Sulfated peptides serve as molecular mimics that facilitate pathogen virulence

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This work will advance understanding of how bacteria and nematodes infect plants. Specifically, the researchers will study a group of molecules that are predicted to play important roles in plant growth, development, and defense, which are critical to crop quality and yield. Because bacteria and nematodes infect a wide range of plants and these molecules are present in virtually all crop plants, successful completion of the proposed objectives will have broad significance to U.S. agriculture. This work will provide interdisciplinary training of postdoctoral researchers and mentoring of undergraduate and high school students on cutting-edge technologies of genetics, proteomics, and molecular biology. Diverse species of plant pathogens secrete molecules that mimic those produced by the host as a strategy to manipulate host cellular function. For example, the rice pathogen Xanthomonas oryzae pv. oryzae (Xoo) secretes a microbial peptide called RaxX, which is required for activation of rice XA21-mediated immunity. RaxX shares sequence similarity to the plant peptide containing sulfated tyrosine (PSY) family, which is critical for plant growth and development. RaxX is conserved in multiple Xanthomonas species and can promote root growth to the same extent as the host PSY peptide. Null mutation of raxX compromises the virulence of Xoo on rice plants that lack the XA21 immune receptor. Together, these results suggest that RaxX functions as a bacterial virulence factor. The researchers discovered that the genomes of the root-knot nematode, of the Meloidogyne incognita group, are also predicted to contain genes for PSY-like peptides (named MigPSY). In Arabidopsis, PSY promotes cellular proliferation and expansion. Considering that formation of the nematode feeding site requires extensive host cell expansion and cell wall modifications, we hypothesize that root-knot nematodes utilize MigPSY to commandeer host PSY signaling to manipulate cellular proliferation and remodeling during feeding site formation. This proposal aims to test this hypohtesis. This project will (1) analyze the expression and bioactivity of PSY-like peptides, (2) investigate how PSY-like signaling contributes to successful bacterial and nematode infection, and (3) identify plant receptors involved in this signaling response.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.