Genetically modified plants can be developed that perform
significantly better than existing varieties in dry and saline soils. This
is the conclusion of the doctorate thesis, to be defended by Shital Dixit at
Wageningen University on March 14.
Dixit discovered genes that radically enhance the seed production of
rice and Arabidopsis plants in dry and saline conditions. This is a major
breakthrough considering the rising demands for food and the effects of
climate change.

The constantly rising world population and the changing climate will
make it essential in the future to cultivate crops in soils where current
varieties are unproductive. These so-called marginal soils are often too dry
or contain too much salt for cultivation. There are many such areas around
the world that are currently not being used for food production, and climate
change will lead to huge increases in marginal soils.

Varieties that are less susceptible to drought and/or salt might make
it possible to grow crops in marginal soils. Within plant biology, there are
mechanisms known which allow plants to protect themselves against the a
biotic stress caused by a lack of water or excessive salt. Using
the genes which set these mechanisms into action and genetic
modification, varieties can be developed which make the most of these
mechanisms and are therefore resistant to drought and salt.

Shital Dixit studied the so-called 'HARDY' gene, found in a collection
of Arabidopsis mutants in which certain jumping genes increase the
activity of genes. Via genetic modification, Dixit developed
Arabidopsis
plants in which the HARDY gene was more active. She discovered that
these genetically modified plants grew better under drought stress
than
ordinary Arabidopsis plants. The 'HARDY plants' used water more
efficiently than normal plants. During desiccation of the soil, the
plants were found to vaporise considerably less water while
maintaining
their growth. When the soil was dry, the HARDY plants lived on and
recovered after being given water. They also proved to be resistant
against high saline concentrations in the soil.

By means of genetic modification, Dixit managed to transfer the HARDY
gene to rice. The HARDY rice plants also turned out to be tolerant to
both drought and salt. To Dixit's surprise, these improved rice plants
also performed at least as well in optimal cultivation conditions as
ordinary rice plants. The general rule in plant biology is that plants
with increased stress tolerance perform worse in optimal conditions
than
plants without tolerance. This makes the HARDY system even more
promising in practical applications.

The HARDY gene encodes for a so-called transcription factor, meaning
that a whole chain of genes is regulated. A plant can therefore turn
an
entire drought or salt tolerance mechanism on or off with a single
switch. Dixit also discovered that the SHINE gene, which also encodes
for a transcription factor, is capable of making rice tolerant to salt
as well.

In her research, Dixit showed how a large group of plants with
mutations
that cause genes to be more active can be valuable for tracking genes
that increase stress tolerance. Dixit selected two mutants from one of
these plant groups, which after more detailed research proved to use
water more efficiently and to have a tolerance for higher saline
concentrations.

Dixit performed her research at Plant Research International
(Wageningen
UR). It was financed by the WOTRO programme of The Netherlands
Organisation for Scientific Research (NWO).


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