Open AccessThe AVR4 Elicitor Protein ofCladosporium fulvumBinds to Fungal Components with High Affinity
Author(s) -
Nienke Westerink,
Ronelle Roth,
H.A. van den Burg,
P.J.G.M. de Wit,
M.H.A.J. Joosten
Publication year - 2002
Publication title -
molecular plant-microbe interactions
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.565
H-Index - 153
eISSN - 1943-7706
pISSN - 0894-0282
DOI - 10.1094/mpmi.2002.15.12.1219
Subject(s) - cladosporium , elicitor , biology , biochemistry , microbiology and biotechnology , enzyme , aspergillus
The interaction between tomato and the fungal pathogen Cladosporium fulvum complies with the gene-for-gene system. Strains of C. fulvum that produce race-specific elicitor AVR4 induce a hypersensitive response, leading to resistance, in tomato plants that carry the Cf-4 resistance gene. The mechanism of AVR4 perception was examined by performing binding studies with 125 I-AVR4 on microsomal membranes of tomato plants. We identified an AVR4 high-affinity binding site (K D = 0.05 nM) which exhibited all the characteristics expected for ligand-receptor interactions, such as saturability, reversibility, and specificity. Surprisingly, the AVR4 high-affinity binding site appeared to originate from fungi present on infected tomato plants rather than from the tomato plants themselves. Detailed analysis showed that this fungus-derived, AVR4-specific binding site is heat- and proteinase K-resistant. Affinity crosslinking demonstrated that AVR4 specifically binds to a component of approximately 75 kDa that is of fungal origin. Our data suggest that binding of AVR4 to a fungal component or components is related to the intrinsic virulence function of AVR4 for C. fulvum.