The tomato Cf-5 disease resistance gene and six homologs show pronounced allelic variation in leucine-rich repeat copy number.
The tomato Cf-2 and Cf-5 genes confer resistance to Cladosporium fulvum and map to a complex locus on chromosome 6. The Cf-5 gene has been isolated and is predicted to encode a largely extracytoplasmic protein containing 32 leucine-rich repeats (LRRs), resembling the previously isolated Cf-2 gene, which has 38 LRRs. Three haplotypes of this locus from Lycopersicon esculentum, L. pimpinellifolium, and L. esculentum var cerasiforme were compared, and five additional homologs of Cf-5 were sequenced. All share extensive sequence identity, particularly within the C-terminal portions of the predicted proteins. In striking contrast to the Cf-9 gene family, six of seven homologs in the Cf-2/Cf-5 gene family vary in LRR copy number, ranging from 25 to 38 LRRs. Cf-5 and one adjacent homolog differ by only two LRRs. Recombination events that vary the LRR copy number in this region could provide a mechanism for the generation of new specificities for recognition of different ligands. A recombination breakpoint between the Cf-2 and Cf-5 loci was fully characterized and shown to be intragenic.
Dixon
M S
MS
Sainsbury Laboratory, John Innes Centre, Colney Lane, Norwich, NR4 7UH, United Kingdom.
Hatzixanthis
K
K
Jones
D A
DA
Harrison
K
K
Jones
J D
JD
D000483:Alleles; D000595:Amino Acid Sequence; D001483:Base Sequence; D002874:Chromosome Mapping; D002963:Cladosporium / Q000472:pathogenicity; D003001:Cloning, Molecular; D003360:Cosmids; D017931:DNA Primers / Q000235:genetics; D018744:DNA, Plant / Q000235:genetics; D019143:Evolution, Molecular; D017343:Genes, Plant; D005816:Genetic Complementation Test; D014644:Genetic Variation; D006239:Haplotypes; D018551:Solanum lycopersicum / Q000235:genetics* / Q000382:microbiology*; D008969:Molecular Sequence Data; D010935:Plant Diseases / Q000235:genetics* / Q000382:microbiology*; D030821:Plants, Genetically Modified; D016133:Polymerase Chain Reaction; D011995:Recombination, Genetic; D017386:Sequence Homology, Amino Acid
D017931:DNA Primers; D018744:DNA, Plant