Nature's remedy for stressed-out plants.

Studies of the wispy little field plant Arabidopsis reveal that many organisms may have found a common way to cope with stress, beginning eons ago with their earliest ancestors.

Stresses such as heat, drying, and even exposure to alcohol can damage cells by interfering with essential proteins that catalyze reactions or give cells structure. The proteins may get distorted, or they may aggregate in useless clumps.

For almost a decade, scientists have known how animal and bacterial cells cope. They generate hardy molecules called heat shock proteins that not only resist stress but also can rescue their susceptible protein brethren. At the first sign of high temperature, for example, the genes for heat shock proteins turn on, churning out the protective molecules until the stress subsides.

Heat shock proteins appear to work by binding to distorted proteins, straining chemical bonds until they break. The bonds then form correctly.

Until recently, no one knew whether plants had heat shock proteins. But a University of Chicago research team studying a heat shock protein in yeast also found such a protein in Arabidopsis. "We've found heat shock proteins in every plant type we've tested," says lead researcher Susan Lindquist.

"Organisms often have to cope quickly with changes in their environment," she says. "It looks like this solution arose early in evolution." Today, both primitive and recently evolved organisms use heat shock proteins.

The team found that Arabidopsis produces the helpful proteins in large amounts in seeds during their maturation, with peak production in the older, dry seeds. The proteins disappear, the researchers say, when the plant germinates.

In work presented this month at the annual meeting of the American Society for Cell Biology in Washington, D.C., Lindquist speculated that "dryness could cause seed proteins to aggregate." Heat shock proteins could insulate seeds against such effects, she says.

Because the team has found that heat shock proteins generated in too-warm leaves differ from those in drying seeds or in watered roots, Lindquist concludes that "different types of protein may appear for different types of stress."