This process is called cell death response and ensures that only a few host cells die. Tomatoes use this mechanism when they are attacked by a bacterial pathogen known as Pseudomonas syringae pv. tomato, which causes speck disease.
In a study at Boyce Thompson Institute, scientists introduce a protein, called Mai1, which plays a role in this missing link. They found that when the expression of Mai1 is muted, the plants could no longer defend themselves against pathogens using the cell death response. As a result, these plants were more susceptible to bacterial infection.
The identification of this protein as a central regulator of immunity in tomato has advanced the understanding of plant signaling mechanisms. The research suggests that Mai1 has a central role in immunity that likely can not be substituted by other proteins.