ABSTRACT
Species of the genus Lilium are well known for their large genomes. Although expansion of noncoding repeated DNA is believed to account for this genome size, retroelement del Ty3-gypsy is the only one described so far in the genus Lilium. We isolated Ty1-copia elements from Lilium longiflorum and named them LIREs (lily retrotransposons). The long terminal repeats, primer binding site, and polypurine tract sequences are highly similar among the LIRE elements, indicating that they are in the same lineage. Although the protein-coding regions were highly decayed, the sequence motifs of the integrase, reverse transcriptase, and RNase H domains were identifiable as belonging to the order of Ty1-copia elements. Phylogenetic analysis and primer binding site sequences revealed that these elements belonged to the Ale lineage among the six lineages of plant Ty1-copia elements. Base substitutions in the long terminal repeats estimated that the integration times of the LIRE Ty1-copia elements were between 0.7 and 5.5 mya. In situ hybridization showed that the LIRE elements were present in all the chromosomes of L. longiflorum and L. lancifolium, but absent in centromeres, telomeres, and 45S rRNA sites in both species. The LIRE elements were present very abundantly in species of the genus Lilium, but absent in other genera of the family Liliaceae, implying that the LIRE elements might have contributed to the expansion of the genome in the genus Lilium.
Subject(s)
DNA, Plant/genetics , Genome, Plant , Lilium/genetics , Retroelements , Amino Acid Sequence , Base Sequence , Binding Sites , Chromosomes, Plant , Evolution, Molecular , In Situ Hybridization, Fluorescence , Integrases/chemistry , Integrases/genetics , Molecular Sequence Data , Phylogeny , Plant Proteins/chemistry , Plant Proteins/genetics , RNA-Directed DNA Polymerase/chemistry , RNA-Directed DNA Polymerase/genetics , Ribonuclease H/chemistry , Ribonuclease H/genetics , Sequence Analysis, DNA , Terminal Repeat SequencesABSTRACT
The inheritance of extreme resistance to PVY (Ry (sto)) by a single dominant locus was confirmed by obtaining a 1:1 segregation ratio in a virus inoculation test with 28 resistant (Ryry) to 29 susceptible (ryry) anther culture-derived dihaploid lines (2n=2x=24) from cv. "Assia" (2n=4x=48) having extreme resistance derived from Solanum stoloniferum in simplex constitution (Ryryryry). Twelve Ry (sto) markers selected in AFLP assays using bulked segregant analysis were applied to 106 tested potato cultivars from Germany, The Netherlands and Poland and 19 potato cultivars were identified by these markers as extremely resistant to PVY in alignment with phenotypic data. The locus for extreme resistance (Ry (sto)) to PVY was mapped on chromosome XII co-segregating with the SSR marker STM 0003. The utility of anther-culture derived dihaploid potatoes for genetic marker development was demonstrated. Marker transferability from diploids to tetraploids provides an optimistic potential for marker-assisted selection in potato breeding programs.
