Invasion: Type III Secretion System
Gram-negative bacteria of the genus Xanthomonas infect more than 300 different species worldwide. Xanthomonas campestris pv. vesicatoria causes bacterial spot disease on pepper and tomato plants.
- The bacteria enter the plant intercellular spaces via natural openings.
- Bacterial surface structures allow the attachment to host cells.
- Xanthomonas produces the extracellular polysaccharide xanthan that protects the bacteria from environmental factors.
- An essential pathogenicity factor is the type III protein secretion system which spans the bacterial membranes…
- … And is associated with an extracellular pilus.
- The pilus is connected to a channel-like translocon that is inserted into the plant plasma membrane.
- The type III secretion system transports approximately 30 different bacterial effector proteins into the plant cell.
- Bacterial effector proteins are transported to different cellular compartments and manipulate host cellular pathways. Some effector proteins reach the plant cell nucleus and modify plant gene expression.
- Effector proteins suppress plant defense responses and promote bacterial multiplication at the infection site.
Video by Bernd Montag, Duc Phan Tran, Felix Herbst, Frank Montag.
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