Question

Which one of the following microorganisms is used as a cloning vector to deliver the genes of interest into a variety of plants?

• A. Bacillus thuringiensis
• B. Rhino viruses
• C. Agrobacterium tumefaciens
• D. Nucleopolyhedrovirus

Hint:

Vectors for gene transfer:
$\bullet$ Plants $\rightarrow$ Disarmed Ti-plasmid of Agrobacterium tumefaciens.
$\bullet$ Animals $\rightarrow$ Disarmed Retroviruses.

Answer 1

The Correct Option is C

Concept:
Plant genetic engineering utilizes natural vectors capable of stably transferring exogenous DNA into plant host genomes.

Step 1: Role of Agrobacterium tumefaciens as a Cloning Vector:
Agrobacterium tumefaciens is a soil-borne plant pathogen known as 'nature's genetic engineer'.
It naturally infects dicotyledonous plants and transfers a specific segment of DNA, termed T-DNA (transfer DNA), located on its tumor-inducing (Ti) plasmid into the plant nuclear genome.
In recombinant DNA technology, the pathogenic tumor-inducing genes in the Ti-plasmid are disarmed and replaced with desired genes of interest.
The modified Ti-plasmid delivers the foreign gene into the plant host genome without causing crown gall disease.

Step 2: Evaluating Alternative Options:
- Bacillus thuringiensis: A bacterium producing Cry insecticidal crystal proteins; it is not used as a cloning vector.
- Rhino viruses: Viruses causing common cold in humans.
- Nucleopolyhedrovirus: Baculoviruses used as narrow-spectrum biological control agents against insect pests.

Step 3: Final Answer:
Thus, the microorganism widely utilized as a disarmed plant cloning vector is Agrobacterium tumefaciens (Option C).