Characterization of the tomato Cf-4 gene for resistance to Cladosporium fulvum identifies sequences that determine recognitional specificity in Cf-4 and Cf-9.
AUTOR(ES)
Thomas, C M
RESUMO
In many interactions between plants and their pathogens, resistance to infection is specified by plant resistance (R) genes and corresponding pathogen avirulence (Avr) genes. In tomato, the Cf-4 and Cf-9 resistance genes map to the same location but confer resistance to Cladosporium fulvum through recognition of different avirulence determinants (AVR4 and AVR9) by a molecular mechanism that has yet to be determined. Here, we describe the cloning and characterization of Cf-4, which also encodes a membrane-anchored extracellular glycoprotein. Cf-4 contains 25 leucine-rich repeats, which is two fewer than Cf-9. The proteins have > 91% identical amino acids. DNA sequence comparison suggests that Cf-4 and Cf-9 are derived from a common progenitor sequence. Amino acid differences distinguishing Cf-4 and Cf-9 are confined to their N termini, delimiting a region that determines the recognitional specificity of ligand binding. The majority of these differences are in residues interstitial to those of the leucine-rich repeat consensus motif. Many of these residues are predicted to form a solvent-exposed surface that can interact with the cognate ligand. Both Cf-4 and Cf-9 are located within a 36-kb region comprising five tandemly duplicated homologous genes. These results provide further insight into the molecular basis of pathogen perception by plants and the organization of complex R gene loci.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=157069Documentos Relacionados
- Identification of Two Genes Required in Tomato for Full Cf-9-Dependent Resistance to Cladosporium fulvum.
- Domain Swapping and Gene Shuffling Identify Sequences Required for Induction of an Avr-Dependent Hypersensitive Response by the Tomato Cf-4 and Cf-9 Proteins
- Identification of Distinct Specificity Determinants in Resistance Protein Cf-4 Allows Construction of a Cf-9 Mutant That Confers Recognition of Avirulence Protein AVR4
- Developmentally regulated cell death on expression of the fungal avirulence gene Avr9 in tomato seedlings carrying the disease-resistance gene Cf-9.
- The biotrophic fungus Cladosporium fulvum circumvents Cf-4-mediated resistance by producing unstable AVR4 elicitors.