Abstract
Little is known about the effect of the host on the genetic stability of bacterial plant pathogens. Crown gall, a plant disease caused by Agrobacterium tumefaciens, may represent a useful model to study this effect. Indeed, our previous observations on the natural occurrence and origin of nonpathogenic agrobacteria suggest that the host plant might induce loss of pathogenicity in populations of A. tumefaciens. Here we report that five different A. tumefaciens strains initially isolated from apple tumors produced up to 99% nonpathogenic mutants following their reintroduction into axenic apple plants. Two of these five strains were also found to produce mutants on pear and/or blackberry plants. Generally, the mutants of the apple isolate D10B/87 were altered in the tumor-inducing plasmid, harboring either deletions in this plasmid or point mutations in the regulatory virulence gene virG. Most of the mutants originating from the same tumor appeared to be of clonal origin, implying that the host plants influenced agrobacterial populations by favoring growth of nonpathogenic mutants over that of wild-type cells. This hypothesis was confirmed by coinoculation of apple rootstocks with strain D10B/87 and a nonpathogenic mutant.
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- Ankenbauer R. G., Best E. A., Palanca C. A., Nester E. W. Mutants of the Agrobacterium tumefaciens virA gene exhibiting acetosyringone-independent expression of the vir regulon. Mol Plant Microbe Interact. 1991 Jul-Aug;4(4):400–406. doi: 10.1094/mpmi-4-400. [DOI] [PubMed] [Google Scholar]
- Citovsky V., Zambryski P. Transport of nucleic acids through membrane channels: snaking through small holes. Annu Rev Microbiol. 1993;47:167–197. doi: 10.1146/annurev.mi.47.100193.001123. [DOI] [PubMed] [Google Scholar]
- Fortin C., Marquis C., Nester E. W., Dion P. Dynamic structure of Agrobacterium tumefaciens Ti plasmids. J Bacteriol. 1993 Aug;175(15):4790–4799. doi: 10.1128/jb.175.15.4790-4799.1993. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Fortin C., Nester E. W., Dion P. Growth inhibition and loss of virulence in cultures of Agrobacterium tumefaciens treated with acetosyringone. J Bacteriol. 1992 Sep;174(17):5676–5685. doi: 10.1128/jb.174.17.5676-5685.1992. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Hayman G. T., Farrand S. K. Characterization and mapping of the agrocinopine-agrocin 84 locus on the nopaline Ti plasmid pTiC58. J Bacteriol. 1988 Apr;170(4):1759–1767. doi: 10.1128/jb.170.4.1759-1767.1988. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Huang M. L., Cangelosi G. A., Halperin W., Nester E. W. A chromosomal Agrobacterium tumefaciens gene required for effective plant signal transduction. J Bacteriol. 1990 Apr;172(4):1814–1822. doi: 10.1128/jb.172.4.1814-1822.1990. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Nautiyal C. S., Dion P. Characterization of the Opine-Utilizing Microflora Associated with Samples of Soil and Plants. Appl Environ Microbiol. 1990 Aug;56(8):2576–2579. doi: 10.1128/aem.56.8.2576-2579.1990. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Powell B. S., Powell G. K., Morris R. O., Rogowsky P. M., Kado C. I. Nucleotide sequence of the virG locus of the Agrobacterium tumefaciens plasmid pTiC58. Mol Microbiol. 1987 Nov;1(3):309–316. doi: 10.1111/j.1365-2958.1987.tb01937.x. [DOI] [PubMed] [Google Scholar]
- Rodenburg K. W., Scheeren-Groot E., Vriend G., Hooykaas P. J. The N-terminal domain of VirG of Agrobacterium tumefaciens: modelling and analysis of mutant phenotypes. Protein Eng. 1994 Jul;7(7):905–909. doi: 10.1093/protein/7.7.905. [DOI] [PubMed] [Google Scholar]
- Rogowsky P. M., Powell B. S., Shirasu K., Lin T. S., Morel P., Zyprian E. M., Steck T. R., Kado C. I. Molecular characterization of the vir regulon of Agrobacterium tumefaciens: complete nucleotide sequence and gene organization of the 28.63-kbp regulon cloned as a single unit. Plasmid. 1990 Mar;23(2):85–106. doi: 10.1016/0147-619x(90)90028-b. [DOI] [PubMed] [Google Scholar]
- Scheeren-Groot E. P., Rodenburg K. W., den Dulk-Ras A., Turk S. C., Hooykaas P. J. Mutational analysis of the transcriptional activator VirG of Agrobacterium tumefaciens. J Bacteriol. 1994 Nov;176(21):6418–6426. doi: 10.1128/jb.176.21.6418-6426.1994. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Winans S. C. Two-way chemical signaling in Agrobacterium-plant interactions. Microbiol Rev. 1992 Mar;56(1):12–31. doi: 10.1128/mr.56.1.12-31.1992. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Youderian P., Bouvier S., Susskind M. M. Sequence determinants of promoter activity. Cell. 1982 Oct;30(3):843–853. doi: 10.1016/0092-8674(82)90289-6. [DOI] [PubMed] [Google Scholar]
- Young J. P., Downer H. L., Eardly B. D. Phylogeny of the phototrophic rhizobium strain BTAi1 by polymerase chain reaction-based sequencing of a 16S rRNA gene segment. J Bacteriol. 1991 Apr;173(7):2271–2277. doi: 10.1128/jb.173.7.2271-2277.1991. [DOI] [PMC free article] [PubMed] [Google Scholar]