ABSTRACT
In tomato, Ve is implicated in race-specific resistance to infection by Verticillium species causing crop disease. Characterization of the Ve locus involved positional cloning and isolation of two closely linked inverted genes. Expression of individual Ve genes in susceptible potato plants conferred resistance to an aggressive race 1 isolate of Verticillium albo-atrum. The deduced primary structure of Ve1 and Ve2 included a hydrophobic N-terminal signal peptide, leucine-rich repeats containing 28 or 35 potential glycosylation sites, a hydrophobic membrane-spanning domain, and a C-terminal domain with the mammalian E/DXXXLphi or YXXphi endocytosis signals (phi is an amino acid with a hydrophobic side chain). A leucine zipper-like sequence occurs in the hydrophobic N-terminal signal peptide of Ve1 and a Pro-Glu-Ser-Thr (PEST)-like sequence resides in the C-terminal domain of Ve2. These structures suggest that the Ve genes encode a class of cell-surface glycoproteins with receptor-mediated endocytosis-like signals and leucine zipper or PEST sequences.
Subject(s)
Genes, Plant/physiology , Leucine Zippers , Membrane Glycoproteins/genetics , Plant Proteins/genetics , Receptors, Cell Surface/genetics , Solanum lycopersicum/genetics , Verticillium/physiology , Amino Acid Sequence , Cloning, Molecular , Gene Expression , Genetic Complementation Test , Genome, Plant , Membrane Glycoproteins/physiology , Molecular Sequence Data , Plant Proteins/physiology , Plants, Genetically Modified , Receptors, Cell Surface/physiology , Solanum tuberosum/microbiologyABSTRACT
Resistance to verticillium wilt, a vascular disease causing yield losses in many crops, is conferred in tomato by a single dominant allele, Ve. A population segregating for the Ve allele was generated using near-isogenic tomato lines. Analysis of the parental tomato DNA using the polymerase chain reaction and 400 random primers, each 10 deoxyribonucleotides in length, produced 1,880 amplified DNA fragments. Of the four polymorphisms observed between the resistant and susceptible parental genotypes, only one was linked to the Ve gene. No recombination was observed between this DNA marker and the Ve locus, indicating that the linkage is less than 3.5±2.7 cM. The marker detected both the susceptible and resistant alleles, producing amplified DNA fragments of approximately 1,300 and 1,350 bp, respectively. The sequence of the primer, determined from cloned amplified products, was 5' CTCACATGCA 3' instead of the expected 5' CTCACATGCC 3'. The marker will be of value to tomato breeding programs because of the tight linkage, Codominant nature, and analytical procedure utilized.
