Agrobacterium tumefaciens Mediated Gene Transfer
Image Permission Pending from International Society
for Microbial Ecology
What is Agrobacterium tumefaciens?
Ø Bacterial plant pathogen
found in the soil that results in tumorous growths and/or roots to develop in
infected plants (“Agrobacterium tumefaciens”
2001)
Ø This infection is known as Crown Gall Disease
(Deacon 2002)
Ø The bacteria transfers a
tumor-inducing (Ti) plasmid located in a section of its DNA (known as T-DNA)
into the nucleus of an infected plant cell (“Bye Bye
Butterfly? BT Corn & Its
Implications” 2000)
Ø The newly introduced
Ti-plasmid is incorporated into the plant genome and is consequently
transcribed (Sforza 2002)
Ø The T-DNA that is integrated
into the plant genome contains cancer-causing oncogenic genes and genes that
synthesize opines which are excreted by infected Crown Gall cells and are a
food source for Agrobacterium tumefaciens (González-Cabrera
1998)
Agrobacterium tumefaciens Infection
& Gene Transfer
Figure
1. Basic steps in transformation of
plant cells by Agrobacterium tumefaciens. The T-DNA transfer is
represented according to updated knowledge on this process, although many of
involved mechanisms have not been elucidated yet and the experimental results
only allow hypotheses about it. Entering of T-DNA complex into the plant cell
is almost completely uncharacterized and experimentally only the VirB7-VirB9
disulphide bound heterodimmers have been evidenced. The most important events
are briefly mentioned in chronological order (
Image/Caption Permission Pending from Electronic Journal of
Biotechnology
Importance to Biotechnology &
Genetically Modified Organisms
Ø Oncogenes and opine-creating
genes can be removed from the Ti-Plasmid that is transferred to the plant cell
by T-DNA (“Mercenary Microbes” 2002)
Ø Scientists can insert any
gene they want into the plasmid in place of the tumor causing genes and
subsequently into the plant cell genome (“Mercenary Microbes” 2002)
Ø Original problems existed in
that Agrobacterium tumefaciens only
affects dicotyledonous plants (“Bye Bye Butterfly? BT Corn & Its Implications” 2000)
Ø Monocotyledon plants like
corn are not very susceptible to the bacterial infection (“Bye Bye Butterfly? BT
Corn & Its Implications” 2000)
Ø By varying experimental
materials, culture conditions, bacterial strains, etc. scientists have successfully
used A. tumefaciens Gene Transfer to
produce BT
Corn (“Bye Bye Butterfly? BT Corn & Its Implications” 2000)
Ø This method of gene transfer
enables large DNA strands to be transferred into the plant cell without risk of
rearrangement whereas other methods like the Gene Gun have trouble doing this (“Bye
Bye Butterfly?
BT Corn & Its Implications” 2000)
Ø The vast majority of
approved genetically engineered agriculture has been transformed by means of Agrobacterium tumefaciens Mediated Gene
Transfer (Hemmer 2002)
BT Corn Produced by Agrobacterium tumefaciens Mediated Gene
Transfer
Image Permission Granted by University
of Toronto - Zoology
Agrobacterium
tumefaciens Mediated Gene Transfer Links
1) Pathogenesis of Crown
Gall Disease – Excellent 3D images and videos of Agrobacterium tumefaciens gene transfer
2) International Society
for Microbial Ecology – Good information on Agrobacterium
tumefaciens…”Microbe
of the Month”
3) The Microbial World –
Biology and Control of Crown Gall – Excellent webpage discussing Crown Gall
Disease
4) Genome Link - Agrobacterium tumefaciens – General
information as well as many links and databases
5) Electronic Journal of
Biotechnology – Excellent review article on “The Agrobacterium tumefaciens gene transfer to plant cell”
6) Transgenic Plant
Transformation Methods – Discusses use of A. tumefaciens gene transfer and prevalence of method usage
7) BT
Corn Production Using Agrobacterium Gene
Transfer – Great webpage on the creation of BT Corn using Agrobacterium
References
“Agrobacterium tumefaciens.”
“Bye
Bye Butterfly? BT Corn & Its
Implications.” 2000.
Deacon,
Jim. “Biology and Control of Crown Gall
(Agrobacterium tumefaciens).”
González-Cabrera,
Joel, et. al. “The Agrobacterium tumefaciens gene transfer to plant cell.” 1998.
Electronic Journal of Biotechnology.
Hemmer,
Wolfram. “Foods Derived from Genetically
Modified Organisms and Detection Methods.”
Zentrum BATS.
“Mercenary
Microbes.” International Society for
Microbial Ecology at
Sforza,
Peter, et. al. “Pathogenesis of Crown
Gall.” Virginia Tech – Department of
Plant Pathology, Physiology, & Weed Science.
This webpage was
created by David Shelburne ’04 as an assignment for an undergraduate course—Bio
361: Genetically Modified Organisms—at
© Copyright 2002 Department of Biology,
Send comments, questions,
and suggestions to: dashelburne@davidson.edu