Abstract
The occurrence in Azospirillum brasilense of genes that code for exopolysaccharide (EPS) synthesis was investigated through complementation studies of Rhizobium meliloti Exo- mutants. These mutants are deficient in the synthesis of the major acidic EPS of Rhizobium species and form empty, non-nitrogen-fixing root nodules on alfalfa (J. A. Leigh, E. R. Signer, and G. C. Walker, Proc. Natl. Acad. Sci. USA 82:6231-6235, 1985). We demonstrated that the exoC mutation of R. meliloti could be corrected for EPS production by several cosmid clones of a clone bank of A. brasilense ATCC 29145. However, the EPS produced differed in structure from the wild-type R. meliloti EPS, and the symbiotic deficiency of the exoC mutation was not reversed by any of these cosmid clones. The exoB mutation could be corrected not only for EPS production but also for the ability to form nitrogen-fixing nodules on alfalfa by one particular cosmid clone of A. brasilense. Tn5 insertions in the cloned DNA were isolated and used to construct Azospirillum mutants with mutations in the corresponding loci by marker exchange. It was found that these mutants failed to produce the wild-type high-molecular-weight EPS, but instead produced EPSs of lower molecular weight.
Full text
PDF
Images in this article
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Bánfalvi Z., Sakanyan V., Koncz C., Kiss A., Dusha I., Kondorosi A. Location of nodulation and nitrogen fixation genes on a high molecular weight plasmid of R. meliloti. Mol Gen Genet. 1981;184(2):318–325. doi: 10.1007/BF00272925. [DOI] [PubMed] [Google Scholar]
- Cangelosi G. A., Hung L., Puvanesarajah V., Stacey G., Ozga D. A., Leigh J. A., Nester E. W. Common loci for Agrobacterium tumefaciens and Rhizobium meliloti exopolysaccharide synthesis and their roles in plant interactions. J Bacteriol. 1987 May;169(5):2086–2091. doi: 10.1128/jb.169.5.2086-2091.1987. [DOI] [PMC free article] [PubMed] [Google Scholar]
- De Vos G. F., Walker G. C., Signer E. R. Genetic manipulations in Rhizobium meliloti utilizing two new transposon Tn5 derivatives. Mol Gen Genet. 1986 Sep;204(3):485–491. doi: 10.1007/BF00331029. [DOI] [PubMed] [Google Scholar]
- Douglas C. J., Halperin W., Nester E. W. Agrobacterium tumefaciens mutants affected in attachment to plant cells. J Bacteriol. 1982 Dec;152(3):1265–1275. doi: 10.1128/jb.152.3.1265-1275.1982. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Douglas C. J., Staneloni R. J., Rubin R. A., Nester E. W. Identification and genetic analysis of an Agrobacterium tumefaciens chromosomal virulence region. J Bacteriol. 1985 Mar;161(3):850–860. doi: 10.1128/jb.161.3.850-860.1985. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Dylan T., Ielpi L., Stanfield S., Kashyap L., Douglas C., Yanofsky M., Nester E., Helinski D. R., Ditta G. Rhizobium meliloti genes required for nodule development are related to chromosomal virulence genes in Agrobacterium tumefaciens. Proc Natl Acad Sci U S A. 1986 Jun;83(12):4403–4407. doi: 10.1073/pnas.83.12.4403. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Friedman A. M., Long S. R., Brown S. E., Buikema W. J., Ausubel F. M. Construction of a broad host range cosmid cloning vector and its use in the genetic analysis of Rhizobium mutants. Gene. 1982 Jun;18(3):289–296. doi: 10.1016/0378-1119(82)90167-6. [DOI] [PubMed] [Google Scholar]
- Leigh J. A., Signer E. R., Walker G. C. Exopolysaccharide-deficient mutants of Rhizobium meliloti that form ineffective nodules. Proc Natl Acad Sci U S A. 1985 Sep;82(18):6231–6235. doi: 10.1073/pnas.82.18.6231. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Rosenberg C., Boistard P., Dénarié J., Casse-Delbart F. Genes controlling early and late functions in symbiosis are located on a megaplasmid in Rhizobium meliloti. Mol Gen Genet. 1981;184(2):326–333. doi: 10.1007/BF00272926. [DOI] [PubMed] [Google Scholar]