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Formation of extracellular structures containing VirB2 proteins in mating cultures of agrobacteria
1Institute of Biochemistry and Physiology of Plants and Microorganisms, Russian Academy of Sciences, Saratov.
Abstract:
Using transmission electron immunomicroscopy, VirB2 protein has been revealed at the surface of acetosyringon-treated A. tumefaciens cells. VirB2 was seen within long flexible and short structures localized at the opposite poles of the cells. These structures were not observed in cells not treated with acetosyringon and in agrobacterial cells treated with this reagent but carrying no Ti-plasmid. Labeled complexes [antibodies to virB2 protein + (A protein + colloidal gold)] bound to pili at a certain periodicity.
Insights
Agrobacterium tumefaciens VirB2 protein forms pili structures on cell surfaces after acetosyringone treatment. These pili are essential for bacterial conjugation and were visualized using transmission electron immunomicroscopy.
Area of Science:
- Microbiology
- Molecular Biology
- Cell Biology
Background:
- Agrobacterium tumefaciens is a plant pathogen that transfers DNA to plant cells.
- The VirB/D4 type IV secretion system (T4SS) is crucial for this DNA transfer.
- VirB2 is a major component of the T4SS pilus structure.
Purpose of the Study:
- To visualize the localization and structure of VirB2 protein on A. tumefaciens cells.
- To investigate the role of acetosyringone in inducing pilus formation.
- To confirm the association of VirB2 with pili structures.
Main Methods:
- Transmission electron immunomicroscopy was used to examine A. tumefaciens cells.
- Acetosyringone treatment was applied to induce pilus formation.
- Antibodies against VirB2 protein and colloidal gold labeling were employed for visualization.
Main Results:
- VirB2 protein was detected on the surface of acetosyringone-treated A. tumefaciens cells.
- These VirB2 proteins formed long, flexible, and short structures at the cell poles.
- Such structures were absent in untreated cells or cells lacking the Ti-plasmid.
- Labeled antibody complexes bound to pili with a specific periodicity.
Conclusions:
- Acetosyringone treatment induces the formation of pili composed of VirB2 protein in A. tumefaciens.
- These pili are localized at the cell poles and are dependent on the Ti-plasmid.
- The findings provide direct evidence for VirB2's role in pilus assembly and function.