of gene transfer between micro-organisms and plants
and objectives (1)
The intentional release of genetically modified organisms (GMOs) into
the environment has led to increased interest in possible interactions
that may occur between resident organisms. Of particular interest is the
potential of introduced genetic material to transfer, stably integrate
into and be expressed in resident species. This raises issues of the potential
ramifications on the environment and human health. Classical microbial
genetic studies carried out under laboratory conditions have identified
a number of mechanisms whereby genetic information can be transferred
and established in closely related, recipient species. 'Trans-kingdom'
gene transfer from bacteria to eukaryotes has also been demonstrated in
In the absence
of documented proof of genetic transfer from plants to bacteria, our aims
were to construct transgenic plants expressing foreign DNA
and assess possible gene transfer between plants and micro-organisms.
(1) This project was a direct follow-on from EC project:
Approach and methodology
It is unknown whether genetic transfer from plants to bacteria occurs
under natural conditions, so several different environments were used
in the consortium to look for evidence of gene transfer. These included
a tobacco plant tumour, field conditions, conventional bacterial growth
media, and in laboratory microcosms designed to mimic and allow experimental
manipulation of the physiochemical characteristics of the soil. In Bielefeld
we analysed transgenic plants containing the aacC1 gene conferring
resistance against gentamicine to bacteria and the luciferase gene conferring
bioluminescence to plants and bacteria. Transfer of these genes to bacteria
was detected by selecting on antibiotica-containing media and via tests
for bioluminescence. We used the soil bacterium Agrobacterium tumefaciens
as a biological tool to detect plant-bacterium DNA transfer since this
bacterium is well known to be the biological agent of the crown gall disease
which is caused by the transfer of a couple of bacterial genes into plant
cells. The mechanisms of this transformation via DNA transfer obviously
make A. tumefaciens a good candidate for the investigation of the
DNA transfer from the plant to bacteria. In addition, conventional transformation
assays were carried out with Agrobacterium tumefaciens and plasmid
DNA carrying the aacC1 gene to test the influence of several factors
typical for Agrobacterium-driven plant transformation, e.g. acetosyringon
(induction of the bacterial vir genes), linear or single-stranded
plasmid DNA, and plant tissue homogenates.
Main findings and outcome
No evidence for gene transfer from plants to bacteria (A. tumefaciens)
in a plant tumour was obtained. Control experiments ensured that the genes
under investigation were active in bacteria if transfer would have occurred.
These studies have provided us with a better understanding of the DNA
plasmid transfer. The finding that sequences of plant origin were not
transferred to a significant frequency clearly demonstrated that natural
gene transfer from plant to A. tumefaciens is rather unlikely notwithstanding
the sophisticated mechanisms allowing this bacterium to transfer DNA to
the plant efficiently.
Gascon J., Oubina A., Perez-Lezaun A., Urmeneta J., Sensitivity
of selected bacterial species to UV-radiation.
Curr. Microbiol., 30 (3), 1995, pp. 177-182.
Lafuente R., Maymo-Gatell X., Mas-Castella J., Guerrero R., Influence
of environmental factors on plasmid transfer in soil microcosms.
Curr. Microbiol., 32 (4), 1996, pp. 213-220.
Paget E., Simonet P., On the track of natural transformation
in soil, FEMS.
Microbiol. Ecol., 15 (1-2), 1994, pp. 109-117.
October 1991 March 1994
Universidad de Barcelona (ES)
Universität Bielefeld (DE)
Université de Lyon
Aristotle University of Thessaloniki (GR)