RESUMEN
Mi-1, a Lycopersicon peruvianum gene conferring resistance to the agricultural pests, root-knot nematodes, and introgressed into tomato, has been cloned using a selective restriction fragment amplification based strategy. Complementation analysis of a susceptible tomato line with a 100 kb cosmid array yielded a single cosmid clone capable of conferring resistance both to the root-knot nematode Meloidogyne incognita and to an unrelated pathogen, the potato aphid Macrosiphum euphorbiae. This resistance was stable. The Mi-1 gene encodes a protein sharing structural features with the nucleotide-binding site leucine-rich repeat-containing type of plant resistance genes.
Asunto(s)
Áfidos , Genes de Plantas , Nematodos , Proteínas de Plantas/genética , Solanum lycopersicum/genética , Solanum tuberosum/parasitología , Secuencia de Aminoácidos , Animales , Clonación Molecular , Cósmidos , Prueba de Complementación Genética , Solanum lycopersicum/parasitología , Datos de Secuencia Molecular , Proteínas de Plantas/químicaRESUMEN
The I2 locus in tomato confers resistance to race 2 of the soil-borne fungus Fusarium oxysporum f sp lycopersici. The selective restriction fragment amplification (AFLP) positional cloning strategy was used to identify I2 in the tomato genome. A yeast artificial chromosome (YAC) clone covering approximately 750 kb encompassing the I2 locus was isolated, and the AFLP technique was used to derive tightly linked AFLP markers from this YAC clone. Genetic complementation analysis in transgenic R1 plants using a set of overlapping cosmids covering the I2 locus revealed three cosmids giving full resistance to F. o. lycopersici race 2. These cosmids shared a 7-kb DNA fragment containing an open reading frame encoding a protein with similarity to the nucleotide binding site leucine-rich repeat family of resistance genes. At the I2 locus, we identified six additional homologs that included the recently identified I2C-1 and I2C-2 genes. However, cosmids containing the I2C-1 or I2C-2 gene could not confer resistance to plants, indicating that these members are not the functional resistance genes. Alignments between the various members of the I2 gene family revealed two significant variable regions within the leucine-rich repeat region. They consisted of deletions or duplications of one or more leucine-rich repeats. We propose that one or both of these leucine-rich repeats are involved in Fusarium wilt resistance with I2 specificity.
Asunto(s)
Mapeo Cromosómico , Proteínas de Unión al ADN/genética , Fusarium/patogenicidad , Genes de Plantas , Familia de Multigenes , Solanum lycopersicum/genética , Solanum lycopersicum/microbiología , Secuencia de Aminoácidos , Secuencia de Bases , Cromosomas Artificiales de Levadura , Cósmidos , Cartilla de ADN , Proteínas de Unión al ADN/biosíntesis , Proteínas de Unión al ADN/química , Amplificación de Genes , Genoma de Planta , Inmunidad Innata/genética , Datos de Secuencia Molecular , Proteínas de Plantas/genética , Reacción en Cadena de la Polimerasa , Mapeo Restrictivo , Alineación de Secuencia , Homología de Secuencia de AminoácidoRESUMEN
From a potato genomic library a phage lambda clone was isolated that carried nucleotide sequences of two patatin genes, thus demonstrating a close physical linkage between these two members of the patatin gene family. Sequence and restriction analysis showed the genes to be oriented in tandem. The more upstream gene was a pseudogene truncated at the 3' end, whereas the downstream gene was a class II patatin gene. In addition to a 208 bp fragment also present in patatin class I promoters, the region in between both genes contained various direct repeats also found in other patatin genes. To study the promoter activity of this intergenic region, a 2.78 kb fragment was transcriptionally fused to the beta-glucuronidase gene and reintroduced into potato cultivar Bintje. Histochemical analysis revealed expression in the outermost layer of cells of the cortex, in the tuber phellogen, in or around the root vascular system, and also in the abaxial phloem layer of the vascular bundle in leaves.