A High-Affinity Binding Site for the AVR9 Peptide Elicitor of Cladosporium fulvum Is Present on Plasma Membranes of Tomato and Other Solanaceous Plants.

Abstract

The race-specific Cladosporium fulvum peptide elicitor AVR9, which specifically induces a hypersensitive response in tomato genotypes carrying the Cf-9 resistance gene, was labeled with iodine-125 at the N-terminal tyrosine residue and used in binding studies. 125I-AVR9 showed specific, saturable, and reversible binding to plasma membranes isolated from leaves of tomato cultivar Moneymaker without Cf resistance genes (MM-Cf0) or from a near-isogenic genotype with the Cf-9 resistance gene (MM-Cf9). The dissociation constant was found to be 0.07 nM, and the receptor concentration was 0.8 pmol/mg microsomal protein. Binding was highly influenced by pH and the ionic strength of the binding buffer and by temperature, indicating the involvement of both electrostatic and hydrophobic interactions. Binding kinetics and binding capacity were similar for membranes of the MM-Cf0 and MM-Cf9 genotypes. In all solanaceous plant species tested, an AVR9 binding site was present, whereas in the nonsolanaceous species that were analyzed, such a binding site could not be identified. The ability of membranes isolated from different solanaceous plant species to bind AVR9 seems to correlate with the presence of members of the Cf-9 gene family, but whether this correlation is functional remains to be determined.

A Single Binding Site Mediates Resistance- and Disease-Associated Activities of the Effector Protein NIP1 from the Barley Pathogen Rhynchosporium secalis

“…This suggests that the binding site represents the virulence target of NIP1, which appears to be common in cereals. Similar results were obtained with the AVR9 elicitor from C. fulvum, for which binding sites are also present in plasma membranes from resistant (Cf-9) and susceptible (Cf-0) tomato genotypes, as well as from other solanaceous species (Kooman-Gersmann et al, 1996).…”

“…For the fungal phytotoxin fusicoccin, a concentration 100-fold higher than the K d of 1 nM was necessary to stimulate the plant plasma membrane H 1 -ATPase (Basel et al, 1994). An even larger difference (approximately 4,000-fold) between K d value and the minimal elicitor concentration required for inducing a hypersensitive response in tomato leaves was described for the AVR9 elicitor from C. fulvum (Kooman-Gersmann et al, 1996). However, the quantitative comparison of affinities and activities needs to be interpreted with caution.…”

“…These latter motifs also occur in Ser-Thr receptor kinases involved in specific recognition of nod factors (Radutoiu et al, 2003;Knogge and Scheel, 2006). Very low K d values of 0.07 and 0.05 nM, respectively, were described for the Avr gene products AVR9 and AVR4 from the tomato pathogen C. fulvum (Kooman-Gersmann et al, 1996). Whereas the plantbinding site for AVR9 remains to be characterized, AVR4 was shown to bind to fungus-derived nonproteinaceous components (Westerink et al, 2002) and with lower affinity to chitin fragments (DP 5 6; K d 5 6.3 mM; van den Burg et al, 2004).…”

“…For the Pep-13 elicitor from P. sojae, 88 fmol 3 mg 21 were found in parsley cells (Nü rnberger et al, 1994), for different elicitins in tobacco, 234 to 403 fmol 3 mg 21 (Bourque et al, 1998), for the hepta-b-glucoside from P. sojae in soybean cells, 1.2 pmol 3 mg 21 (Cheong and Hahn, 1991;Cosio et al, 1998), for chitin fragments in tomato, 2.45 pmol 3 mg 21 (Baureithel et al, 1994), and for soybean cells and roots, 7.6 to 12.2 pmol 3 mg 21 (Day et al, 2001). In comparison, the number of binding sites for the AVR9 elicitor from C. fulvum on tomato membranes is 800 fmol 3 mg 21 (Kooman-Gersmann et al, 1996).…”

The Receptor for the Fungal Elicitor Ethylene-Inducing Xylanase Is a Member of a Resistance-Like Gene Family in Tomato

“…Similarly, interaction between the cytoplasmic receptor Pi-ta and the corresponding AVR-Pita is required to induce resistance response (Jia et al, 2000). While these interactions are crucial for plant defense induction, the Avr9 elicitor exhibits high affinity binding to plasma membranes isolated from both resistant and susceptible tomato (Lycopersicon esculentum) cultivars (Kooman-Gersmann et al, 1996;Luderer et al, 2001).…”