How does Agrobacterium-mediated transformation introduce foreign DNA into plant genomes?

• A. Agrobacterium transfers T-DNA from a plasmid into plant cells, but T-DNA does not integrate into the plant genome.
• B. It directly injects DNA into plant mitochondria without integration.
• C. It uses viral vectors to deliver DNA to chloroplasts.
• D. Agrobacterium-mediated transformation transfers T-DNA from a plasmid into plant cells, and the T-DNA integrates into the plant genome.

Answer: (D)

This is about how Agrobacterium transfers DNA to plants and how that DNA becomes part of the plant genome. The bacterium uses its Ti plasmid to move a defined DNA segment, the T-DNA, into a plant cell. The T-DNA is bordered by left and right border sequences that specify what is transferred. Virulence proteins form a transfer machinery that ferries the T-DNA into the plant cell and into the nucleus. Once inside, the T-DNA is converted to double-stranded DNA and integrated into the plant genome through the plant’s DNA repair processes, producing a stable, heritable insertion of the foreign genes. Because integration is into the nuclear genome, the new genes are expressed by the plant and passed to offspring. This process does not involve injecting DNA into mitochondria or chloroplasts, and it does not use viral vectors.