fiber products. The extent to which such materials are removed from agricultural production sites represents a permanent drain of mineral nutrients. Some plants of agronomic importance such as alfalfa, soybean, and clover associate with soil bacteria and use photosynthetic energy to reduce N2 to NH3. Many other free-living bacteria and some symbioses involving procaryotes and eucaryotes also reduce N2. Such processes repre sent one natural mechanism by which Man can augment soil N for agronomic purposes without using fossil fuel to synthesize and distribute N fertilizer. Other metabolic conversions in the N cycle and physical leaching processes remove N made available through N2 fixation. Thus nitrification, denitrification, and utilization of soil N by plants are processes that must be con sidered if one is to conserve N captured by N2 fixation. The meeting at Lake Tahoe united scientists from many disci plines to review the literature and to discuss current research directed toward the goal stated in the symposium title.

A Seminar held in the Framework of the Biomolecular Engineering Programma of the Commission of the European Communities, at the Carlsberg Laboratory in Copenhagen, October 9-10, 1984

During the next 30 years, farmers must produce 70% more rice than the 550 millions tons produced today to feed the increasing population. Nitrogen (N) is the nutrient that most frequently limits rice production. At current levels ofN use efficiency, we will require at least double the 10 million tons of N fertilizer that are currently used each year for rice production. Global agriculture now relies heavily on N fertilizers derived from petroleUIll, which, in turn, is vulnerable to political and economic fluctuations in the oil markets. N fertilizers, therefore, are expensive inputs, costing agriculture more than US$45 billion annually. Rice suffers from a mismatch of its N demand and N supplied as fertilizer, resulting in a 50-70% loss of applied N fertilizer. Two basic approaches may be used to solve this problem One is to regulate the timing ofN application based on needs of the plants, thus partly increasing the efficiency of the plants' use of applied N. The other is to increase the ability of the rice system to fix its own N. The latter approach is a long-term strategy, but it would have enormous environmental benefits while helping resource-poor farmers. Furthermore, farmers more easily adopt a genotype or variety with useful traits than they do crop and soil management practices that may be associated with additional costs.

Advances in Gene Technology: Molecular Genetics of Plants and Animals contains the proceedings of the Miami Winter Symposium held in January 1983 in Miami, Florida. The papers explore advances in the molecular genetics of plants and animals and cover a wide range of topics such as genetic manipulation of plants; plant cell cultures, regeneration, and somatic cell fusion; and nitrogen fixation. Practical applications of gene technology with plants are also discussed. Comprised of 84 chapters, this volume begins with an overview of how plants manufacture from carbon dioxide and water all of their substances, paying particular attention to the path of carbon in photosynthesis. The organization of the plant genome is then considered, along with techniques for cell culture, regeneration, and somatic cell fusion; vector systems; and nitrogen fixation. Some chapters focus on gene transfer by protoplast fusion; somatic cell genetic systems in corn; regulation of transcription of the nitrogen fixation operons; and leghemoglobin and nodulin genes of soybean. The final section is devoted to practical applications of gene technology to plants and to technology frontiers in animal biology, in particular embryonic development and vaccines and diagnostic methods for animal diseases. This book should be of value to molecular geneticists.