Agrobacterium tumefaciensppt............it is a slide presentation on interkingdom gene transfer
TUMEFACIENS:UNUSUAL DISEASE AGENT
BROUGHT INTO USE AS PLANT
ABOUT THE BACTERIUM:Discovered by Smith and Townsend at 1907.
A soil—borne gram negative bacterium .it is a rod shaped and
motile and belongs to the bacterial family of Rhizobiacae .
It is a phytopathogen ,and it is regarded as Nature’s most
effective plant genetic engineer.it is the natural expert of
inter-kingdom gene transfer .
There are three kinds of Agrobacterium species :- they are .
(i) Agrobaterium tumefaciens– it induces crown gall
disease . (ii) Agrobacterium rhizogenes– it induces hairy
root disease .(iii) Agrobaterium radiobacter– it is an
A tumefacien genetically transforms plant cells and creates a
biosynthetic machinery to produce nutrients for its own
Several Dicotyledonous plants are infected by this bacterium
causing crown gall disease. But monocotyledonous plants
are difficult to transform by Agrobacterium tumefaciens .
CROWN– GALL DISEASE BY
Agrobacterium tumefaciens infects wounded or damaged part
of plants causing plant tumor called crown– gall .
The entry of the bacterium is facilitated by the release of
phenolic compounds like Acetosyringone and
Crowngall occurs when the bacterium releases its Ti
plasmid(tumor inducing) into the plant cell cytoplasm . The
T-DNA is transferred to the host cell via wounded section.
The T-DNA carries genes that code for proteins involved in the
biosysnthesis of growth hormones (auxin and cytokinin) and
novel plant metabolites namely-(opines and agropines).
The growth hormones causes plant cells to proliferate and form
gall while opines and agropines are used as sources of
carbon and energy.
MODE OF ACTION:The Ti plasmid is 200 kb having
T-DNA , the T-DNA consists
of genes for auxin(aux),
these are referred to as
The T-DNA has two borders the
Left border and the Right
border both 24 kb each .
The T-DNA has a region called
virulence region that is most
important for the transfer of
the T-DNA, example - Vir
G,vir D1/D2, vir B, vir E2 , vir
A. vir C
And genes for opine
catabolism. And a ori region
TRANSFORMATION OF CELLS BY
SIGNAL INDUCTION TO AGROBACTERIUM– by the phenolic compounds
and some sugars, induces biochemical changes that help in T-DNA
ATTACHMENT OF AGROBACTERIUM TO PLANT CELLS– agrobacterium
attaches to cell through polysaccharides and cellulose fibres.
PRODUCTION OF VIRULENCE PROTEIN– signal induction causes
virulence protein to form vir A ,which induces vir G, this then induces
the production of rest of the virulence proteins like vir D1/D2, virE, vir
PRODUCTION OF SINGLE STRANDED T-DNA-- this is recognised by vir
D and thus carried forward to the host by vir D2.
TRANSFER OF T-DNA OUT OF AGROBACTERIUM– the dna strand is
carried out by vir D2 . Through a channel made by vir B.
TRANSFER OF T-DNA INTO PLANT CELLS AND INTEGRATION—
integration of the DNA into the host cell is helped by vir E2,which
protects the dna from degradation by host cell restriction modification
system,while vir D2 helps to navigate the dna to the nucleus.
This process is called ILLEGITIMATE RECOMBINATION, since it does not
depend on the sequence similaity.
APPLICATION OF AGROBACTERIUM
MEDIATED GENE TRANSFER:--CASE 1
Recent research to produce cellulase has used to express a bacterial
cellulase gene in Lemna minor (duckweed) using A. agrobacterium. As
the interest in producing cellulosic ethanol has increase, a method for
breaking down cellulose into sugars is being seeked by scientists. A
gene for cellulase was isolated from a thermophilic bacteria and
transformed into duckweed using A. tumefaciens as the vector.
Duckweed expressing this bacterial cellulase is in no danger of
destroying its cell wall since the bacterial cellulase in question is only
active at 60 - 80 degrees Celsius. Because Duckweed is a plant with
high protein content (up to 40% of its dry weight) it is expected that it
could be turned into an efficient bioreactor for proteins such as
cellulase. However, extraction of cellulase from genetically engineered
duckweed has been complicated by the fact that a subunit of the
cellulase complexes with the cellulose of the duckweed in a form that
is hard to remove (Sun, Y.). Further engineering of the cellulase to rid
the subunit which binds to cellulose will hopefully result in a higher
yield of cellulase.
SUGARCANE:Sugarcane represents 65 % of
the world sugar production . Some natural
pharmaceutical compounds are derived
from sugarcane; additionally, agricultural
and industrial by-products of the sugar
production process are extensively
employed for animal nutrition, food
processing, paper manufacturing and fuel.
Traditional plant breeding techniques, together
with classic biotechnological approaches,
have been extensively used to increase
crop yields by selecting improved varieties
which are more productive and resistant to
diseases and pathogens. Unfortunately,
some important traits such as resistance to
insect pests and to some herbicides,
appear to be absent from the genetic pools
of sugarcane cultivars .The use of
agrobacterium mediated transformations to
introduce resistance genes into plant
genomes may have an important impact on
sugarcane yields. Recently, our group
published a report evidencing the
generation of the first transgenic
sugarcane lines resistant to stem-borer
AGROBACTERIUM USED IN GM CROPS
PRODUCTION:IN RECENT DAYS WHEN THE NEED OF GOOD AND HEALTHY STAPLE FOOD IS
INCREASING SUCH AS RICE, SCIENTIST HAVE TRIED TO INCORPORATE
SOME NUTRIENT IN TO THE RICE.
GOLDEN RICE PRODUCTION WAS DONE BY EUROPEAN SCIENTISTS BY THE
HELP OF BIOLISTIC METHOD . BUT IN RECENT TIMES THIS METHOD HAS
LOST ITSSIGNIFICANCE DUE TO HIGH RISK OF DNA AND CELL DAMAGE
IN 2004 A GROUP OF SCIENTIST FROM GERMANY (University of Freiburg,
Center for Applied Biosciences, Scha¨nzlestr. 1, 79104 Freiburg, Germany)
HAVE USED AGROBACTERIUM AS A MEDIUM AND VECTOR TO INSERT THE
GENE FOR β-CAROTENE (OR PROVITAMIN A) IN TO RICE PLANTS KNOWN
AS GOLDEN RICE 2.
THUS THE USAGE OF AGROBACTERIUM AS A INTERKINGDOM GENE
TRANSFER VECTOR IS USED IN VARIOUS ASPECTS OF HUMAN LIFE
,HAVING BOTH ECOLOGICAL , ECONOMICAL AND SCIENTIFIC VALUE.