Zhejiang Institute of Agricultural Sciences Crop Research Institute Zhu Ganhao Institute of Cotton Research, Chinese Academy of Agricultural Sciences Wang Ruohai's new agricultural technology revolution marked by the research, development and application of genetically modified plants is being vigorously launched around the world. Genetically modified soybeans, corn, cotton and rapeseed have entered the stage of large-scale commercialization. In 1999, the area of ​​the four GM crops was 21.6 million, 11.1 million, 3.7 million and 3.4 million hm2, respectively. In terms of transgenes and traits, the largest area was herbicide-tolerant transgenic crops, followed by insect-resistant transgenic crops. So far, the main beneficiaries of GM crops such as insect-resistant and herbicide-resistant crops are growers. However, more and more cases have demonstrated that genetically modified plants can also be used to produce foods, medicines, and chemical raw materials and products that are beneficial to people's health. 1. The photosynthetic efficiency of C4 plants such as transgenic rice, corn and corn was higher than that of C3 plants such as rice and wheat. Phosphoenolpyruvate carboxylase (PEPC) plays a large role in this. The CO2 concentration in the photosynthetic system of the C4 plant increases the local CO2 concentration mechanism, making it nearly saturated even when the CO2 concentration is low, thereby greatly increasing its photosynthesis efficiency. Therefore, how to transfer this mechanism of C4 plants to C3 plants such as rice has been one of the research problems for plant biologists, but it has been proved in practice that conventional cross breeding methods are difficult to do. Recently, Ku et al. (1999) introduced the complete maize PEPC gene into the genome of C3 plant rice using Agrobacterium-mediated method. The results showed that most of the transgenic rice plants express PEPC gene at high level in corn. The content of PEPC enzyme protein in the leaves of some transgenic plants accounts for more than 12% of the total soluble protein in the leaves, and its activity is even higher than that of maize itself 2-3. Times. Northern and Southern analysis showed that there was no gene silencing of PEPC gene in transgenic rice plants. This has opened up a new path for the rapid improvement of photosynthesis efficiency of rice and other C3 crops using genetic engineering technology, and increasing the output of food crops. At present, research on transgenic plants is mostly directed to single gene control traits, but it is known that most of the traits of plants, especially crop yield and quality traits, are controlled by multiple genes. To improve these quantitative traits, it is difficult to change only one or a few of the genes, but it is necessary to simultaneously control the genetic transformation of multiple genes that control traits and even regulate genes, and make them in transgenic plants and their offspring. Stable expression and inheritance in order to achieve the desired purpose. Obviously, it is not advisable and impractical to introduce multiple coding genes and regulate genes one by one in the same way. Not long ago, Chen et al. (1998) conducted a cotransformation study on 14 foreign genes that had been integrated into different plasmids using the gene gun method, and found that 85% of R. Transgenic rice plants contain more than two exogenous genes, 17% of R. The transgenic strain contained more than 9 exogenous genes, and the most transgenic strain contained 13 exogenous genes. Most of the transgenic strains were normal in morphology, of which 63% of the transgenic strains were fertile. The overall rate of different foreign genes is basically the same, and the entire mouth is at 1-2 sites. This study laid a theoretical foundation for the improvement of quantitative traits of crops through genetic engineering. Ye et al. (2000) successfully integrated the psy, crtl, and lcy genes from other species into the rice genome using Agrobacterium-mediated methods, and made them stably expressed in the endosperm to produce enzymes necessary for vitamin A biosynthesis. Thus solved the problem that rice endosperm cannot synthesize vitamin A. For rice-based people to solve the problem of vitamin A deficiency as soon as possible shows hope. The study further shows that as long as the metabolic process of a certain substance is clearly understood, it is possible to use transgenic technology to improve it, thus providing technical support for the development of a new nutritional food crop variety. Unlike vitamins, the essential mineral nutrient elements of the body are mainly derived from the minerals that plants absorb from the soil. Therefore, the key to using genetic engineering technology to solve the problem of human mineral elements is to deeply understand the mechanism of plant absorption and storage of mineral nutrients. In fact, transgenic soybean plants that express high levels of ferritin in the endosperm have been obtained using the soybean ferritin gene and the corresponding transgenic technology (Goto et al., 1999). The question that needs to be clarified is whether the storage ferritin in this transgenic rice is absorbed by the human body (Guerinot, 2000). 2. Genetically modified soybeans DuPont, USA, has developed new soybean lines with low levels of anti-nutritional factors such as oligosaccharides, stachyose, raffinose, and galactose. In terms of improving the quality of soybean oil, they also made some new developments. The main component of soybean oil is a thermally unstable polyunsaturated fatty acid. In order to improve the thermal stability of soybean oil, the past practice was industrialized hydrogenation of soybean oil to convert polyunsaturated fatty acids into monounsaturated fatty acids. However, the consequence is to produce harmful substances that have harmful effects on the human body. The ideal way is to change the genetic composition of plants so that they can directly produce monounsaturated fatty acids. Mazur et al. (1999), through long-term unremitting efforts, obtained a new soybean line with a relative content of 85% of seed oleic acid, 3.4 times more than the original, and excellent agronomic traits. At present, this new product line has begun large-scale cultivation. Their next goal is to use the corresponding genes of Vernonia and Ricinus communis to develop a new soybean line with high content of verticillic acid (12,13-epoxyoleic acid) and ricinoleic acid, for the production of new chemical products (such as new paint curing Agents, lubricants, biodegradable plastics, etc.) At present, they have introduced the modified gene of interest into the soybean genome and expressed it in seeds. Genetically modified potato disease is a major limiting factor in potato production. Experts from the Institute of Genetic Engineering and Molecular Biology in Buenos Aires have used Agrobacterium-mediated methods to create 16 transgenic potato lines, each with 2 different antiviral, antifungal or Anti-bacterial genes, including transgenic lines against Erwinia bacterial disease, have been field tested in Chile and Brazil. In addition, a team of 13 South American and European national laboratories is working to transfer 6 antiviral, antifungal, antibacterial, herbicide-tolerant and Bt genes to the same potato variety. Another research focus of genetically modified potato is the production of edible vaccines. Arakawa et al. (1997) reported that the cholera toxin B subunit (CT-B) can be highly expressed in transgenic potato and can be folded into the native immunogenicity of this antigen in combination with GN1 gangliosides. Pentamer form. Recently, Tacket et al. (1998) conducted a human immunoassay using a transgenic potato expressing enterotoxigenic E. coli heat-labile toxin (LT). The results showed that the transgenic potato also had the expected immune effect in humans. 4. Transgenic cassava Cassava is the world's third largest source of calories after rice and corn and is one of the staple foods of African countries. At present, the production of cassava is stagnated due to the damage of fungi, bacteria and virus diseases. Ten years ago, the International Tropical Agriculture and Biotechnology Laboratory (ILTAB), the International Center for Tropical Agriculture Research (CITA) and the Cassava Biotechnology Network jointly launched the Cassava Genome Project, which aims to use molecular biology to accelerate the improvement of cassava varieties. So far, the program has mapped more than 300 molecular markers, and has used the ATB-mediated Agrobacterium-mediated system to introduce the anti-cassava mosaic virus gene and another disease-resistance gene that expresses replicase into the cassava genome. Transgenic plants. If these new lines can be applied to Daejeon production, it is expected that cassava can be increased by 10 times to 80-l00 t/hm2. The current problem is that there are fewer scientists engaged in this research and the progress is not as great as expected. 5. Genetically Modified Sweet Potatoes At the second International Conference on Agricultural Biotechnology held in 1998, Dr. Prakash, an American scientist, reported on the progress in the use of transgenic technology to improve the content and quality of sweet potato protein. After integrating artificially synthesized storage protein genes rich in essential Amino Acids into the sweetpotato genome, the two transgenic lines had a 2.5-5 fold increase in storage protein content compared to the control and a slight increase in yield. 6. Palm oil palm is mainly distributed in Malaysia, Indonesia and Central Africa. It is one of the world's major oil plants. Its oil production is 8-10 times higher than that of soybean, rapeseed, etc. Two years ago, the Malaysia Brown Research Institute (PORIM) had successfully used the gene gun method to introduce herbicide resistant genes into the palm and obtained transgenic seedlings. In May 1999, PORIM launched an investment-intensive research project aimed at improving the quality of palm oil using genetic engineering methods and enabling it to produce special products including biodegradable plastics. The current research focuses on increasing the content of oleic acid (used as cooking oil) or stearic acid (used as a substitute for cocoa butter or soap as raw material) to expand the palm oil market. However, as a perennial plant, palm has a long cycle of transgenic research. 7. Genetically Modified Bananas At present, the transgenic research of bananas is mainly focused on improving disease resistance and edible vaccines. Recently, on the basis of previous research, Belgian scientists have integrated the gene encoding Mycosphaerella fijiensis (the most serious fungal disease of banana) into the genome of bananas. It is expected that the first transgenic banana line with disease resistance will soon be bred (Moffat, 1999). In the field of edible vaccine research, the starting plants of interest were potatoes and tobacco. This was mainly due to the fact that the two solanaceous plants had relatively mature transgenic systems. However, the antigen expressed in tobacco must be refined before use. Potato tubers must be cooked before consumption. No matter if it is refined or cooked, it will destroy the antigen. Therefore, they are not ideal plants for edible vaccines. Fresh fruits and vegetables are the ideal destination plants. Bananas are the first choice because it is not only the fruit that infants and young children like, but also the staple food in many developing countries. Currently, the Boyce Thompson Institute of Botany in New York is working on the use of bananas for the production of vaccines for diarrhea and Nowalk disease.
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