Conjugational transfer of the nodulation-conferring plasmid pWZ2 in Rhizobium trifolii

Zurkowski, W

doi:10.1007/bf00428746

Cited by 12 publications

(9 citation statements)

References 7 publications

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“…This phenomenon indirectly suggests that R. trifolii nodulation is plasmid controlled. This has been confirmed in further physicochemical and genetic studies (7,20,21,24). The molecular mechanism eliminating the nodulation properties of R. trifolii is presented here.…”

supporting

confidence: 68%

“…Effect of P-class plasmids on stabilization of nodulation properties of R. trifoiji. P-class plasmids were introduced to R. trifolii from Pseudomonas aeruginosa by conjugation, using a crossing method on membrane filters (Millipore Corp.) described previously (21). I found that after the introduction of the P-class plasmid RP4 or R68.45 to R. trifolii, the nodulation properties of the strains at elevated temperatures became stable.…”

Section: Resultsmentioning

confidence: 99%

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Molecular mechanism for loss of nodulation properties of Rhizobium trifolii

Zurkowski¹

1982

J Bacteriol

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Of 18 Rhizobium trifolii strains tested, 12 showed a high frequency of loss of nodulation ability after incubation in cultures at elevated temperatures. A correlation between loss of nodulation ability and loss of a large plasmid was demonstrated for R. trifolii. In some nonnodulating (Nod-) mutants, deletions occurred instead of total elimination of the plasmid molecule. The maximum curing effect was observed in bacteria incubated at 35 degrees C. After 4 or more days of incubation at this temperature, the viability of bacteria decreased markedly, and the number of nonnodulating mutants increased significantly. At the elevated temperature DNA synthesis was stopped completely after 2 h, whereas protein synthesis proceeded for a few days. Microscopic observations showed that during the first 3 days of incubation at the elevated temperature, the bacterial cells increased markedly in size. These large irregular cells then divided and produced Nod- clones. Nonnodulating clones did not result from the selection of temperature-resistant mutants. The presence of P-group plasmids in Rhizobium strains strongly inhibited the loss of nodulation ability during incubation at 35 degrees C. The observed phenomenon did not result from integrative suppression. It is possible that a product(s) of the genes of R-plasmids acts as a stabilizing agent on the replication process of the indigenous Rhizobium plasmids.

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supporting

confidence: 68%

Section: Resultsmentioning

confidence: 99%

Molecular mechanism for loss of nodulation properties of Rhizobium trifolii

Zurkowski¹

1982

J Bacteriol

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“…The homologous region of nifDNA between species, however, is only about 1.5 kb (31). Nodulation ability is encoded on pJB5JI (18) and has been reported to be plasmid encoded in R. trifolii (17,41). Results reported here suggest that genes essential for nodulation in R. trifolii T37 are coded for on pRtT37a.…”

Section: Discussionmentioning

confidence: 64%

Identification of a Rhizobium trifolii plasmid coding for nitrogen fixation and nodulation genes and its interaction with pJB5JI, a Rhizobium leguminosarum plasmid

Christensen¹,

Schubert²

1983

J Bacteriol

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Rhizobium trifolii T37 contains at least three plasmids with sizes of >250 megadaltons. Southern blots of agarose gels of these plasmids probed with Rhizobium meliloti nif DNA indicated that the smallest plasmid, pRtT37a, contains the nifgenes. Transfer of the Rhizobium leguminosarum plasmid pJB5JI, which codes for pea nodulation and the nif genes and is genetically marked with Tn5, into R. trifolii T37 generated transconjugants containing a variety of plasmid profiles. The plasmid profiles and symbiotic properties of all of the transconjugants were stably maintained even after reisolation from nodules. The transconjugant strains were placed into three groups based on their plasmid profiles and symbiotic properties. The first group harbored a plasmid similar in size to pJB5JI (130 megadaltons) and lacked a plasmid corresponding to pRtT37a. These strains formed effective nodules on peas but were unable to nodulate clover and lacked the R. trifolii nifgenes. This suggests that genes essential for clover nodulation as well as the R. trifolii nifgenes are located on pRtT37a and have been deleted. The second group harbored hybrid plasmids formed from pRtT37a and pJB5JI which ranged in size from 140 to ca. 250 megadaltons. These transconjugants had lost the R. leguminosarum nif genes but retained the R. trifolii nif genes. Strains in this group nodulated both peas and clover but formed effective nodules only on clover. The third group of transconjugants contained a hybrid plasmid similar in size to pRtT37b. These strains contained the R. trifolii and R. leguminosarum nif genes and formed N2-fixing nodules on both peas and clover.

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“…Note binding of trifoliin A-gold colloid to the entire cell in A (32,000 x ) and its higher magnification in B. 88,000 x 1979; Prakash et al, 1980;Zurkowski, 1980Zurkowski, , 1981Zurkowski, , 1982Hooykaas et at., 1981 ;Rosenberg, Boistard, Denarie & Casse-Delbart, 1981;Bafalvi etal., 1981). For instance, the genes responsible for the 2-deoxy-D-glucose inhibitable attachment of R. trifolii to clover root hairs are encoded on the large nodulation plasmid designated pWZ2 (Zurkoski, 1980), and incorporation of the trifoliin A binding sugar, quinovosamine into the LPS of R. triJ'olii is controlled by the clover nodulation plasmid (Russa, Urbanik, Kowalczuk, & Lorkiwicz, 1982).…”

Section: Host-specificity Genes Are Plasmid Encodedmentioning

confidence: 99%