The evolution of the mustards' spice

August 30, 2012

The tangy taste a mustard plant develops to discourage insect predators can be the difference between life and death for the plants. A new study has used this trait and its regional variations to conquer the difficult task of measuring the evolution of complex traits in a natural environment.

There's a reason people don't put gobs of mustard on a hot dog. Mustard plants produce a spicy chemical intended to discourage insects from eating them lest they suffer a bad case of heartburn, and it has essentially the same effect on us.

Now, an interdisciplinary and international group of researchers based at Duke University has figured out why some of those wild mustard plants vary as much as they do in terms of that spice. The variation spells the difference between life and death for the plants in the mountainous Rockies where they live, a place where can change quite significantly over relatively short distances.

The study reported in the August 31 issue of the journal Science is one of very few to successfully follow the genes underlying variation of complex traits in a natural setting back to the that influenced them.

"We were able to put this story together all the way from the plants in the dirt to the in the laboratory," said Tom Mitchell-Olds, a professor of biology and member of the Duke Institute for & Policy. "That's where the challenge came in."

Mitchell-Olds' team studies the wild mustard Boechera stricta. Boechera is their organism of choice because its close relationship to the laboratory plant Arabidopsis offers them technical advantages and because the plants live in areas that have been untouched and unchanged for the last 3,000 years.

The researchers first identified a broad region in the plants' genome that was responsible for differences in their chemical defenses, vulnerability to insects and survival and reproduction in nature. "Technically, we had no idea what this would be," Mitchell-Olds said.

Ultimately, they traced those differences back to two amino acid changes in the enzyme controlling the plants' main spicy ingredient. With sophisticated biochemistry, the researchers discovered that this seemingly slight difference alters the spice-building pathway to produce a different defensive chemical—different in a way that apparently matters quite a lot to insects. When plants carrying the version of that enzyme normally found in Colorado were planted in Montana, they struggled to survive as insects took their toll. When Montana were established in Colorado, they too got hammered by bugs.

While the findings may have some agricultural applications, Mitchell-Olds says he is more interested in understanding natural variation and the evolutionary forces that have shaped that variation over thousands of years.

"We've been able to go to places where the environment is intact, where these genotypes have been sitting around for 3,000 years in the place where they evolved in the first place, and do science," Mitchell-Olds said. "This variation we see reflects history. We finally have the tools to find the genes and to understand their influence on physiology and fitness, and that's pretty cool."

Explore further: Insects use plant like a telephone

More information: "A Gain of Function Polymorphism Controlling Complex Traits and Fitness in Nature," K Prasad, B-H Song et al. Science, Aug. 31, 2012. DOI: 10.1126/science.1221636

Related Stories

Insects use plant like a telephone

April 23, 2008

Dutch ecologist Roxina Soler and her colleagues have discovered that subterranean and aboveground herbivorous insects can communicate with each other by using plants as telephones. Subterranean insects issue chemical warning ...

Over time, an invasive plant loses its toxic edge

September 1, 2009

Like most invasive plants introduced to the U.S. from Europe and other places, garlic mustard first found it easy to dominate the natives. A new study indicates that eventually, however, its primary weapon - a fungus-killing ...

Global warming may reroute evolution

February 16, 2011

( -- Rising carbon dioxide levels associated with global warming may affect interactions between plants and the insects that eat them, altering the course of plant evolution, research at the University of Michigan ...

Production of mustard oils: On the origin of an enzyme

March 17, 2011

( -- In the evolutionary arms race, small changes can be sufficient to gain a crucial advantage over the enemy. Scientists at the Max Planck Institute for Chemical Ecology found out recently that the ancestor ...

Plants and caterpillars make the same cyanide

April 13, 2011

( -- With an amazing example of convergent evolution, Niels Bjerg Jensen of the University of Copenhagen published a report in Nature Communications discussing the bird's-foot trefoil plant and the burnet moth ...

Recommended for you

Fecal mimicry found in seeds that fool dung beetles

October 6, 2015

(—A team of researchers with the University of Cape Town and the University of KwaZulu-Natal, both in South Africa, has found an example of a seed from a plant using mimicry to fool a beetle. In their paper published ...

A better way to read the genome

October 9, 2015

UConn researchers have sequenced the RNA of the most complicated gene known in nature, using a hand-held sequencer no bigger than a cell phone.


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.