Characterization of the tomato Cf-4 gene for resistance to Cladosporium fulvum identifies sequences that determine recognitional specificity in Cf-4 and Cf-9.
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.
Thomas
C M
CM
Sainsbury Laboratory, John Innes Centre, Norwich, United Kingdom.
Jones
D A
DA
Parniske
M
M
Harrison
K
K
Balint-Kurti
P J
PJ
Hatzixanthis
K
K
Jones
J D
JD
D000595:Amino Acid Sequence; D001483:Base Sequence; D002963:Cladosporium / Q000472:pathogenicity*; D003001:Cloning, Molecular; D017931:DNA Primers / Q000235:genetics; D018744:DNA, Plant / Q000235:genetics; D017343:Genes, Plant; D005816:Genetic Complementation Test; D008024:Ligands; D018551:Solanum lycopersicum / Q000235:genetics* / Q000378:metabolism / Q000382:microbiology*; D008562:Membrane Glycoproteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D010935:Plant Diseases / Q000235:genetics / Q000382:microbiology; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D016133:Polymerase Chain Reaction; D017434:Protein Structure, Tertiary; D011995:Recombination, Genetic; D014774:Virulence / Q000235:genetics
C109609:Cf protein, Lycopersicon esculentum; D017931:DNA Primers; D018744:DNA, Plant; D008024:Ligands; D008562:Membrane Glycoproteins; D010940:Plant Proteins