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Tomatoes, genetically engineered to contain high levels of folate, could
provide the recommended daily amount in one standard serving, says new
research, March 2007 by Stephen Daniells.

Researchers from the University of Florida have created transgenic
tomatoes that express 25 times more folate than normal tomatoes, and may
offer up to seven times more folate than green leafy vegetables, considered
a rich source of the vitamin.

Folate is found in foods such as green leafy vegetables, chick peas and
lentils, and an overwhelming body of evidence links has linked folate
deficiency in early pregnancy to increased risk of neural tube defects
(NTD) - most commonly spina bifida and anencephaly - in infants.

This connection led to the 1998 introduction of public health measures in
the US and Canada, where all grain products are fortified with folic acid -
the synthetic, bioavailable form of folate.

"However, food fortification can be difficult to implement in developing
countries due to recurrent costs, distribution inequities, and a lack of an
industrial food system," wrote lead author Rocio Díaz de la Garza. "Folate
enhancement in plant foods (biofortification) through metabolic engineering
therefore represents an attractive alternative strategy to increase the
intake of natural folates in rich and poor countries alike."

Writing in the Proceedings of the National Academy of Sciences, the
researchers report that by genetically engineering two different tomato
strains to each overproduce one folate precursor (pteridine or
p-aminobenzoate (PABA)), and then crossing these two strains, the resulting
ripe fruit contained 25-fold more folate than normal tomatoes.

The tomatoes were transformed using the Arabidopsis aminodeoxychorismate
synthase (AtADCS) and CTP cyclohydrolase I (GCHI) to lead to PABA, pteridine
and folate hyperaccumulation.

Tomatoes that expressed both genes were found to accumulate about 840
micrograms of folate per 100 grams of fruit, enough to provide the RDA for a
pregnant women "in less than one standard serving," said the researchers.

"To our knowledge, the folate levels we achieved are the highest reported
for plants; our tomatoes accumulate up to seven times more folates than
green leafy vegetables, which are considered rich folate sources," they
said.

The researchers also note that the concentrations of the folate precursors
are likely at safe consumption levels, but stated that more research is
required to fully assess the potential and safety of accumulated pteridines
in GM fruit and plants.

"It should be noted that the success of our-two-gene biofortification
strategy is likely to be repeatable in other plants? and may well be
transferable to other food plants such as tubers and cereal grains,"
concluded the researchers.

A number of genetically modified plants and crops are coming to light with
enhanced nutritional content considered to offer human health benefits,
including flavonoid-rich tomatoes, zeaxanthin in potato tubers, and the
omega-3 fatty acid, eicosapentaeoic acid (EPA), to soybeans, brassica, and
stearidonic acid (SDA) in canola crops.

However, no GM crops with potentially enhanced health benefits have been
approved for human consumption. Consumer acceptance, particularly in Europe
and most notably in the UK, continues to be one of the biggest challenges
for these crops.

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