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Functional difference between Sinorhizobium meliloti NifA and Enterobacter cloacae NifA
Yang Chengtao1, Yu Guanqiao, Shen San Chiun Shen Shanjiong
1National Laboratory of Plant Molecular Genetics, Shanghai Institute of Plant Physiology & Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China.
Science in China. Series C, Life Sciences
|September 24, 2004
Summary
The Sinorhizobium meliloti nifA gene restored nitrogen fixation in mutant strains, unlike the Enterobacter cloacae nifA gene. Functional differences between these nifA genes, particularly in the N-terminal domain, impact nitrogen fixation efficiency.
Area of Science:
- Microbiology
- Molecular Biology
- Plant-Microbe Interactions
Background:
- The nifA gene and its NifA protein product are crucial regulators of nitrogen fixation genes.
- Understanding variations in nifA gene function across different bacterial species is important for optimizing nitrogen fixation.
Purpose of the Study:
- To investigate the functional differences between Sinorhizobium meliloti (Sm) and Enterobacter cloacae (Ec) nifA genes.
- To determine the role of specific NifA protein domains in nitrogen fixation complementation.
Main Methods:
- Introduction of constitutively expressed Sm and Ec nifA genes into nifA mutant (SmY) and wild-type (Sm1021) Sinorhizobium meliloti strains.
- Assessment of nitrogen-fixing capability in root nodules formed by these modified strains.
- Comparative amino acid sequence analysis of Sm NifA and Ec NifA proteins.
Main Results:
- The Sm nifA gene restored nitrogen fixation in the SmY mutant, while the Ec nifA gene did not.
- Transferring an additional Sm nifA gene into the wild-type Sm1021 enhanced nitrogen-fixing efficiency more than transferring the Ec nifA gene.
- The N-terminal domain, despite being the least similar between Sm NifA and Ec NifA, is essential for Sm NifA's complementation of the Fix- phenotype.
Conclusions:
- Functional differences exist between Sm NifA and Ec NifA, influencing nitrogen fixation.
- Multiple domains within the NifA protein contribute to these functional variations.