The circle of life

The Economist:

The age-old puzzle of how, after a wildfire, long-dormant seeds in the soil get a wake-up call has finally been pieced together by a team at the Salk Institute and nearby University of California, San Diego. As trees and shrubs burn, chemicals known as karrikins are created in the smoke. When molecules of one particular karrikin come in contact with dormant seeds, they attach themselves to receptor sites on the protein responsible for germination. In doing so, the karrikin changes the protein’s shape, causing it to signal to other proteins to activate the genetic pathway regulating germination.