Biological Nitrogen Fixation
Tracing this source, since the emergence of life on earth, the basic roles of the two major lives of photosynthesis and nitrogen fixation have begun to support the historic mission of sustaining higher organisms. Although there are still many N mysteries here today, whether in the world of microorganisms or higher organisms, the history of the development of life is irresistible.
In the future, it has been more than one hundred years since humans really studied the mechanism of biological nitrogen fixation seriously and scientifically. Studies in the past 100 years have shown that the true nitrogen-fixing organisms are prokaryotic microorganisms, and some eukaryotic organisms (such as legumes) also fix nitrogen through prokaryotic microorganisms that have a nitrogenase system. So the so-called nitrogenases are It is a prokaryotic nitrogenase. And in the scientific community, a paradigm that has not yet been fully successful places prokaryotic nitrogenases functionally in eukaryotic cells. Therefore, the general conclusion of the scientific community is that eukaryotes cannot fix nitrogen on their own, and there is no real eukaryotic nitrogenase. That being the case, if there is only 0.01% of the hope that can prove the existence of eukaryotic nitrogenase, then let us let 99.99% of the first to study the so-called "eukaryotic nitrogenase" does not exist in the rationality. One of the reasons is that if "eukaryotic nitrogenase" already exists in the vast nature, its advantage should have been exerted and discovered by humans.
Is it true that there is absolutely no or no so-called eukaryotic nitrogenase? Or is it still not? For example, it is estimated that the earth we live in now is 46 years old (100 million years old). Before her 25 years old, organic life and life evolved. After her 25 years of age, the life of lower single cells began to flourish under the influence of photosynthetic and nitrogen fixation. When she was 40 years old, the multicellular low-plant world rose until the appearance of gymnosperms, and the entire world was “green”. The flowering plants evolved later (several million years ago), making the world we see today colorful - what a leap and feat it is. Nowadays human biological technology is changing with each passing day, and it is not unusual for some wonderful things. Although the slogan of 'conquer people' has been abandoned by human beings' own practice, the heroic spirit of 'trying to be taller than the day’s test' may still be able to 'move God.'
The beautiful, colorful and wonderful nature of the nature enjoyed by human beings is an important part of the angiosperm. It is her that the world has witnessed what is green grass and flowers. Just imagine that even if the Earth is a few years old (several million years), if the natural world really has the opportunity to develop "acquired" mutants of the original 'eukaryotic nitrogenase' like developing flowering plants, then the world will What landscapes are presented. There will still be no such miracle. Perhaps it will be necessary to wait until the '100-year-old' of the earth is at the end of its life. It will then be suspended by the universe to the wall.
Continue reading the information:
Cheng, Q.(2008) Perspectives in Biological Nitrogen Fixation Research. J. Integr. Plant Biol. 50(7), 784-796.【pdf】
Cheng, Q. Day, A, Dowson-Day, M., Shen, G.F. and Dixon, R. (2005) The Klebsiella pneumoniaenitrogenase Fe protein gene (nifH) functionally substitute for the chlL gene in Chlamydomonas reinhardtii. Biochemical and Biophysical Research Communication 329, 966-975.
Yang, J. and Cheng, Q.(2004) Origin and Evolution of the Light-Dependent Protochlorophyllide Oxidase (LPOR) Genes. Plant Biology 6 (5): 537-544. Dixon,R., Cheng,Q. Shen,G., Day,A. and Dowson-Day,M. (1997) Nif gene transfer and expression in chloroplasts: prospects and problems. Plant and Soil 194: 193-203.
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Cheng Qi, Shen Guifang (1993) Transformation and Utilization of Chloroplast Genomes. Biotechnology Bulletin 2(3), 2-3.
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The regulatory pattern of the σ54-dependent promoter responsible for the transcription of nitrogen-fixing genes was further revealed by the three-dimensional structure. Using a DNA bending protein to study the structure of the σ54-dependent promoter glnAp2 activation complex where DNA bending is involved in the activin NtrC of the AAA family, a 'sandwich' structural model of the transcriptional activation complex was proposed (see figure):
'sandwich' structural model of the transcriptional activation complex of the s54-dependent promoter glnAp2 involved in NtrC (Huo, YX, Tian, ZX, Rappas, M., Wen, J., Chen, YC, You, CH, Zhang, XD , Buck, M., Wang, YP* and Kolb, A. (2006) Protein-Induced-DNA-Bending clarifies the architectural organization of the s54-dependent glnAp2 promoter. Mol. Microbiol. 59: 168-180.)
In the natural world, certain prokaryotic microorganisms fix nitrogen in the air to ammonia through nitrogenase at room temperature and pressure. This process is called biological nitrogen fixation. Such microorganisms are called nitrogen-fixing microorganisms. It is estimated that the annual total amount of biological nitrogen fixation in the world is 200 million tons, which accounts for about three quarters of the global nitrogen requirement for crops. Under the support of the National 863 Program, the 973 Program, and the National Natural Science Foundation Project, Lin Min Laboratory, Institute of Biotechnology, Chinese Academy of Agricultural Sciences and the Pasteur Institute of France, Institute of Pathogenic Biology, Chinese Academy of Medical Sciences, Peking University and other domestic and foreign counterparts In 2005, the complete genome sequencing and functional annotation of the combined Pseudomonas stutzeri was isolated from rice rhizosphere in southern China in 2005. Pseudomonas stutzeri A1501 is currently the first to complete the whole genome sequencing in the world. Combined with Azotobacter. Comparative genomics analysis revealed that the four DNA regions in the A1501 genome have typical gene island characteristics. All the nitrogen fixation genes are clustered in a 49 kb DNA region, forming a unique “nitrogen-fixing island” that provides the evolutionary study of biological nitrogen fixation systems. A structured and functional evolutionary intermediate type. A series of new genes that may participate in bacterial nitrogen signaling or maintain optimal levels of nitrogen fixation have been identified using gene chips, timely quantitative PCR, and construction of non-polar mutant strains, laying a good foundation for further in-depth study of the joint nitrogen-fixing gene network regulation. Basic work. Through analysis and analysis of the A1501 functional genome, it is shown that the nitrogen metabolism, degradation of aromatic compounds, and PHB synthesis, as well as the resistance to glyphosate resistance, make A1501 highly resilient to changes in the soil environment and in the rhizosphere The competition is in a dominant position.