ISSN:
1617-4623
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Summary R-prime plasmids carrying 100–200 kb regions of R. meliloti DNA coding for symbiotic functions were isolated from a Km8 derivative of R68.45. The R-primes were obtained from matings between R. meliloti strains containing Tn5-induced symbiotic mutations and E. coli recipients by selecting for the kanamycin resistance marker of Tn5. It was demonstrated that the regions inserted into the R-primes were identical with those DNA segments where Tn5 was located in the respective parental R. meliloti. R-primes were generated from both the R. meliloti chromosome and from the megaplasmid pRme41b. A set of R-primes, carrying the nitrogen fixation (nif) gene cluster, also carried genes required for nodulation (nod genes) of alfalfa. Transfer of these R-primes into different Nod- mutants restored the Nod+ phenotype. When they were introduced into A. tumefaciens the transconjugants formed small nodules on alfalfa. This indicates that nodulation and nitrogen fixation genes of the R. meliloti megaplasmid are clustered on a relatively short DNA segment.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00326065
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