Agrobacterium tumefaciens

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Agrobacterium tumefaciens

• Agrobacterium tumefaciens is a Gram-negative soil
  phytopathogen.

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Agrobacterium tumefaciens

• Agrobacterium affect most dicotyledonous plants
  in nature, resulting in crown gall tumors at the
  soil-air junction upon tissue wounding.

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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)

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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.

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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

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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.

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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
  plasmid-transfer-deficient derivative K1026
  strains were proven to be effective in
  controlling infection.

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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).

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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.

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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).

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Agrobacterium tumefaciens ???
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transfer
Left Border and Right Border
(Tumor-inducing)
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Binary vector system
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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

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T-pilus usually wind into compact coils to bring
the bacterium and host cell closer
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