A Purdue University scientist has found genetic evidence of how
some plants adapt to live in unfavorable conditions, a finding he
believes could one day be used to help food crops survive in new or
changing environments.
David Salt, a professor of horticulture, noticed several years ago
that a variant of the research plant Arabidopsis thaliana that
could tolerate higher levels of sodium had come from coastal areas.
To test the observation, Salt grew more than 300 Arabidopsis
thaliana plants from seeds gathered across Europe. The plants were
grown in non-saline soil and their leaf-sodium content was
measured.
Each plant's origination was mapped, and those with the highest
sodium contents were found to have come from seeds collected close
to a coast or area with high saline soil. All plants were analyzed
using genome-wide association mapping, which compares the genomes
of a number of plants with a shared physical trait - in this case
leaf sodium accumulation - to identify genes that may account for
variation in this characteristic. Salt found that the plants that
accumulate the highest sodium levels in their leaves had a weak
form of the gene HTK1, which regulates sodium intake distribution
to leaves.
"The major gene that is controlling variation in leaf sodium
accumulation across the whole European population of Arabidopsis
thaliana is HTK1," said Salt, whose findings were published in the
journal PLoS Genetics. "The Arabidopsis thaliana plants that
accumulated high levels of sodium had a reduced level of HTK1 gene
expression. The populations that have this altered form of HTK1 are
on the coast. There are a few exceptions that prove the rule, such
as populations in the Czech Republic, which isn't near the coast,
but come from an area containing high saline soils derived from an
ancient beach."
It has long been known that plants are adapted to their local soil
environments, but the molecular basis of such adaptation has
remained elusive. Salt said this is some of the first evidence
linking genetic changes with adaptation to specific environmental
factors.
"What we're looking at is evolution in action," Salt said. "It
looks like natural selection is matching expression of this gene to
the local soil conditions."
Salt said crops grown around the world could be affected, possibly
negatively, by climate change. It may become important to identify
mechanisms to adapt plants to drought conditions, higher
temperatures or changes in soil nutrition. Salt believes
identifying genetic mechanisms of how plants naturally adapt to
their environments will be key to solving those problems.
"Driven by natural selection, plants have been evolving to grow
under harsh conditions for millennia," Salt said. "We need to
understand genetically what is allowing these plants to survive
these conditions."
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Thanks to Purdue University for this article.