title: The Mi-9 gene from Solanum arcanum conferring heat-stable resistance to root-knot nematodes is a homolog of Mi-1.
abstract: Resistance conferred by the Mi-1 gene from Solanum peruvianum is effective and widely used for limiting root-knot nematode (Meloidogyne spp.) yield loss in tomato (Solanum lycopersicum), but the resistance is ineffective at soil temperatures above 28 degrees C. Previously, we mapped the heat-stable resistance gene Mi-9 in Solanum arcanum accession LA2157 to the short arm of chromosome 6, in a genetic interval as Mi-1 and the Cladosporium fulvum resistance gene Cf2. We developed a fine map of the Mi-9 region by resistance and marker screening of an F2 population and derived F3 families from resistant LA2157 x susceptible LA392. Mi-1 intron 1 flanking primers were designed to amplify intron 1 and fingerprint Mi-1 homologs. Using these primers, we identified seven Mi-1 homologs in the mapping parents. Cf-2 and Mi-1 homologs were mapped on chromosome 6 using a subset of the F2. Cf-2 homologs did not segregate with Mi-9 resistance, but three Mi-1 homologs (RH1, RH2, and RH4) from LA2157 and one (SH1) from LA392 colocalized to the Mi-9 region. Reverse transcriptase-polymerase chain reaction analysis indicated that six Mi-1 homologs are expressed in LA2157 roots. We targeted transcripts of Mi-1 homologs for degradation with tobacco (Nicotiana tabacum) rattle virus (TRV)-based virus-induced gene silencing using Agrobacterium infiltration with a TRV-Mi construct. In most LA2157 plants infiltrated with the TRV-Mi construct, Mi-9-mediated heat-stable root-knot nematode resistance was compromised at 32 degrees C, indicating that the heat-stable resistance is mediated by a homolog of Mi-1.
authors.affiliation: Department of Nematology, University of California, Riverside, California 92521, USA.
authors.forename: Barbara
authors.initials: B
authors.lastname: Jablonska
authors.forename: Jetty S S
authors.initials: JS
authors.lastname: Ammiraju
authors.forename: Kishor K
authors.initials: KK
authors.lastname: Bhattarai
authors.forename: Sophie
authors.initials: S
authors.lastname: Mantelin
authors.forename: Oscar
authors.initials: O
authors.lastname: Martinez de Ilarduya
authors.forename: Philip A
authors.initials: PA
authors.lastname: Roberts
authors.forename: Isgouhi
authors.initials: I
authors.lastname: Kaloshian
mesh_terms: D000818:Animals; D002874:Chromosome Mapping; D032461:Chromosomes, Plant; D018506:Gene Expression Regulation, Plant / Q000502:physiology*; D020868:Gene Silencing; D006358:Hot Temperature; D010802:Phylogeny; D010935:Plant Diseases / Q000469:parasitology; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism*; D032322:Solanum / Q000235:genetics* / Q000378:metabolism*; D014431:Tylenchoidea / Q000502:physiology*
chemical_list: C117349:MI-1 protein, Lycopersicon esculentum; D010940:Plant Proteins