Which one of the following types of promoters would NOT be used within the T-DNA for expression of a negative selection marker gene for generation of transgenic plants by Agrobacterium-mediated transformation?

Correct option is A

In Agrobacterium-mediated transformation, a negative selection marker gene is used to eliminate unwanted cells(either non-transformed or incorrectly transformed cells). The type of promoter used to drive this marker gene plays a crucial role in determining its effectiveness.

A strong constitutive promoter is not suitable for a negative selection marker because:

1. It is always active in all plant cells, making it impossible to selectively remove transformed cells at specific stages.
2. It may harm the entire plant, especially if the selection marker is toxic (e.g., Barnase or CodA).
3. Uncontrolled expression can affect plant growth and regeneration, reducing transformation efficiency.

Additional Information

• Option (2) Tissue-Specific Promoter (Incorrect)

  • Tissue-specific promoters may work, but they do not provide complete control over negative selection, restricts expression to certain tissues, allowing selective elimination

• Option (3) Substrate-Inducible Promoter (Incorrect)

  • These promoters allow conditional expression, making them effective for negative selection, can be turned on/off using a specific chemical (e.g., tetracycline-inducible promoters) .

• Option (4) Stress-Inducible Promoter (Incorrect)

  • Expression under specific stress conditions allows selective removal, making it suitable.