Q74.Agrobacterium tumefaciens is used for transformation in plant tissue culture because
(1) Both Agrobacterium and plants have similar genetic make-up
(2) Agrobacterium genomic DNA can transfer its genetic material to plants
(3) vir genes of Agrobacterium aid in T-DNA transfer to plants
(4) All of these
Agrobacterium tumefaciens revolutionizes plant genetic engineering by naturally transferring DNA into plant cells, making it a cornerstone of plant tissue culture transformation. The correct answer is option (3), as the vir genes are specifically responsible for enabling T-DNA transfer.
Correct Answer
(3) vir genes of Agrobacterium aid in T-DNA transfer to plants. The vir (virulence) genes on the Ti plasmid are induced by plant wound signals like acetosyringone, encoding proteins for T-DNA processing, export via type IV secretion, and nuclear integration in plants.
Option Breakdown
Both Similar Genetic Make-up (Incorrect)
Agrobacterium (bacteria) and plants (eukaryotes) have fundamentally different genomes—no shared makeup enables transformation. The process relies on Ti plasmid machinery, not genomic homology.
Genomic DNA Transfer (Incorrect)
Agrobacterium transfers T-DNA from its Ti plasmid, not genomic (chromosomal) DNA. Plasmid-specific elements ensure single-stranded T-DNA excision and delivery.
Vir Genes Aid T-DNA Transfer (Correct)
Vir genes (virA–virG, etc.) form a regulon activated by plant phenolics, producing proteins like VirD2 (protects T-DNA ends) and VirE2 (coats T-strand for transport).
All of These (Incorrect)
Options (1) and (2) are false; only (3) holds true. Transformation depends solely on Ti plasmid’s T-DNA and vir regions.
Transformation Process
Agrobacterium infects wounded plant tissue, vir genes activate, T-DNA integrates randomly into the plant genome, enabling stable transgenics for crops like cotton and rice.
