DAMP In Plants

DAMP in plantsResearchers at the Boyce Thompson Institute (BTI) have recently reported that a protein that signals tissue damage to the human immune system has a counterpart that plays a similar role in plants.  They 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, a protein that researchers call HMGB3.  Knowledge of HMGB3 and its human equivalent, HMGB1, allows us to better understand how humans and plants can fight off infections.

Plants and animal tissues use DAMPs to detect when they’re wounded 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.  Researchers found that the actions of HMGB3 through their investigations of plant and animal proteins that interact with salicylic acid, a plant immune regulator and the main breakdown product of aspirin.  A previous study by these researchers found that the salicylic acid blocks HMGB1, a DAMP in humans associated with multiple inflammation-related diseases.  When they searched the genome of the model plant Arabidopsis for genes coding for similar proteins, they found HMGB3.

The researchers then compared the actions of HMGB3 in Arabidopsis plants to other known plant DAMPs, then measured the protein’s ability to help plants fight off gray mold infection.  After injecting the protein into the extracellular space of the plant, they found that it triggered a signaling cascade involved in the plant immune response, activated the expression of genes involved in defense, started callose deposition and made the plants more resistant to gray mold infection.  They discovered that much like HMGB1, HMGB3 interacts with salicylic acid, which inhibits it activities.  The immune-boosting effects of HMGB3 in gray mold-infected plants were erased when the researchers added salicylic acid.

The findings of this study help the researchers better translate what has been learned in one system to the other, and in future work they intend to continue looking into targets of salicylic acid shared by plants and animals, which have a major role in disease.

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