Scientists from the University of Exeter and Shimane University in
Japan have proved for the first time that vitamin C is essential for plant
growth. This discovery could have implications for agriculture and for the
production of vitamin C dietary supplements.
The study, which is now published online in The Plant Journal,
describes the newly-identified enzyme, GDP-L-galactose phosphorylase, which
produces vitamin C, or ascorbate, in plants. Vitamin C is already known to
be an antioxidant, which helps plants deal with stresses from drought to
ozone and UV radiation, but until now it was not known that plants could not
grow without it.

Professor Nicholas Smirnoff of the University of Exeter, lead author
on the paper said: 'Vitamin C is the most abundant antioxidant in plants and
yet its functions are poorly understood. By discovering that the new enzyme
is encoded by two genes, we were able to engineer vitamin C-free plants and
found that they were unable to grow.'

The discovery also identifies the new enzyme as a key player in
controlling vitamin C accumulation in response to light. Vitamin C provides
protection against the harmful side-effects of light during photosynthesis,
the process by which light energy is used to convert carbon dioxide into
plant matter.

Professor Nicholas Smirnoff continued: 'The discovery is exciting for
me because it is the culmination of a long-term research programme on
vitamin C in plants at the University of Exeter. It opens new opportunities
to understand fundamental growth processes in plants and to improve plant
resistance to stresses in a changing climate. In the longer term I hope that
it will contribute to the efforts of plant scientists to improve crop yield
in a sustainable manner.'

The findings could also pave the way for a new approach to producing
vitamin C dietary supplements. In Britain we spend an estimated ?20 million
on vitamin C tablets each year, making this the most widely-used dietary
supplement. Vitamin C is currently produced by mixed fermentation and
chemical synthesis. The new enzyme provides the potential to engineer
microbes to produce vitamin C by a simpler one-step process.

This research was funded by Bio-Technical Resources, Exeter University
School of Biosciences, the Japan Society for the Promotion of Science and a
Biotechnology and Biological Sciences Research Council (BBSRC) studentship.

Note: This story has been adapted from a news release issued by
University of Exeter.


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