When microbes invade, a plant launches an elaborate defense, and somehow the plant's own cells turn up dead. Biologists are unraveling the scheme—a plot with more twists than any movie of the week.

An unknown chemical triggers the death. Whatever the chemical's identity, when there's enough of it, it gives the gene the nod to carry out the plot.

Within hours, the plant's cells are dead.

This isn't your routine hit. When a plant bumps off its own cells this way, it's part of a resistance response—the plant battling a fungus or other microscopic pathogen. We've all seen the evidence on leaves—tiny flecks or holes scientists call "lesions." continue story