Making plants and trees which can grow in minus zero temperatures

Putting for example plants in a room and then lowering the temperature in that room a little bit every certain time
And from generation to generation.

Putting cryophilic-psychrophilic bacteria(s) in the soil.
Creating a symbiosis between psychrophilic bacteria and a plant species (which has gone through the above or is going
through the above).

Putting biological antifreeze into the ground to see if it prevents the ground from freezing.
-So the roots can for example keep on growing

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Antifreeze proteins.
psychrophilic enzymes.
Psychrophilic cellulases and proteases.

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It would be very interesting to make plants and trees which provide food to grow in subzero temperatures.