Figure: Damage caused on tomato plants upon infection with Pseudomonas syringe bacteria. © Chris Smart, NYSAES, Geneva NY

An international research team led by Heribert Hirt from King Abdullah University of Science and Technology (KAUST) has found the missing link in the complex molecular pathway by which plants resist pathogens.

Using Arabidopsis, the team activated mitogen-activated protein kinases (MAPKs) using a bacterial microbial-associated molecular patterns (MAMPs). In a series of experiments, they searched for phophorylation events and found that the final MAPK-MAPK in the chain which is MPK3, phosphorylates the enzyme histone deacetylase (HD2B), which regulates DNA compaction into chromatin.

The team showed that in Arabidopsis plants that lack MPK3 or HD2B, many defense genes increased in activity, suggesting that HD2B represses gene activity. When pathogens attack, MPK3's action on HD2B reverses this repression.

Hirt said that kinase-triggered chromatin reprogramming is a widespread mechanism, and considers possibilities for artificially stimulating this process. "Once we better understand the mechanism of inducing pathogen memory, we might be able to induce long-term resistance, similar to human vaccination," he added.

For more details, read the KAUST Discovery.