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Agrobacterium tumefaciens
• Agrobacterium
tumefaciens is a
Gram-negative soil
phytopathogen.
Agrobacterium tumefaciens
• Agrobacterium affect
most dicotyledonous
plants in nature,
resulting in crown gall
tumors at the soil-air
junction upon tissue
wounding.
Agrobacteria that causes
neoplastic diseases in plants
• Agrobacterium rhizogenes (hairy root
disease).
• Agrobacterium rubi (cane gall disease)
• Agrobacterium tumefaciens (crown gall
disease)
• Agrobacterium vitis (crown gall of grape)
What will Agrobacterium
tumefaciens affect in plants?
• Crown gall disease is not
generally fatal, but it will
reduce plant vigor and
crop yield, and crown
galls will attract other
phytopathogens or pests.
• In some cases, necrosis or
apoptosis is observed after
Agrobacterium infection.
Host range of Agrobacterium
• Agrobacterium has the broadest host range of any
plant pathogenic bacterium.
• Angiosperms: numerous species, including
monocots and dicots.
• Gymnosperms: mostly genus Pinus. There was a
report about transforming larch (Larix)
• Microorganisms: fungi, yeasts, ascomycetes, and
blasidiomycetes.
• Human cells: Hela cells
The discovery of Agrobacterium
• In 1897, Fridiano Cavara identified a
flagellate, bacilloid bacterium as a casual
agent of crown gall of grape.
• This organism is Agrobacterium vitis,
causing the growth of neoplastic tumors on
the stem and crown of grapevines and
inducing necrotic lesions on grape roots.
The initiation of Agrobacterium
infection
• Agrobacteria usually infects plants from their
wounds, which occurred quite frequent after frost.
• In practice, protection from subfreezing winter
temperatures and control of chewing insects and
nematodes can prevent infection by agrobacteria.
• Avirulent Agrobacterium strains like
Agrobacterium radiobacter K84 and its plasmidtransfer-deficient derivative K1026 strains were
proven to be effective in controlling infection.
Agrobacterium infect the ovaries
of flowers
• Agrobacterium infects flowers that were
developmentally young at the time (6-11 days
away from anthesis; equivalent to 5-10 days after
inoculation).
Agrobacterium infect the ovaries
of flowers
• GUS staining can only
be observed in ovaries
5 days after
inoculation and is
vanished 12 days after
inoculation.
How can Agrobacterium infects
the ovaries of flowers?
• Because the
gynoecium of
Arabidopsis were
formed by two carpels
and they remained
separated until three
days before anthesis
(flowering).
Agrobacterium tumefaciens
膿桿菌
Left Border and Right Border
transfer
(Tumor-inducing)
Binary vector system
Steps of Agrobacterium-plant cell
interaction
1. Cell-cell recognition
2. Signal transduction and transcriptional
activation of vir genes
3. Conjugal DNA metabolism
4. Intercellular transport
5. Nuclear import
6. T-DNA integration
T-pilus usually wind into
compact coils to bring the
bacterium and host cell closer
Right T-DNA border
CaMV 35S PR
MCS
nptII(KanR)
Neomycin phosphotransferase
Left T-DNA border