Cold-tolerant transgenic plants: Which strategy has been used to improve cold tolerance by leveraging cold-responsive gene networks?

Introduction / Context:
Low temperatures activate a suite of cold-responsive (COR) genes that adjust membrane composition, osmolyte levels, and protective proteins. Transgenic strategies frequently target upstream regulators to coordinate broad protective responses rather than inserting single effector genes.

Given Data / Assumptions:

• Cold tolerance involves many downstream genes.
• Transcription factors such as CBF/DREB bind to CRT/DRE elements to induce COR genes.
• The question focuses on a general strategy, not a specific gene name.

Concept / Approach:
Overexpressing master regulators (e.g., CBF1/3) can pre-activate cold acclimation pathways under normal temperatures, resulting in improved freezing tolerance. While inducible promoters are often preferred to avoid growth penalties, constitutive expression demonstrates the concept clearly and has been reported in model plants.

Step-by-Step Solution:

Verification / Alternative check:
Peer-reviewed work shows that constitutive CBF/DREB expression elevates proline/sugars and alters membrane lipid profiles, improving survival at low temperatures (though with possible growth trade-offs).

Why Other Options Are Wrong:

• Peltier devices: not a biological transgenic strategy.
• Ethylene glycol production: toxic and not a plant antifreeze strategy.
• Evaporative cooling: counterproductive in cold stress and risks desiccation.
• Pigment replacement: not central to cold tolerance mechanisms.

Common Pitfalls:
Assuming single “antifreeze” compounds suffice; ignoring regulatory control that coordinates many protective mechanisms.

Final Answer:
Constitutive expression of a transcriptional activator that turns on cold-induced genes