A Purdue
Univ. 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 Arabidopsisthaliana 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.”
Salt plans to continue his research to understand at the
DNA level how Arabidopsis thaliana adapts
to environmental conditions. The National Institutes of Health funded his work.
