Agrobacterium and T-DNA delivery at wound sites Which organism naturally transfers a defined set of genes encoded on the T-DNA region of a Ti plasmid into plant cells at wound positions during crown-gall disease?

Introduction / Context:Natural genetic engineering by Agrobacterium tumefaciens underpins modern plant transformation. The bacterium detects plant wound signals, activates virulence genes, and transfers T-DNA into host cells, where it integrates and alters plant metabolism.

Given Data / Assumptions:

• T-DNA resides on the Ti (tumor-inducing) plasmid.
• Transfer occurs at plant wound sites due to phenolic inducers (e.g., acetosyringone).
• The pathogen responsible for crown-gall is Agrobacterium tumefaciens.

Concept / Approach:

Virulence genes (virA/virG, virB, virC, virD, virE) orchestrate T-DNA processing and a type IV secretion system to deliver the single-stranded T-strand into plant cells. No plant species listed performs this transfer; it is a bacterial process.

Step-by-Step Solution:

Verification / Alternative check:

Classic plant pathology and molecular studies identify A. tumefaciens as the vector of T-DNA into wounded plant tissue.

Why Other Options Are Wrong:

Wild tomatoes and grasses are hosts, not vectors. Pseudomonas syringae causes different diseases and does not transfer Ti-plasmid T-DNA.

Common Pitfalls:

Misinterpreting host names as causal transfer agents.

Final Answer:

Agrobacterium tumefaciens