Marie Freebody, firstname.lastname@example.org
HARPENDEN, UK – Cereals, breads and pasta could be produced from wheat grain containing
higher amounts of essential minerals with a little help from x-ray vision. High-intensity
x-rays from the world-famous Diamond Light Source synchrotron in Oxford usually
are used to observe metal distribution and chemistry in various samples. Now, however,
the powerful x-rays are being redirected to carry out fluorescence analysis of wheat
Shown is a red-green-blue overlay of manganese, zinc and iron distribution in a cross
section of wheat grain. Mineral distribution is limited to the bran and germ (observed
as the large structure at the bottom of the grain). No minerals are identified in
the white flour.
Scientists at Rothamsted Research, an institute of the Biotechnology
and Biological Sciences Research Council (BBSRC), hope that their studies of wheat
could be used to grow potentially life-saving mineral-enriched flour.
“Iron and zinc deficiency has been estimated by the World
Health Organization to affect billions of people worldwide, with deaths totaling
over 1 million people every year,” said Dr. Andrew Neal, who leads the BBSRC-funded
project. “These deficiencies arise not because of a lack of minerals in soils,
but because wheat and other cereals lay down only limited amounts of minerals in
grain tissue. By increasing the amount of minerals that plants allocate to the grain,
a more nutritious staple diet could be provided, and many of these deaths could
This heat map representation is based upon fluorescence intensity
(blue, low; red, high) of minerals in a cross section of wheat grain. Again, the
distribution of minerals – manganese (Mn), zinc (Zn), iron (Fe), nickel (Ni)
and copper (Cu) – is limited to the bran and germ (observed as the large structure
at the bottom of the grain). Images courtesy of Dr. Andrew Neal.
Most of the mineral content of grain is contained in the bran
and germ, but when grain is milled to produce white flour, much of the mineral content
is lost and therefore missing from our diet. By studying the mineral contents and
distribution in grain, the new technique will identify grain varieties that contain
increased levels of minerals in the white flour. These new varieties can then be
used to develop new commercially available wheat.
At the same time, newly developed varieties that do not contain
increased flour-associated minerals can be identified rapidly so that further experimental
effort is not wasted on them.
So far, the Rothamsted team has developed techniques of sectioning
and visualization that use highly focused x-ray beams to image the distribution
of minerals via x-ray fluorescence. This means that distribution data can be collected
on a number of minerals simultaneously.
Until now, the only approach was to stain a limited number of
minerals one at a time and to observe grains microscopically. “Not only can
we now observe many elements in a single grain, we are also able to interrogate
the complexation of each mineral,” Neal said. “Mineral complexation
is important because it determines the bioavailability – digestibility –
in the grain.”
The synchrotron-based approach provides a relatively rapid method
of visualizing the mineral distribution within current and new grain varieties.
In the imaging process, the synchrotron accelerates and directs electrons at speeds
very close to the speed of light to provide high-intensity x-ray beams.
Wheat grains are sectioned and mounted in epoxy resin at a 45°
angle to the incident x-rays on an X-Y-Z stage. The sample then is moved in a stepwise
manner so that its fluorescence is collected at discrete points, enabling eventual
study of the whole sample.
“The fluorescence intensity due to each element in the sample
is analyzed by software, and the resulting two-dimensional maps are produced,”
Neal said. “We have studied two new grain varieties that contain three times
as much iron as current wheat varieties. However, fluorescence mapping has detected
that the additional iron is stored in the bran of both varieties but is not transported
across the bran into the white flour.”
In the next stage of analysis, Neal and colleagues hope to determine
not only which cells are preventing the further transport of iron but also the iron
chemistry in the cells. This information will be of great use to plant breeders
who can employ the Rothamsted results to develop new varieties in which iron transport
into the white flour is not limited.