Plant Genetic Engineering—What Is Agrobacterium tumefaciens? In biotechnology, Agrobacterium tumefaciens is best described as:

Introduction / Context:
Agrobacterium tumefaciens naturally transfers a segment of DNA (T-DNA) from its Ti plasmid into plant genomes, causing crown gall disease. This biological mechanism has been repurposed to deliver transgenes into many plant species.

Given Data / Assumptions:

• Ti (tumor-inducing) plasmid harbors T-DNA and virulence (vir) genes.
• Engineered disarmed vectors remove tumor genes and carry transgenes of interest.
• Plant tissue culture enables regeneration of whole plants from transformed cells.

Concept / Approach:
The bacterium attaches to wounded plant tissue, activates vir genes, and transfers T-DNA into the plant nucleus, where it integrates into the genome. Molecular biologists exploit this system by replacing oncogenes with selectable markers and target genes, enabling stable plant transformation.

Step-by-Step Solution:

Verification / Alternative check:
Transgene presence is confirmed by PCR, Southern blotting, or reporter gene expression (e.g., GUS, GFP).

Why Other Options Are Wrong:

• It is not a human disease, nor a fungus, nor a mammalian viral vector.

Common Pitfalls:
Confusing Agrobacterium-mediated transformation (dicots easily, many monocots now feasible) with biolistics; both are used but have different efficiencies and host ranges.

Final Answer:
A bacterium that can be used to introduce DNA into plants