The Rhizobium leguminosarum nodulation gene nodF encodes a polypeptide similar to acyl-carrier protein and is regulated by nodD plus a factor in pea root exudate.
The DNA sequence of approximately 3.5 kb of the nodulation (nod) region of the Rhizobium leguminosarum symbiotic plasmid pRL1JI was determined. Three open reading frames were identified; genes corresponding to these have been called nodD, nodE and nodF.nodD is adjacent to nodA and is transcribed in the opposite direction. The nodF and nodE genes are downstream of, and transcribed in the same direction as, nodD with 667 nucleotides between nodD and nodF and three nucleotides separating nodF and nodE. The induction of the nodFE operon requires the nodD gene product and a component present in plant root exudate. Regions of DNA sequence preceding nodF are similar to those preceding nodA; these sequences may be involved in the regulation of the expression of nodA and nodF. Analysis of nodD revealed an amino acid sequence similar to the predicted DNA-binding domain of known DNA-binding proteins. A protein comparison of the nodF protein showed it to be similar to the acyl-carrier protein from Escherichia coli and barley, especially around the pantothenate-binding region and on this basis it is thought that this protein may be involved in an acyl transfer reaction.
Shearman
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John Innes Institute, Colney Lane, Norwich NR4 7UH, UK.
Rossen
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Johnston
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Downie
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