title: Dissection of the fusarium I2 gene cluster in tomato reveals six homologs and one active gene copy.
abstract: 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.
authors.affiliation: Keygene N.V., Agro Business Park 90, P.O. Box 216, 6700 AE Wageningen, The Netherlands. keygene@euronet.nl
authors.forename: G
authors.initials: G
authors.lastname: Simons
authors.forename: J
authors.initials: J
authors.lastname: Groenendijk
authors.forename: J
authors.initials: J
authors.lastname: Wijbrandi
authors.forename: M
authors.initials: M
authors.lastname: Reijans
authors.forename: J
authors.initials: J
authors.lastname: Groenen
authors.forename: P
authors.initials: P
authors.lastname: Diergaarde
authors.forename: T
authors.initials: T
authors.lastname: Van der Lee
authors.forename: M
authors.initials: M
authors.lastname: Bleeker
authors.forename: J
authors.initials: J
authors.lastname: Onstenk
authors.forename: M
authors.initials: M
authors.lastname: de Both
authors.forename: M
authors.initials: M
authors.lastname: Haring
authors.forename: J
authors.initials: J
authors.lastname: Mes
authors.forename: B
authors.initials: B
authors.lastname: Cornelissen
authors.forename: M
authors.initials: M
authors.lastname: Zabeau
authors.forename: P
authors.initials: P
authors.lastname: Vos
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D002874:Chromosome Mapping; D018244:Chromosomes, Artificial, Yeast; D003360:Cosmids; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics*; D005670:Fusarium / Q000472:pathogenicity*; D005784:Gene Amplification; D017343:Genes, Plant; D018745:Genome, Plant; D007113:Immunity, Innate / Q000235:genetics; D018551:Solanum lycopersicum / Q000235:genetics* / Q000382:microbiology*; D008969:Molecular Sequence Data; D005810:Multigene Family; D010940:Plant Proteins / Q000235:genetics; D016133:Polymerase Chain Reaction; D015183:Restriction Mapping; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
chemical_list: D017931:DNA Primers; D004268:DNA-Binding Proteins; C106157:I2C protein, Lycopersicon esculentum; D010940:Plant Proteins