The rice XA21 immune receptor is activated upon recognition of the tyrosine sulfated peptide, RaxX (required for activation of XA21-mediated immunity X) produced by Xanthomonas oryzae pv. oryzae (Xoo). RaxX shares remarkable similarity to the plant hormone PSY (plant peptide containing sulfated tyrosine) family and mimics PSY’s growth promotion activity.
We have hypothesized that sulfated RaxX is processed and secreted by RaxABC type I secretion system to manipulate host cellular processes. Here, our mutational studies and targeted proteomics revealed that the RaxX precursor peptide (proRaxX) is processed and secreted by the protease/transporter RaxB, whose function can be partially fulfilled by a noncognate peptidase-containing transporter B (PctB). proRaxX is cleaved at a Gly-Gly motif, yielding a mature peptide that retains the necessary elements for RaxX function as an immunogen and host peptide hormone mimic. These results indicate that RaxX is the first prokaryotic member of a previously unclassified and understudied group of eukaryotic tyrosine sulfated RiPPs (ribosomally synthesized, post-translationally modified peptides). We further demonstrate that sulfated RaxX directly binds XA21 with high affinity. We will present a complete, previously uncharacterized biological process: bacterial RiPP biosynthesis, secretion, binding to a eukaryotic receptor and triggering of a robust host immune response.
The biennial Congress on Molecular Plant-Microbe Interactions is a major function of IS-MPMI. This is an excellent opportunity to learn and share with all of the international members. The Congress has been held throughout the world, with locations varying from, most recently, U.S., Greece, Japan, Italy, Mexico, and Russia. Always well attended, the Congress speaks to the vitality of IS-MPMI and the important role this meeting plays in helping facilitate the important work of our members.
The rice XA21 immune receptor is activated upon recognition of the tyrosine sulfated peptide, RaxX (required for activation of XA21-mediated immunity X) produced by Xanthomonas oryzae pv. oryzae (Xoo). RaxX shares remarkable similarity to the plant hormone PSY (plant peptide containing sulfated tyrosine) family and mimics PSY’s growth promotion activity.
We have hypothesized that sulfated RaxX is processed and secreted by RaxABC type I secretion system to manipulate host cellular processes. Here, our mutational studies and targeted proteomics revealed that the RaxX precursor peptide (proRaxX) is processed and secreted by the protease/transporter RaxB, whose function can be partially fulfilled by a noncognate peptidase-containing transporter B (PctB). proRaxX is cleaved at a Gly-Gly motif, yielding a mature peptide that retains the necessary elements for RaxX function as an immunogen and host peptide hormone mimic. These results indicate that RaxX is the first prokaryotic member of a previously unclassified and understudied group of eukaryotic tyrosine sulfated RiPPs (ribosomally synthesized, post-translationally modified peptides). We further demonstrate that sulfated RaxX directly binds XA21 with high affinity. We will present a complete, previously uncharacterized biological process: bacterial RiPP biosynthesis, secretion, binding to a eukaryotic receptor and triggering of a robust host immune response.
The biennial Congress on Molecular Plant-Microbe Interactions is a major function of IS-MPMI. This is an excellent opportunity to learn and share with all of the international members. The Congress has been held throughout the world, with locations varying from, most recently, U.S., Greece, Japan, Italy, Mexico, and Russia. Always well attended, the Congress speaks to the vitality of IS-MPMI and the important role this meeting plays in helping facilitate the important work of our members.