title: The broad-spectrum tospovirus resistance gene Sw-5 of tomato is a homolog of the root-knot nematode resistance gene Mi.
abstract: We used a positional cloning approach to isolate the Sw-5 disease resistance locus of tomato. Complementation experiments with overlapping cosmid clones enabled us to demonstrate that Sw-5 is a single gene locus capable of recognizing several tospovirus isolates and species. Analysis of the predicted Sw-5 protein suggests that it is a cytoplasmic protein, with a potential nucleotide binding site (NBS) domain and a C-terminal end consisting of leucine-rich repeats (LRRs). Based on its structural features, Sw-5 belongs to the class of NBS-LRR resistance genes that includes the tomato Mi, 12, and Prf genes; the Arabidopsis RPM1 gene; and the plant potato virus X resistance gene Rx. The overall similarity between the Sw-5 and Mi proteins of tomato suggests that a shared or comparable signal transduction pathway leads to both virus and nematode resistance in tomato. The similarity also supports the hypothesis that Sw-5 provides resistance via a hypersensitive response. Sw-5 is a member of a loosely clustered gene family in the telomeric region of chromosome 9. Members of this family map to other regions of chromosome 9 and also to chromosome 12, where several fungal, virus, and nematode genes have been mapped, suggesting that paralogs of Sw-5 may have evolved to provide different resistance specificities.
authors.affiliation: Department of Plant Breeding, Cornell University, Ithaca NY 14853, USA.
authors.forename: S H
authors.initials: SH
authors.lastname: Brommonschenkel
authors.forename: A
authors.initials: A
authors.lastname: Frary
authors.forename: A
authors.initials: A
authors.lastname: Frary
authors.forename: S D
authors.initials: SD
authors.lastname: Tanksley
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002043:Bunyaviridae / Q000502:physiology*; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D003360:Cosmids; D018076:DNA, Complementary; D015870:Gene Expression; D017343:Genes, Plant; D005816:Genetic Complementation Test; D018551:Solanum lycopersicum / Q000235:genetics* / Q000469:parasitology / Q000821:virology*; D008969:Molecular Sequence Data; D005810:Multigene Family; D009348:Nematoda / Q000502:physiology; D010935:Plant Diseases / Q000235:genetics*; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics* / Q000502:physiology; D010942:Plant Viruses / Q000502:physiology*; D015398:Signal Transduction
chemical_list: D018076:DNA, Complementary; D010940:Plant Proteins; C419645:Sw-5 protein, Lycopersicon esculentum