Functional difference between Sinorhizobium meliloti NifA and Enterobacter cloacae NifA.
The nifA gene is an important regulatory gene and its product, NifA protein, regulates the expression of many nif genes involved in the nitrogen fixation process. We introduced multiple copies of the constitutively expressed Sinorhizobium meliloti (Sm) or Enterobacter cloacae (Ec) nifA gene into both the nifA mutant strain SmY and the wild-type strain Sm1021. Root nodules produced by SmY containing a constitutively expressed Sm nifA gene were capable of fixing nitrogen, while nodules produced by SmY containing the Ec nifA gene remained unable to fix nitrogen, as is the case for SmY itself. However, transfer of an additional Sm nifA gene into Sm1021 improved the nitrogen-fixing efficiency of root nodules to a greater extent than that observed upon transfer of the Ec nifA gene into Sm1021. Comparative analysis of amino acid sequences between Sm NifA and Ec NifA showed that the N-terminal domain was the least similar, but this domain is indispensable for complementation of the Fix- phenotype of SmY by Sm NifA. We conclude that more than one domain is involved in determining functional differences between Sm NifA and Ec NifA.
Chengtao
Yang
Y
National Laboratory of Plant Molecular Genetics, Shanghai Institute of Plant Physiology & Ecology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China.
Guanqiao
Yu
Y
Shanjiong
Shen San Chiun Shen
SS
Jiabi
Zhu
Z
D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism*; D001483:Base Sequence; D004269:DNA, Bacterial / Q000235:genetics; D016972:Enterobacter cloacae / Q000235:genetics* / Q000378:metabolism*; D007887:Fabaceae / Q000382:microbiology; D005798:Genes, Bacterial; D005816:Genetic Complementation Test; D008969:Molecular Sequence Data; D009154:Mutation; D009586:Nitrogen Fixation; D010957:Plasmids / Q000235:genetics; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D016962:Sinorhizobium meliloti / Q000235:genetics* / Q000378:metabolism*; D013045:Species Specificity; D013559:Symbiosis; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism*
D001426:Bacterial Proteins; D004269:DNA, Bacterial; C061338:NifA protein, Bacteria; D014157:Transcription Factors