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How Plants Control Vitamin C Production Revealed

Research published in Plant Cell has revealed how plants regulate vitamin C levels in each of their cells in response to the environment.

“Understanding these mechanisms may help in plant breeding programs to produce hardier plant crops and improve human health, because iron deficiency anaemia is the most common form of mal­nutrition worldwide,” said Prof Roger Hellens of Queensland University of Technology. “This discovery will also help us to understand why some plants such as the Kakadu plum are able to accumulate super-high levels of vitamin C.”

Hellens said that plants responded to factors in the environment like extreme light or drought by producing vitamin C, a powerful antioxidant, to protect themselves from damage. “Each cell assesses whether it should produce more of the antioxidant, which would absorb the energy from the high levels of light or stop the damaging oxidative process in a dehydrated plant,” Hellens said.

“In vitamin C regulation it is the ascorbate molecules which interact with a critical enzyme in the biochemical pathways to make vitamin C. Plants can move the level of ascorbic acid between cells as needed.”

Hellens said plants had two ways to regulate cell processes. “One way is during transcription, when DNA is turned into the messenger molecule RNA, the molecule that distinguishes cells into different types of tissue. The second way is to regulate while turning RNA into an enzyme that makes vitamin C.

“So if a cell wants to increase its level of vitamin C it’s generally got two ways to do it – and we’ve discovered vitamin C uses the second method, and in an unexpected way. We discovered it’s not whether the cell is making the RNA but whether the RNA is converted into a protein that is the deciding mechanism.

“It’s very interesting because we found it was the level of vitamin C itself in each cell that decides whether RNA turns into the protein which makes vitamin C.”