| Comment | This family consists of proteins closely related to Ax21 (Activator of XA21-mediated immunity), a protein that is secreted by a type I secretion system (RaxABC), and that appears to be sulfated on an N-terminal region tryosine in a motif LSYN. Ax21 acts in a quorum-sensing system. Homologous peptide-mediated quorum-sensing systems appear to exist in other species, such as the emerging opportunistic pathogen Stenotrophomonas maltophilia. Intriguingly, the rice genome encodes a receptor (XA21) for this protein that triggers innate immunity. |
