US scientists find key to cold tolerance in corn

Plants are divided into two groups - C4 and C3 - based on their ability to garner light energy. The C4 groups include corn, sorghum and sugarcane, while wheat and rice belongs to C3 groups. C4 plants have four extra chemical steps than C3 plants, which made the former more efficient in converting sunlight energy into plant matter.

Until recently, C4's higher productivity was thought to be possibly only in warm environments, but a wild C4 grass related to corn - Miscanthus x giganteus – has been found to be exceptionally productive in cold climates.

No differences in DNA and behaviour were found when scientists examined the enzyme called Pyruvate Phosphate Dikinase (PPDK) in both plants. However, when corn leaves were placed in the cold, PPDK slowly disappeared in parallel with the decline in the leaf's ability to absorb carbon dioxide in photosynthesis. Miscanthus leaves were totally different as they produced more PPDK and was able to maintain photosynthesis in cold conditions.

The scientists cloned the PPDK gene from both plants into a bacterium, enabling the isolation of large quantities of this enzyme. It was discovered that the difference between the two plants was the amount of protein present rather than the structure of protein components, as the enzyme was found to be cold-resistant in a concentrated form.

This finding suggests that modifying corn to synthesise more PPDK during cold weather could allow corn to be cultivated in colder climates and be production for more months of the year in its current locations.

Global corn demand is higher than supply, which led to sharp price increases that are expected to continue over the next several years.