Jeffrey Dangl and his research team at the Howard Hughes Medical Institute (HHMI) have discovered the mechanism that plants use to self-destruct in order to survive.
Plant cells self-destruct to survive. When they detect a pathogen, they set off a chain reaction that ultimately destroys them, preventing the disease from spreading. Dangl's team discovered the mechanism behind this self-destruction. They found that plant defense proteins cluster together to pierce the cell membrane, opening a channel into the infected cell. Calcium then floods in, ultimately killing the cell.
The team studied NLR proteins that detect specific pathogen molecules. They used x-ray crystallography to take detailed pictures of the NLR protein's structure. They then made targeted mutations to the protein, to see how changes in various places affected its function. The team tested different versions of the protein and how they behaved in cells and lab dishes and pieced together a picture of its mode of action.
They found that in the presence of a pathogen, NLR proteins merge into a mega-protein. Part of the protein forms a funnel-like structure that pokes into the membrane of an infected cell, creating a channel that lets calcium into the cell. Because high levels of calcium are toxic, an influx can mean death for the cell.
(Source: Crop Biotech Update, International Service for Acquisition of Agri-Biotech Applications.

Activated plant immune proteins (pink) move to the cell membrane (left panel). When inactive, these proteins spread throughout the cell (right). The overlay (green and blue ribbons) shows the protein structure that pierces the cell membrane to form a channel. Photo Credit: Dr. Farid El Kasmi