Agrobacterium Gene Transfer Method

Questions and Answers

What is the primary role of Agrobacterium tumefaciens in plant transformation?

It provides nutrients to the plant cells.

It acts as a fertilizer for plant growth.

It serves as a natural vector for gene transfer. (correct)

It protects plants from pests and diseases.

Which step involves the integration of T-DNA into the plant genome?

Sensing plant signals by agrobacterium.

Nuclear import of T-DNA and effector proteins.

Attachment of agrobacterium to the plant.

T-DNA integration and expression. (correct)

What is acetosyringone's role in the Agrobacterium tumefaciens gene transfer method?

It aids in the synthesis of plant hormones.

It promotes the release of T-DNA into soil.

It activates virulence in the bacteria. (correct)

It serves as an energy source for the plant.

Which region of the Ti plasmid is responsible for the synthesis of auxin and cytokinin?

<p>T-DNA region.</p> Signup and view all the answers

Which virulence gene is primarily involved in the cleavage of a supercoiled stranded substrate?

<p>VirD1.</p> Signup and view all the answers

Study Notes

Agrobacterium Gene Transfer Method

Agrobacterium tumefaciens is a gram-negative bacterium, pivotal in plant transformation, and is the agent causing crown gall disease.
This bacterium targets wounded plants by detecting amino acids, sugars, and organic acids released from them.
It attaches to damaged plant tissue using a polar attachment mechanism.

Transformation Steps

Initial attachment of Agrobacterium to plant tissue.
Sensing plant signals induces the regulation of virulence genes.
T-DNA and virulence proteins move from the bacterium into the plant cells.
T-DNA and effector proteins are imported into the plant nucleus.
Integration and expression of T-DNA occur within the plant genome.

Ti Plasmid

The Ti plasmid is a circular DNA segment crucial for transformation.
It has three key regions:
- T-DNA region, which integrates into the plant genome.
- Oncogene, responsible for tumor formation.
- Virulence region containing 24 genes essential for bacterial infection and transformation.

Virulence Genes

VirA: Senses acetosyringone, a plant signal.
VirG: Acts as a transcriptional activator for virulence genes.
VirB: Creates conjugation pores between bacterial and plant cells.
VirD1: Cleaves substrate, facilitating T-DNA processing.
VirE: Produces the gene transfer protein essential for T-DNA transport.
VirC: Aids in the DNA transfer process.
VirB11: Has ATPase activity that powers the DNA transfer mechanism.

Mode of Action

Infected plant cells begin to divide, forming tumors.
Tumors produce opine, an energy source exploited by Agrobacterium.
The bacterium's entry into plants is enhanced by phenolic compounds like acetosyringone.
Acetosyringone activates virulence factors in Agrobacterium.
Virulence proteins synthesize single-stranded T-DNA, which is then transferred into plant cells.
The T-DNA complex is imported into the nucleus and integrates randomly into plant chromosomes.
This integration triggers synthesis of auxin and cytokinin, leading to tumor formation in infected plant cells.

Description

This quiz explores the Agrobacterium tumefaciens gene transfer method, detailing its role in plant transformation and the process of how it integrates T-DNA into the plant genome. Understand the significance of the Ti plasmid and the molecular mechanisms involved in this transformation.