Question

Somatic embryogenesis is a desired method of plant regeneration for plant transformation because

• A. It mainly results into chloroplast transformation
• B. It largely favours marker-free transgenics
• C. It produces confirmed transgenics
• D. It produces chimeric transgenics

Hint:

Somatic embryogenesis $\approx$ Single Cell origin $\rightarrow$ Non-chimeric plants.
Organogenesis $\approx$ Multicellular origin $\rightarrow$ Risk of Chimeras.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
In plant genetic engineering, regenerating a whole plant from transformed cells is a prerequisite. Two main pathways exist: organogenesis (forming shoots and roots) and somatic embryogenesis (forming embryo-like structures).

Step 2: Detailed Explanation:
One of the biggest hurdles in plant transformation is the formation of chimeras. A chimera is a plant where only some cells or tissues are transgenic (contain the new DNA), while others are wild-type. This happens frequently in organogenesis because shoots often arise from a group of multiple cells (multicellular origin).
Somatic embryogenesis is preferred because a somatic embryo usually originates from a single cell (unicellular origin). When that single cell is successfully transformed and then induced to form an embryo, every single cell in the resulting plant will carry the transgene. This results in confirmed transgenics (also called "uniform" or "solid" transgenics) and avoids the problem of chimerism.
- Option 1 is incorrect as chloroplast transformation depends on the delivery method (biolistics), not the regeneration pathway.
- Option 2 is incorrect as marker-free systems are a separate technological goal.
- Option 4 is incorrect because the avoidance of chimeras is the reason it is desired.

Step 3: Final Answer:
Somatic embryogenesis is favored because its unicellular origin ensures that regenerated plants are fully transgenic and non-chimeric. Option 3 is correct.