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 (boxes 1 through 13). Each step is described in the text.

 

 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.”  06 October 2001.  GenomeLink.org.  01 September 2002.  <http://www.genomelink.org/agrobacterium/>.

 

“Bye Bye Butterfly?  BT Corn & Its Implications.”  2000.  University of Toronto – Department of Zoology.  01 September 2002.   <http://dragon.zoo.utoronto.ca/~jlm-gmf/T0301C/technology/agrobacterium.html>.

 

Deacon, Jim.  “Biology and Control of Crown Gall (Agrobacterium tumefaciens).”  University of EdinburghInstitute of Cell and Molecular Biology. 01 September 2002.  <http://helios.bto.ed.ac.uk/bto/microbes/crown.htm>.

 

González-Cabrera, Joel, et. al.  “The Agrobacterium tumefaciens gene transfer to plant cell.”  1998.  Electronic Journal of Biotechnology.  01 September 2002.  <http://www.ejb.org/content/vol1/issue3/full/1/bip/>.

 

Hemmer, Wolfram.  “Foods Derived from Genetically Modified Organisms and Detection Methods.”  Zentrum BATS.  01 September 2002.  <http://www.bats.ch/publications/report2-97/297k12.htm>.

 

“Mercenary Microbes.”  International Society for Microbial Ecology at Michigan State University.  01 September 2002.  <http://www.microbes.org/microbes/agrobacterium.htm>.

 

Sforza, Peter, et. al.  “Pathogenesis of Crown Gall.”  Virginia Tech – Department of Plant Pathology, Physiology, & Weed Science.  01 September 2002.  <http://www.ppws.vt.edu/~sforza/prokaryote.html>.

 

 

 

 

This webpage was created by David Shelburne ’04 as an assignment for an undergraduate course—Bio 361: Genetically Modified Organisms—at Davidson College.

 

© Copyright 2002 Department of Biology, Davidson College, Davidson, NC 28035

Send comments, questions, and suggestions to: dashelburne@davidson.edu