The Secret Weapon of Friendly Root Bacteria: A Unique Protein

A tiny world underground, where plant roots meet and greet a crowd of microorganisms called the rhizosphere microbiome. Some of these microbes can trigger the plant's immune system—like when they detect flg22, a snippet from the flagellin protein found on bacterial cells. However, a few commensal (friendly) bacteria have learned to suppress this immune reaction.Scientists explored this phenomenon by studying 165 root-associated bacteria, focusing on one specific strain, Dyella japonica MF79. They found that this strain produces a unique protein called immunosuppressive subtilase A (IssA). IssA is like a tiny scissor that cuts the flg22 molecule, leaving the plant's immune system unaware of the bacteria's presence and allowing the plant to grow undisturbed. Interestingly, IssA isn't exclusive to Dyella japonica MF79. Other plant-associated microbes produce similar proteins, especially those belonging to the Xanthomonadales order. This discovery reveals a fascinating technique used by commensal microbes to manage the plant's immune response.