Scientists of Monsanto Company in the United States used the method of introducing genes to make it impossible to produce ACC synthase, and of course, it was impossible to form ACC. Finally, without ACC, ethylene cannot be formed. In this way, the ethylene synthesis of transgenic tomato was inhibited by 99.5%, and the natural fruit could not be softened. Only when treated with ethylene can the fruit turn red and soft, showing natural color and flavor.
Secondly, another important factor affecting the ripening and softening of tomato fruit is the hardness of its cell wall. Cell wall is composed of pectin, cellulose and hemicellulose, among which one of the important components of pectin is polygalacturonic acid (PG for short), and the enzyme that can decompose PG is called PG enzyme. After tomato fruit ripens, there are more and more PG enzymes, so PG is decomposed and becomes less and less, and the fruit becomes softer and softer.
Therefore, only by finding a way to turn off the gene that gives instructions to PG enzyme and block the production of PG enzyme, so that PG will not be decomposed, the fruit will not become soft. Scientists from Kyle Gene Company in the United States have cultivated transgenic tomatoes in this way. Compared with ordinary tomato, the growth time is prolonged by one week, which can make the sugar and acid necessary for tomato fruit growth. The company has sold this tomato to retailers, which is the first time that genetically modified food has been approved in the United States.
During the period of 1995, Luo Yunbo, a scientist of Beijing Agricultural University, cultivated tomatoes that blocked ethylene synthesis through genetic engineering, and the fruits showed strong storability.
From 65438 to 0996, Professor Ye Zhibiao of Huazhong Agricultural University in China used transgenic technology to block ethylene synthesis, which also achieved the purpose of tomato storage and preservation. The storability (60 ~ 80 days) of the two excellent varieties was significantly higher than that of the original tomato parents, and the hardness and color of the original parents' fruits were maintained.
Don't underestimate this "special" tomato. In the past, the rot rate of tomatoes in China was as high as 50% every year. The transgenic storage-resistant tomatoes can be preserved for a long time after picking, and the annual loss can be recovered only in Xinjiang, with remarkable economic benefits.
Although there are not many pests on tomatoes, they sometimes affect the yield. 1994, Liang Xiaoyou and others introduced genes resistant to cucumber mosaic virus and tobacco budworm into tomatoes to obtain transgenic tomatoes with double resistance. This shows a bright prospect for the genetic engineering research of comprehensive resistant plants.
With the development of plant transgenic technology, people can change the characteristics of plants according to their own needs. For example, in recent years, scientists have discovered antifreeze proteins and antifreeze protein genes, which provide new weapons for cultivating antifreeze plants. If the antifreeze protein gene is introduced into plant cells, can it also obtain antifreeze characteristics?
The research team led by Huang from the Biology Department of Harbin Normal University wrote a new song about genetically modified tomatoes-let fish and tomatoes "get married".
They found that the "American butterfly" living in cold water in the cold temperate zone has a lot of antifreeze proteins. Why not use transgenic technology to transfer the antifreeze gene of "American Butterfly" into tomatoes and cultivate cold-resistant tomato varieties to alleviate the vegetable basket problem in Harbin in autumn and winter? So they began to study the tomato transgenic work of 1990.
First, they extracted antifreeze protein genes from American butterflies and injected antifreeze genes into pollen tubes when tomatoes bloomed, thus obtaining tomato seeds. After 6 years of continuous screening and cultivation, the first transgenic cold-resistant tomato in China was finally obtained.
These tomatoes show good cold resistance. After autumn, the land in Harbin turned yellow. Only the leaves in the transgenic tomato field were green and red. The harvest period could be extended by one month, and the yield was more than twice that of ordinary tomatoes. Its taste is the same as that of tomatoes we usually eat, and it has no fishy smell.
However, due to the consideration of human health and the limited level of understanding, people still hold a wait-and-see attitude towards genetically modified products. In fact, these genetically modified foods are no different from ordinary foods.
Since the emergence of agriculture, farmers have been changing the genes of plants. There is not much difference between traditional plant cultivation and genetic engineering, but the former changes slowly, while the latter changes quickly and can be effective in a short time. The final result of both is to readjust plant genes, break down barriers between species, enable plants and animals to "marry" and make plant cells contain animal genes.
The chairman of China Agricultural Biotechnology Society said: "We should not only restrain the research of biotechnology, speed up the development of high technology, and strive to occupy a certain market share of biotechnology, but also be cautious about safety issues and be responsible for human health and ecological environment protection."
Professor Ye Zhibiao, who presided over the transgenic storage-resistant tomatoes, said: "Our transgenic tomatoes have been sold on the campus of Huazhong University of Science and Technology, and teachers and students have no different feelings when buying them."
At the end of 1993, China Science and Technology Commission promulgated the Measures for the Administration of Genetic Engineering; 65438-0996 The Ministry of Agriculture issued the Implementation Measures for Safety Management of Agricultural Biogenetic Engineering. On June 2nd, 1997, the Ministry of Agriculture approved the commercial production of transgenic tomatoes successfully researched by Professor Ye Zhibiao.
1995, the United States approved the introduction of antiviral genes into the pumpkin market.
Of course, citizens in some countries do not accept genetically modified foods. For example,1April 1997, Austria had12.67 million signatures, demanding that the sale of genetically modified foods be banned in its country.
Young friends! Maybe you will think of more and better ways to change biological characteristics, create new varieties that better meet people's needs, and make our life better. We look forward to this day coming soon!