Discovery Shows Parallels Between Plant and Human Immune Systems

Researchers at the Boyce Thompson Institute (BTI) report that a protein that signals tissue damage to the human immune system has a counterpart that plays a similar role in plants. Professor Daniel Klessig and his colleagues have identified a new damage-associated molecular pattern molecule or "DAMP" in plants. DAMP molecules released by injured cells trigger an immune response in plants and animals. The protein, HMGB3, and its human equivalent, HMGB1, enhances understanding of how humans and plants fight off infections.

Plants and animal tissues use DAMPs to detect injury, so that they can promote healing and fend off infection. DAMPs are always present inside cells, but are released into the surrounding space in response to tissue damage, where they activate inflammatory and immune responses.

The team discovered the actions of HMGB3 through their research work on plant and animal proteins that interact with salicylic acid, a plant immune regulator and the main breakdown product of aspirin. A previous study by Klessig's lab found that salicylic acid blocks HMGB1, and when they searched the genome of the model plant Arabidopsis for genes coding for similar proteins, they found HMGB3. The researchers injected the protein into the extracellular space of the plant and examined the different layers of immune activity. They found that like human HMGB1, HMGB3 also interacts with salicylic acid, which inhibits its activities. The immune-boosting effects of HMGB3 in gray mold-infected plants were erased when the researchers added salicylic acid.

More details of the research are available at the BTI website.