Rice genome is the most complete gene sequencing in higher organisms. Among the 37,500 genes identified by scientists, several genes affect the future of important agricultural products. For example, genes that increase rice yield and genes that change rice photoperiod. Some commercial grain farms in the southern United States use dry land direct seeding technology to grow rice, which avoids paddy field cultivation, seedling raising and transplanting, and its production technology is not much different from that of planting wheat. Drain the ground before sowing. There are direct seeding rice seeds.
In 1950s, direct seeding of rice was widely spread in the north of China, accounting for 70% before 1960s in Heilongjiang province, and was also used in the south in 1960s. With the development of economy, a large number of rural young and middle-aged laborers have entered the urban labor market, the rural labor force has decreased, chemical herbicides have been widely used, and direct seeding rice cultivation has shown a rapid development trend.
The agricultural machinery department of Yizheng City, Jiangsu Province successfully demonstrated a new rice transplanting technology-mechanized dry land direct seeding of rice in Puxi Town. Compared with the traditional rice transplanting method, this technology saves the link of rice seedling raising and sowing, and the rice seeds are directly sown with a drill after soaking and germination, which has the advantages of saving labor, saving cost and increasing efficiency. According to estimates, a drill can sow 30 mu per day, saving about 200 yuan per mu compared with traditional planting methods.
Some people may think that direct seeding rice is a new technology that has not been developed for a long time, but I don't know that direct seeding cultivation of rice has existed since ancient times, even before transplanting, that is, direct seeding first and then transplanting. Scientists have successfully obtained nearly 2,000 rice cDNA fragments by using original gene isolation technology, and developed the first rice gene chip with unique functions in China.
This modular expression sequence tagging technology (M-EST) was first proposed by the research team of Professor Li Debao from Institute of Biotechnology, Zhejiang University, and has been patented in China National Intellectual Property Administration, China.
Thousands of densely arranged molecular microarrays integrated on the chip enable people to analyze a large number of biomolecules in a short time and obtain biological information in samples quickly and accurately, and the efficiency is hundreds of times that of traditional detection methods. It is praised by some scientists as another far-reaching scientific and technological revolution after large-scale integrated circuits.
The research team led by researcher Lin Hongxuan from Institute of Plant Physiology and Ecology, Shanghai Institute of Life Sciences, Chinese Academy of Sciences, and State Key Laboratory of Plant Molecular Genetics made a breakthrough in the research of rice yield-related functional genes, successfully cloned the quantitative trait gene GW2 for controlling rice grain weight, and elaborated the related biological functions and mechanisms, indicating that the gene has broad application prospects in high-yield molecular breeding.
Genetic improvement or genetic engineering is one of the effective means to increase crop yield. Searching for functional genes related to high yield has important theoretical significance and application value for high yield breeding of rice. Grain weight is one of the factors that determine rice yield. It is a complex quantitative trait controlled by multiple genes, and the genetic regulation mechanism of related molecules is still unclear.
Researcher Lin Hongxuan directed doctoral students Song Xianjun and Huang Wei to successfully clone the quantitative trait gene GW2 for controlling rice grain weight after years of painstaking research. A large number of detailed experimental results show that GW2, as a new E3 ubiquitin ligase, may participate in the degradation of protein, which promotes cell division, thus regulating the size of rice husk and controlling grain weight and yield. When the function of GW2 is lost or reduced, the ability of gene to degrade protein related to cell division will decrease, which will accelerate cell division and increase the number of cells in rice husk, thus significantly increasing the width of rice grain, accelerating grain filling and increasing grain weight and yield.
Researchers introduced GW2 gene of large-grain varieties into small-grain varieties to cultivate new strains by molecular marker selection, and harvested 25 plants planted in the field respectively. Measure the yield of each plant. Compared with small grain varieties, although the number of grains per panicle of the new strain decreased, the yield per plant increased significantly due to the obvious increase of grain weight, which indicated that the gene was valuable in high-yield breeding. The effect of increasing production needs to be further investigated and verified by plot test. The research results provide new genes with independent intellectual property rights and important application prospects for crop high-yield breeding; A new viewpoint is put forward to clarify the molecular genetic regulation mechanism of crop yield and seed development.
2007-04-09 Three reviewers of Nature Genetics unanimously spoke highly of this research: "We can now obtain rice grains with appropriate size by controlling the function of GW2, which I think is of great significance in the history of rice yield breeding." "The cloning, sequence analysis, transgenic phenotype identification and functional experiment of E3 ubiquitin ligase are convincing" and "This is a masterpiece that will arouse great interest of geneticists. In this paper, a large number of in-depth experiments, including gene cloning, gene structure analysis, function and phenotype identification, proved that the gene controls the grain size of rice and put forward valuable insights for the study of genetic regulation mechanism of crop seeds. " Demographic analysis of single nucleotide polymorphisms (SNPs) from 630 gene fragments showed the single domestication origin of rice. On the other hand, the population genetic analysis of the whole genome data of cultivated rice and wild rice often shows that the genomes of indica rice and japonica rice generally seem to originate independently, but many genome fragments with domesticated alleles may originate only once. Despite these advances, more extensive sampling and population genome sequencing are needed to further clarify the evolutionary history of rice domestication. In-depth study of haplotype structure near domestication site will play an important role in evaluating the direction of gene infiltration.
In this paper, the researchers obtained genome sequences from 446 common wild rice and 1 0,083 cultivated indica and japonica rice varieties with different geographical locations, and constructed a comprehensive rice genome variation map. In the process of searching for selective markers, the researchers identified 55 selective scans that occurred during domestication. The in-depth analysis of domestication and genome-wide pattern reveals that japonica rice was first domesticated from a special common wild rice in the middle reaches of the Pearl River in South China, and indica rice was later formed by crossing japonica rice with local wild rice and spread to Southeast Asia and South Asia as the original cultivated species. These domestication-related traits were analyzed by high-resolution genetic map.